Text © DrSc Giuliano Russini – Biologist Zoologist
English translation by Mario Beltramini
The order of the Primates, eutherian mammals, placentate (from the Latin “Primates” or “Primus”: the best), forms one of the animal orders more complicated, debated and controversial, on which the biologists have discussed and still are ardently discussing since more than 150 years.
Such complexity of study comes from a sort of reverence the students had, mainly in the past, for these animals and which is still persisting, at least partly, for various reasons.
This mainly because, till the second half of the twentieth century, they were considered as our direct progenitors, whilst nowadays, as we shall see, the zoological scientific community sees them rather as our cousins: species with which we share a common anthropoid progenitor. A forefather from which both descend and whose existence, even if specific fossil skeletons have not yet been discovered, seems to be almost certain after complex phylogenetic analyses.
The study of these animals is somewhat recent if compared with that of other orders.
We must think that the first specimens of Western Gorilla (Gorilla gorilla), were discovered in the tropical forests of the Congolese highlands and on the mountains close to the Niger river, only in 1835, during the continuous expeditions and explorations of the zoological biologists in the continent of Africa, which till the first half of the nineteenth century, was indicated on the maps under the name of “Hic sunt leones” (from Latin: here are the lions), seen that the (Panthera leo) was representing the main faunal characteristic, as it had been the first time that such a big, ferocious and dangerous feline had been discovered.
Obviously, both African flora and fauna, but also those of Asia and Americas, in the following years, would have revealed, and still do, thousands of curious and scientifically original species to the biologists’ eyes, thus enriching the kaleidoscopic world of Botany and Zoology.
Indeed, the sensibility and attention paid to the study of these animals by the zoologist biologists, was at first attracted by the exposition made by the English biologist Charles Darwin about the theory on the Origin of Species, published in “On the Origin of Species, by means Natural Selection, or the preservation of favoured Races in the struggle of Life” on 1859, theory which was proposed, almost at the same time, also by another English biologist, Alfred Russel Wallace.
The two scientists had reached the same conclusions, independently, after working in different geographic areas of the terrestrial globe: C. Darwin in the Galapagos, in the Pacific Ocean, whilst A.R. Wallace was in Indonesia and in the Indian Ocean.
Other two books by Darwin followed this first opus, “The variation of animals and plants under domestication” in 1868 and “The Descent of Man and selection in relation to Sex”, published in 1871.
In all the three books Darwin declared (thing on which he much meditated and hesitated as, when doing so, he would have caused the rage of the so much powerful by that time, ecclesiastical world) that “the human being and all the races in which he subdivides, were to be considered as direct descendants of the monkeys”, that is of the primates, like, for instance, the Chimpanzee (Pan troglodytes).
As expected, the publication of this theory arose the rage of the Christian-catholic world and of the Anglican one, to such a point that Charles Darwin was accused of heresy and was put on trial, in which he had to demonstrate the correctness of such arrogant theses which were going against the creationist theory, supported by the Church, as written in the Bible, after which, synthetically: “the human being has been created in God’s own image and likeness”.
From this, for transitive property and following the Darwinian thought, it was deducted that either God was a monkey, or that his “opera magna”, the human being, around whom were rotating all other living beings, was similar to a rude, crude and devoid of intellect animal, like a primate.
Obviously, this sort of declaration was not absolutely in the intentions of the English biologist.
First of all, because C. Darwin was a believer himself, and had nothing against the church, and then because the aim of a scientist like him, was simply to observe the wonders of nature and to humbly try, with a theory, to explain what in reality nature has done, does and will go on in doing.
This placed in a dimension standing well over whatever sceptic preconceived and limited human judgement, starting from the fact that we are not at the centre of the universe, but we are a very small part of the same, one of the many guests present on this planet.
Close to the end of his life, Darwin confided to a friend: “I did not think that a humble biologist like me, who has spent all his life among fossils, animals and plants, might create such an ado, with a series of ideas, with a small theory, which is simply what I believe to be a part of the logic of nature”.
The most obstinate defender of Darwin was the English biologist T.H. Huxley (nicknamed Darwin’s Bulldog), who defended the father of the evolution and his theory at the trial organized by the church against him, to which he was absent due to the death of his son, passed away due to scarlet fever.
T.H. Huxley evidenced in a very elegant way the obtuseness of the prelates towards the science and the progress, and their atavistic fears towards people rationality and autonomy of thought.
Back to our times and begging pardon to my fellow biologists for this concise summary on how did Charles Darwin vicissitude went, premise in any case needed for understanding which was the spring snapping the extreme interest for studying this animal group, we can say that the ranks of the zoologist biologists have added other types of biologists, such as the physical anthropologists, paleoanthropologists, the evolution biologists and, obviously, the primatologists.
Shortly after the enunciation of C. Darwin’s theory, two basic schools of thought came to life, the first where the members saw the direct descent of the human being from the apes as obvious, so much that the Chimpanzee (Pan troglodytes), the Gorilla (Gorilla gorilla) or the Orang-utan (Pongo pygmaeus), represented after them, primitive men at different stages of evolution, which had remained isolated inside the African and Asiatic tropical forests and where might be read the first proto-traces of the human intelligence, evidenced by their manual abilities, like in the instance of the chimpanzee when the same utilizes a small stick for collecting ants or termites inside their nest.
The second school, on the contrary, thought that these ones were animals whose evolution development had been interrupted, for ecologic reasons and for geographic isolation, at the stage immediately preceding the human one.
Later, the discovery of several primates, of fossil skeletons of various types of Hominids (family: Hominidae) concerning different eras, with the contemporaneous paleo-genetic, paleontologic analyses of these last ones and of several species of monkeys, has induced the primatologists, mainly the biologist Prof. Jonathan Kingdon of Oxford, the biologist Prof. Elisabetta Visalberghi of Rome, the biologist Patrizia Messeri of Florence and, obviously, the biologist Jane Goodall, the top authorities on the subject, to assume that the human-hominids being and the anthropoid-anthropomorphic apes have a common ancestor, from whom two descendent branches have developed.
One has completed (at least for now) its evolution development in the present anthropomorphic forms, whilst the other one has brought, about 40.000 years ago, after a way lasted about 1-2 millions of years, to the birth of the Homo sapiens, from whom we directly come, as the Homo sapiens sapiens is one of his races or subspecies.
So, nowadays, most of the biologists assume that the human being and the apes are cousins, and not one descendant of the other, and that the famous Darwinian missing ring, the one which should connect man to monkey, is in reality represented by us, human beings.
Primates and Hominidae, a look into their Natural and Evolutionary History
Since about 65-70 millions of years ago, between the Secondary or Mesozoic era (Cretaceous period) and the Tertiary or Cenozoic one (Eocene period), massive brains and skilled forelimbs did develop in a group of mammals from which came both monkeys and man.
The primates were animals missing of particular specializations, but which received from the evolution rather big brains, pentadactylous and prehensile hands and feet and an acute vision and tactile sensibility. The eyes were placed in front, thus allowing a stereoscopic vision and acquired the capacity to perceive the colours.
The fingertips, very sensitive, were reinforced by flat or tegular nails; the thumb or the big toe separated from the other fingers, becoming more or less opponent and developed, granting in this way a good prehensile capacity to the hand and the foot, absent till then in the other groups of animals present on earth, and this resulted being an essential point in their natural history.
Few primitive characteristics are unluckily conserved in the fossils and the scientists must at times deduce the form and the appearance of old extinct specimens solely through mandibular fragments of few teeth which have remained intact, a real and true policy investigation work.
Those belonging to the oldest primates reveal that these animals nourished of fruits, the dentition later has not assumed particular characteristics, keeping a non specialized structure, typical of the omnivorous alimentation, as is the case nowadays of most of the monkeys.
The first fossil teeth of primates date from the late Cretaceous period, about 70 millions of years ago.
During the Eocene (54-38 millions of years ago), there was a great radiative expansion of all mammals and the first properly called families of Primates came to life.
Between them, the most important were the family of the Adapids (Adapidae), that of the Tarsids (Tarsiidae) and the one of the Omomyids (Omomyidae).
The adapids, with their elongated muzzle, were perhaps the predecessors of the present Lemurids (Lemuridae) and the Loris (Lorisidae or Loridae).
After some biologists, the Smilodectes should have been the first lemurids, which lived by the early Eocene. It had the eyes still placed on the sides and hands, capable to grasp the objects, with which it was able to climb the trees.
The tarsids, with a broad muzzle and primitive teeth, were the predecessors of the present tarsiers; the Necrolemur, was one of them. It had a stereoscopic vision which permitted to evaluate the distances and to jump from a branch to another.
The omomyds probably originated the most elevated forms of primates, the Anthropoidea, which include the anthropomorphic apes and man.
The distribution of the fossil skeletons, indicates the existence in the past of a bridge (isthmus) between Eurasia and North America, which ceased to exist by the end of the Eocene period: 38 millions of years ago.
This at the time when the continental shelves parted by means of the continental drift because of the movements of the tectonic plates, still under way, has allowed the evolutionary development of two huge groups of apes, the anthropoid of the Old World and the primates of the New one.
The anthropoids of the Old World prevailed at once, through ecological competition, on the Adapids (Adapidae) and on the Tarsids ( Tarsiidae), which were able to survive till now only by adopting nocturnal customs and habits.
But in the New World all North American primates extinguished almost at the same time, leaving as survivors only the Omomyds (Omomyidae), coming from the North, whose evolution brought to the present monkeys of the New World, the Platyrrhines (Platyrrhini).
The oldest anthropoids of the Old World, the Catarrhines (Catarrhini, from the old Greek: narrow nose), included animals already close to the anthropomorphous, which were going on all fours. The first fossils anthropomorphouses, represented by the Aegyptopithecus, date from the end of the Oligocene, 30 millions of years ago.
By mid Miocene, that is about 20-15 millions of years ago, did live in eastern Africa forms of primates like the Proconsul, possible ancestor of the gorilla and the chimpanzee, belonging to the family of the Pongids (Pongidae), primitive anthropoid, which, after some authors, has generated all present anthropomorphic monkeys.
Another member of the Pongidae, present at the same time in eastern Africa, was the Pliopithecus a smart jumper, more slender than the Proconsul, had teeth similar to those of the gibbon (a member of the family of the Hylobatidae), but with long limbs and tails, sign that it was a runner and a jumper, contrarily to the gibbon which is an arboreal animal par excellence.
The Victoriapithecus , on the contrary, should have originated a group of Loris (family: Lorisidae), ancestors of the present galagos (superfamily: Lorisoidea, family: Galagidae) and the potto (genus: Perodicticus) and to the family of the Cercopitechidae of which a primitive member, ancestor of the Langur, was the Mesopithecus, about 50 cm long, four-handed, which lived in the Pliocene period, recent era, about 1-2 millions of years ago and had a strong resemblance with the present Langurs (genus: Semnopithecus), endemic to southern Asia.
Order of the Primates, classification
The short evolutionary history I have traced for the primates, obviously incomplete for many primatologists, is however sufficient for our purpose, which is to talk in a more detailed way of the prosimians, anthropoid apes and monkeys which form along with the hominids the order of the Primates, seeing their present classification and the characteristics (morphology, ecology, ethology, reproductive biology) of its members.
In this general introduction, we shall consider the best known members of this order, seen the enormous dimensions and the complexity characterizing it. In each text we shall then treat about all the single primates known nowadays to the Biology.
I would like to pinpoint that the description I will do about these members in this general part, will be based on my personal formation as zoologist-ecologist biologist, rather than as physic anthropologist or primatologist, which means to consider the ecosystems-biotopes were the primates are, because it is a characteristic unifying them, as most of them, independently if they have a mainly arboreal or mixed life (arboreal-terrestrial), are in any case present in great number inside the tropical-pluvial evergreen African, Asiatic and Central-Southern American forests.
As briefly previously described, between the compared-anatomic peculiar to the primates, we find that the frontal disposition of the eyes (which are also in condition to perceive the colours in the spectre of the visible), has allowed the acquisition of a stereoscopic sight (which permits to look into the depth, evaluating the distances, for instance from a branch to another), which, along with the formation of opposing thumbs, therefore of a prehensile grasp, have granted them the development of the arboreal life, typical of many primates and anthropoids.
Arboreal life means brachiation, phenomenon so much developed and utilized for instance by the gibbons, which consists in moving on the trees, without never getting in contact with the ground, from a branch to another, utilizing the fore limbs and the prehensile grasp, with the same facility we have for walking.
In doing this are very able, apart the aforementioned gibbon, also the orang-utan, the chimpanzee and the ceboid, which, any way, can also stay on the ground. The same thing happens for the Gorilla (Gorilla gorilla).
But it is indispensable to establish at once that the anthropomorphic apes, that is the most evolved, such as the Orang-utan (Pongo pygmaeus), the Chimpanzee (Pan troglodytes) and the Gorilla (Gorilla gorilla), are not capable to walk erect in a continuous way, but only for short tracts, usually they are four-handed, that is they move on the four limbs, but they can stop for a while in erect position.
In reality, between the three aforementioned anthropomorphic species, the Chimpanzee (Pan troglodytes), together with the anthropoid Ceboid (from the old Greek Kébos: long-tailed monkey, infraorder: Platyrrhini, family: Cebidae, subfamily: Cebinae, genus: Cebus) and the anthropomorphic Bonobo also called Dwarf or Pygmy Chimpanzee (Pan paniscus), is considered by the primatologists to stand between the most intelligent apes, by sure the one with the best ambulation on the ground; for what the intelligence is concerned, it is then difficult (at least this looks to me) to establish who is more or less intelligent, if it is still not yet clear what is meant for intelligence on the biologic point of view.
Other characteristics in the primates are the pentadactyly, the absence of claws, replaced by nails (with a shape which can be flat, tegular in the anthropomorphic, long and bent mainly in the less evolved primates, prosimians).
But man as primate, who is cosmopolitan, most of the primates are located in the tropical and subtropical regions.
The present classification of the order of the Primates considers them as subdivided in two suborders.
Suborder of the Prosimii (prosimians)
It gathers the most primitive primates; they have a long muzzle and the eyes not always frontally placed. It is subdivided in six families:
Tupaiidae (Tupaias: 20 species). At times, in the past, classified between the insectivores, the tupaias look like squirrels with a long muzzle. The scrotum, unlike the other primates, is placed in front of the penis. They have long and agile fingers, with sharp nails and little bent. They all live in the tropical forests of Asia. An example is the species Tupaia of the Philippines (Urogale everetti,) living only in the Mindanao Island, the second largest of the Philippines.
Lemuridae (Lemurs: 15 species). They are the typical primates of Madagascar. Their lower incisors, unlike those of the tupaias, form a sort of a comb, utilized for grooming. All fingers are provided with nails, but on each second toe there is a claw, also utilized for grooming. The thumb and the big toe can oppose to the other fingers. For instance, the Ruffed Lemur (Varecia variegata), lives in North-eastern Madagascar. It has a long-haired ruff around the neck and the sides of the body. There are three races with different colours. The Gray Mouse Lemur (Microcebus murinus) is 12 cm long and the tail is 16 cm long; it lives in the forests of western Madagascar; in the whole it looks like a dormouse. These lemurs are the smallest primates; agile and nocturnal, they eat insects. It looks possible that they are similar to the bushbabies of Africa.
Indriidae (Indri and Sifaka: 4 species). The members of this family, are similar to the lemurids, as they climb moving one hand over the other, they cling to the vertical branches in erect position and move bouncing on the ground being their legs longer than the arms. They are frugivorous-vegetarian animals, as they nourish of fruits and leaves. Examples are the Indri (Indri indri), living only in eastern Madagascar forests. Active during the day, it emits a gloomy and mournful cry.
Daubentoniidae (one species only). Aye-aye (Daubentonia madagascariensis), lives in northern Madagascar. Like rodents, it has only one incisor on each side of the jaw and with it makes holes in the bark, after having taped it with the long fingers, with an average of eight times per second. This permits to establish, varying the sound density and utilizing the very sensitive hearing, where are located the big larvae of insect, a coleopteran, for instance, which reaches then with its flexible middle finger for eating it.
Lorisidae (lorises, pottos and galagos: 11 species). The lorises and the pottos have slow movements, so that they can catch the birds by surprise. Their hands and feet are specialized for grasping; the first finger is opposable and very robust. The galagos have a long tail, big eyes and showy and mobile ears. They cling to the branches vertically and hop on the hind limbs when on the ground. They are all nocturnal; like the lemurids, they have a dental comb. An example is the Red Slender Loris (Loris tardigradus), lives in southern India and in Ceylon; it is a slender animal and tailless.
Tarsiidae (Tarsiers: 3 species). They have flat face, very big eyes, roundish skull and do not have a dental comb. The ocular bulbs are so big that they cannot rotate and move inside the orbit where they are lodged, assuming, like in the Tarsius spectrum, a fixed position. The head, which can rotate even of 180 degrees, and the big ears, assume the role the mobile eyes have in the other animals, permitting to sight the arrival of a predator or the presence of a prey. The legs are long, especially the tarsi; the lower part of the tail, bare and scaly, serves as support. Tarsiers are active only by night, when they jump from a trunk to another. They live in South-eastern Asia. An example is the aforementioned Spectral Tarsier (Tarsius spectrum) living in the jungle bush of Celebes and the nearby islands.
This includes the most evolved primates, with short muzzle and a complete stereoscopic vision. It subdivides in two infraorders which perhaps have evolved independently from the previous prosimians: the Platyrrhines (Platyrrhini), with two families and the Catarrhines (Catarrhini) with three families.
The platyrrhines, with much spaced nostrils, facing sides, live only in South America, whilst the catarrhines, with closer nostrils and facedown, are located in Africa and Asia. The two families of the Platyrrhines are:
Callitrichidae (Marmosets and lion tarmasins: 21 species). These small monkeys, have clawed tails on all fingers but the big toe; they do not utilize the tail for clinging. They all have diurnal habits. Examples are the Goeldi’s Marmoset (Callimico goeldii), 21 cm long, with a tail of 31 cm; it lives in the Upper Amazonia. It is black, with a hood of long hair. Other example is the Common Marmoset (Callithrix jacchus) living in the tropical and subtropical Brazilian and Bolivian forests.
Cebidae (Cebids: 26 species). These monkeys, with nails on all fingers, are bigger than the callitrichids and their movements are less jumping. Some species have a prehensile tail. Examples are, Douroucoulis or Night Monkey (Aotus trivirgatus), 45 cm long and a tail of 40 cm; is the only anthropoid primate having nocturnal habits. It lives in the forests, from Nicaragua to Argentina and from Guyana to Peru up to Ecuador. It has big eyes, similar to the owl, surrounded by white. Another odd example is the so-called Spider Monkey (Ateles paniscus), living in the tropical forests from southern Mexico to Brazil. It has long limbs and while moving utilizes the tail like a fifth limb.
The three families of the Catarrhines are:
Cercopithecidae (Old World Monkeys: 60 species). They walk crawling and have a certain gesture. The family includes two different groups: the colobines, with a complex stomach, apt for digesting the leaves, and the cercopithecines, omnivorous, which have a simple stomach and ample cheeky poaches where they can store the food. Examples are the Guereza (Colobus polykomos), 60 cm long and with a tail of 90 cm; it lives in the central areas of the African forest. It has a black coat, with white zones. A second example is the Langur or Entellus (Presbytis entellus), is spread in the forests of India and Pakistan; it has a thick and silky hair. Unlike the other species of the same genus, it mostly lives on the ground.
The Grivet (Cercopithecus aethiops) is 80 cm long, with a tail of 60 cm, lives in the woody savannah African regions.
The Diademed Monkey (Cercopithecus mitis) prefers the trees close to the water courses. The male is bigger than the female and can reach the 70 cm, with a metre long tail.
The Drill (Mandrillus leucophaeus) is 70 cm long, with a tail of 12,5 cm, lives in the African equatorial forests, has a black muzzle with raised grooves on the nose and red and blue buttocks.
The Gelada (Theropithecus gelada) is 72,5 cm long, with a tail of about 50 cm, lives in the Ethiopian plateau. It has a red patch of bare skin on the chest, a tail ending in a tuft and strong mandibles with much developed canines, long even 6-7 cm. The male, as mark of sexual dimorphism, has a mane, which, with the age, gets grey-silver tones.
Finally, another classical example is the Rhesus (Macaca mulatta). This monkey is located in northern India, southern China and in Indochina. The factor Rh (the presence of which is indicated with Rh+ and the absence of Rh-) is a determining antigenic which together with the A, B, O, is utilized in medicine for determining the human blood groups. It was isolated in the fifties by the American biologist R. Lewis, in these monkeys.
Pongidae (anthropomorphic monkeys: 9 species). Tailless, they have long and robust arms; the cranial box is big, with inside a much developed brain. Like for the human brain, the cerebral cortex is observable. These monkeys are the most similar to man animals.
Examples are: the Gibbon (Hylobates lar), living in Burma, Thailand, Malacca, Borneo, Sumatra and Java forests. Slender and agile, it stays almost always on the trees, from where it hangs with its long arms and swings from branch to branch, brachiation; when on the ground, it can walk erect for short tracts. These apes live in couples and emit deep and strong territorial calls which can be heard even at 3 km of distance.
Then, we have the Orang-utan (Pongo pygmaeus), which, when standing, can be 1,65 m tall; it lives in the forests of Borneo and northern Sumatra. It has sparse, dishevelled and reddish hair; hand and feet look similar. The male has a huge cutaneous sack, similar to a goiter, with which it amplifies the cries and two adipose protuberances on the cheeks.
The Chimpanzee (Pan troglodytes) is about 1,05 m tall, lives in the African tropical forests and is more spread than the gorilla. It has ears with a great pinna, the hair is black and long.
It lives both on the trees and on the ground, in rather free communities, without an established leader, its worst foe is the Leopard (Panthera pardus).
Finally, the Gorilla (Gorilla gorilla), which, erect, reaches even the 2 m of height; it lives in the equatorial forests of tropical Africa.
Biologists think, convinced, that the gorilla together with the chimpanzee stands between the apes more akin to man.
It is the one, between the primates, reaching the maximum dimensions. The limbs have morphometric proportions more human than those of the orang-utan, even if always longer than the legs. The feet are similar to the hands, with the big toe bigger than the other toes.
Usually, gorillas crawl; they are completely terrestrial.
They are quieter and more reserved than the chimpanzees; they have short, thick and black hair.
They live in groups of even 30 individuals, having an adult dominating male as leader; this has usually the grey back, from which the name of Silver back.
Hominidae (one species only). Man (Homo sapiens sapiens). Cosmopolitan, thanks to his ability to adapt (at times even too much) the habitat to his exigencies.
This family has evolved from an anthropoid progenitor common with the anthropomorphic monkeys, about 26 millions of years ago; but the present man has appeared only about 40.000 years ago.
They distinguish from the other primates for a very developed brain, for which he can utilize a complex verbal language, for the erect standing, with which can walk and run, implying a particular skeletal and spinal structure, apart adequate skeletal striated muscles, and for the sparse hairs on the body.
Asia tropical forests
After the above discussed short classification, we begin now to study the different types of primates, setting the speech in zoo-ecologic terms, that is, moving around in the ecosystems-biotopes where they live.
Inside the Asiatic pluvial-tropical forests, we find a rather wide spectrum of primates, from the less evolved to the anthropomorphs.
Between the less advanced, we have the tarsiers, the loris and the treeshrews.
These monkeys, are unchanged since 70 millions of years ago, that is from the Secondary or Mesozoic, Cretaceous period.
The treeshrews, or animals very much alike, did exist on the earth already 70 millions of years ago. In this big space of time, these small placentate mammals (some of them are only 15-20 cm long and the tail has the same length), have changed very little.
Like their ancestors, the extant species live in the forests and like them have an elongated muzzle, small ears and tails usually longer than the whole body.
There are several extant species of treeshrews, very similar in their appearance, almost all with brown or olivaceous hair.
On the contrary, the ethological characteristics and the character differ very much between the species: some are solitary and aggressive, like the Common Treeshrews (Tupaia glis); in fact, when they live in captivity or in a controlled habitat (zoological garden), if two males face each other, they fight ferociously, often until death.
The males, in the wild and in captivity, mark the territory with faeces, urine and with a very strong odorous secretion, emitted rubbing a ventral gland.
The female of these animals prepares the nest after having marked the territory with vaginal secretions, in order to attract a partner, during the oestrum, for coupling. It gives birth to a cub after a gestation of 50 days (as almost all primates are monovular species, even if they can, rarely and less frequently than in humans, get cases of bigeminy or of polygeminy, therefore with birth of twins). At this point, the male goes to live elsewhere.
On the contrary the Mountain Treeshrew (Tupaia montana) is a very quiet and friendly species.
These uncommon animals of the high mountains of northern Borneo, live in small groups of 8-10 individuals, each one comprising more males which tolerate each other. The females in oestrum are polygamous and mate even with two or three males at the same time.
The Tupaia longipes lives in polygamous familiar groups, formed by a male, the leader, and by several females living in harmony, cooperating in the research of food or in smoothing the hair with the teeth.
When a female is pregnant, it prepares the nest and the companions ally for keeping the male far away at the moment of the delivery, as it might kill or cause harm to the just born cub.
In the common treeshrews, on the contrary, where males and females can live solitary or in couple, after the delivery the cub is nursed by the mother every 48 hours, giving however a quantity of milk equal in volume to the 3/5 of its body volume.
Between the meals, it abandons the cub and sleeps with the male in another nest.
The cub, born bare and blind, becomes autonomous when about one month old.
Most of the species of treeshrews live on the trees; but there are some living on the soil and nidifying in dens of hollows of the same, such as the Large Treeshrew (Tupaia tana) and the Mindanao Treeshrew (Urogale everetti) of the Philippines.
The terrestrial treeshrews look like the Tupaia longipes, for what the social hierarchy in the families is concerned, but not for the solidarity between females, which ally only for defending the cubs from the adult males.
All treeshrews are active during the day, have elongated muzzles and lateral eyes, characters which in reality are not found any more even starting from other inferior primates. In any case, they are close to the primates for what the development of the brain is concerned, the arboreal habits and the absence of specialized morphologic structures, related to activities such as swimming, flying or digging.
Their zoogeography tells us that the genus Tupaia is the most spread of the five genera concerning the family of the Tupaiidae , endemic to south-eastern Asia.
The species of the genus Tupaia are a dozen, the others genera of Tupaiidae have only one species each, for a total of 20 species.
Finally, for the treeshrews it is interesting to consider a species, the Tupaia belangeri, as this was studied, in wild and in controlled (zoological garden) regimen by the German biologist D.V. Holst during the early sixties.
The author intended to observe, in the two aforementioned conditions, the phenomenon of the stress caused by an increase of the population density on the physiology (auto-ecology) of the animal and in terms of synecologycal response (response of community).
It was observed, in those years, that the animal populations avoid carefully and with much elegance the overpopulation without awaiting, for instance, the famines which would cause inter-specific phenomena of competition so violent to generate cannibalism and infanticide.
These studies made by the biologists had also the purpose to explain some aberrant phenomena of mass which happen in the human being, through a socio-biologic approach.
They were observing that in several species of murines, of lagomorphs and of deer (like the Japanese Deer, Cervus nippon), as well as in the marmots and also in the microti (parasite protozoan, like the Babesia microti), the uncontrolled increase of the demographic density was causing a sequence of stressors, so much to induce harms to the single individuals and to interrupt the growth of the population.
In the vertebrates, in particular in mammals, were observed two fundamental systems called “of harmonic retroaction”, acting on the dynamics of the population: one reduces and hinders the reproduction, and the second which reduces the resistance to the infections and parasitic pests, thus increasing the death rate. The aim is the same: to prevent the demographic crises when the biotic potential (reproductive) exceeds the available alimentary resources in a certain vital area.
The two systems were so classified:
The adrenocorticotropic system (ACTH) – hormone of the adrenal cortex – which, when in presence of a disturbing factor (stressor) as well as of an excessive demographic growth, activates beyond the physiologic level, increasing the mortality as the predisposition to the infections and the parasitic infestations increases and the production of antibody reduces. The excessive production of ACTH causes also glomerulonephritis and therefore a real nephropathy. More, the function of the adenohypophysis (front portion of the hypophysis – or pituitary gland – gland appendix of the diencephalon) disappears followed by metabolic damages: the growth is delayed, there is decrease in body weight, etc.
The second hormonal system is the gonadotrope – hormones stimulating the activity of the sexual organs. When it reduces its functions, there is denatality, and ion the case there is progeny, the newborns cannot be bred normally, as the lactation is not sufficient. Frequently the parents eat their sons and by the end, under these conditions, only the most capable and strongest survives.
In the case of the Tupaia belangeri, Holst has studied the phenomenon inside the parental communities, in the wild and in controlled habitat.
In these primates, the social stress can be measured quantitatively according to the rising (phenomenon of the horripilation) of the hair of the tail (the Erectores pili operate through the orthosympathetic component of the autonomic nervous system). In the case of perturbations, stressors, like an aggression made by a member of the same species, in the running away, in frightening situations and in instances of overcrowding with the fellows of the community, the hair of the tail remain risen for a more or less time.
When a dominant of the group meets the recessive, it will be this last one to raise the hair, the dominant will do it only is attacked.
Calculating the percentage of rising time of the hair, during observation sessions lasting twelve hours, the author has reached the following conclusions:
The females of Tupaia belangeri which have raised the hair of their tail for more than the 20% of the time during the observations session, were trying to mate with other con-specifics both males and females, aberrant sexual behaviour, due to a wrong hormonal title. The cubs of these females, are eaten during the first two days of post-natal life, either if they are the own ones or those of another female. If the social stressors are so much strong that the hair of the tail keeps risen for more than the 50% of the observation session, the females become completely sterile. This is caused by the degeneration of the ovarian follicles which are ripening in the ovaries.
In the males, the spermatogenesis stops if the rising of the hair is more than the 70% of the observation time (psychic castration). The higher the frequency with which the hairs of the tail are risen, the greater is the loss in weight of the animals, the cubs grow up more slowly; the number of the leukocytes in the case of rising over the 20% increases in 1-2 days from about 3000 to 6000 (in 8000 cubic mm of blood); for frequencies around the 90% the animals pass away after 8-14 days, even if the food is abundant and there are no fights.
This experiment evidences how such phenomena are complex, and it has been noted a similarity of responses in the human being.
The systematic position of the tupaias is controversial, not all zoologists admit them between the primates. Every doubt disappears when it is matter of the other five families of prosimians living in the tropical zones.
These animals, represented in the Asiatic tropical forests by the tarsiers and by the lorises, in fact, they show better than the tupaias the characters of the primates.
The hands, provided with nails and not claws, are better apt for grasping; the eyes placed in the frontal part of the skull, ensure the binocular sight, permitting to evaluate the distances and therefore to be able to escape a predator, or to run after a prey. The front legs of the tupaias, long and flexible, are equipped with claws, very skilful in grabbing a prey. The tarsiers, on the contrary, have hands with long fingers ending with discoidal expansions, which increase the contact surface.
The tarsier is a powerful jumper; long only 10-15 cm, it can perform jumps from a branch to another of even 2 m. Before falling on the branch, it lashes the air with the tail, which acts as a brake. The disks of the fingers can adhere to whatever type of surface. The frontal eyes permit a precise calculation of the distances.
Even if deeply asleep, the tarsiers cling to the trees, keeping vertical thanks to the adhesive disks of the fingers. Another support is provided by the rough and scaly tail, which is lying on the trunk. It seems that this is the way these primates have for resting as they do not seem to nidify.
As the enormous eyes remain steady and fix in the orbits, in order to survey the possible presence close to them of predators and preys, the tarsiers can rotate the head of 180°.
They eat insects and larvae, but they do not disdain lizards, small birds or mice, which they can chop with their hands.
Between the various tarsiers, we find the Spectral Tarsier (Tarsius spectrum), the Philippine Tarsier (Tarsius syrichta), the Horsfield’s Tarsier (Tarsius bancanus), all endemic to South-eastern Asia; the fact of living in islands where they do not have to compete with more evolved species has granted them the survival.
Between all the prosimians, they are those closer to the monkeys.
The lorises, similar to the pottos and to the African bushbabies, move slowly and silently, which represents perhaps an ecologic adaptation for hunting small vertebrates, like birds, rodents, reptilians or also arthropods and insects, which they chase noiselessly and kill, once caught, holding them tightly between the two hands.
In the slow loris, a Loridae, the reduced forefinger of the hands increases the opening of the same, thus allowing a firm grasp of the branches and of the preys.
All lorises cling to the branches with hands and feet, remaining there even for a long time, without getting tired.
In other mammals, usually, the contraction of the muscles constricts the veins and slows down the circulation; in the lorises, on the contrary, the calibre keeps constant in these situations and the toxins go on in being regularly eliminated by the blood through the kidneys.
The Slender Loris (Loris tardigradus), only 30 cm long, has an ample diffusion in the forests of southern India and Ceylon.
The Slender Lorises weigh about two hectograms; reproduce twice a year and the gestation lasts five months and a half.
To the family of the Loridae belong also the slow lorises such as the Kukang (Nycticebus coucang) and the Pygmy Slow Loris (Nycticebus pygmaeus), endemic to South-eastern Asia.
They are more robust than the lorises and have a dark strip along the back and dark rings around the eyes.
All these animals live alone or form transitory couples.
The slow loris spends almost all the time on the trees and rarely comes down to the soil. During the day, it sleeps either crouched on a branch or hidden inside a hollow tree. During the night it hunts small mammals, insects and eats also fruits.
Grasping with the hands and the feet, it moves slowly and carefully, from branch to branch and remains at times hanging suspended upside down while eating. It’s only 25-35 cm long.
But, as we said at the beginning of this paragraph, in the Asiatic pluvial-tropical forests does live also a wide choice of monkeys, more or less evolved.
Therefore, beyond the prosimians just described, which are always primates, there are also true and real monkeys.
Almost all the monkeys of the Asiatic forests live in social groups very united and sorted in precise hierarchies, but with a life which is often disturbed by fights for the predominance.
The Macaques (genus: Macaca) and the Semnopithecuses (genus: Semnopithecus) are the two genera of monkey, autochthonous of the Asiatic forests, belonging to the family of the Cercopithecidae.
The macaques are aggressive and cantankerous, eat everything and live on the ground or in the lower layers of the forest.
The semnopithecuses, which eat leaves, are less aggressive and live preferably in the higher levels in the forest. In case of cohabitation of the two species, the semnopithecuses live on top of the trees, the macaques live below.
The overlapping of the ranges is guaranteed by the fact that the two genera have two different types of alimentary ecology characterizing them, and so they are not competitors.
The robust macaques of these forests tend to live in vast social groups where are present both sexes and all ages.
One of the most known is the Rhesus Macaque or, simply, the Rhesus (Macaca rhesus) living in groups organized socially including 10 to 30 individuals, dominated by two or more males. When a female is in heat normally couples with one of the leaders, then the two begin to live together, looking for food together, smooth the hair and clean up each other. This habit represents a dynamics of socialization obtained by touch, sense which is very developed in the monkeys.
The groups live in territories overlapping at times; a hierarchy between them is then established with real and true ranks and the subordinate band must leave the place when the dominant ones arrive. If this doesn’t happen, a fight will arise.
How much of human can we see in all this?
We have to think to the famous movie of Martin Scorsese “Gangs of New York” where the various gangs of Irish, Italians, Portuguese, Jewish, Germans, Polish, were conquering with fights, the different parts of the forming New York, during the second half of the nineteenth century.
In southern India, the Macaca rhesus is replaced by the Bonnet Macaque (Macaca radiata) and, in Ceylon, this is replaced by the Toque Macaque (Macaca sinica).
All are red-faced monkeys, with a sort of circular bonnet on the head made by long hairs.
Usually the ranges of the different species of macaques living on the ground do not overlap as each species occupies a different region. In the case of the Macaca rhesus, this lives in the woody savannahs and also in the thick forests.
In South-East Asia and in Indonesia, the most common species is the Crab-eating Macaque (Macaca fascicularis), a monkey with a slender body and long tail, which lives in big bands (up to 70 individuals, even if as an average they are about twenty), where are two or three females per each male. The bands remain almost all the time on the trees and rarely close bands scuffle between them. The woody zones they colonize are those close to the sea line and the rivers, avoiding the mountain ones, jumping from a tree to another between the trees. They eat fruits, leaves, seeds, insects, small reptilians and crabs, from which the name.
The dominant males join for better protecting the groups and, when a predator, like a Leopard (Panthera pardus) or a Tiger (Panthera tigris) is present, they emit loud cries of alarm and escape.
The Southern Pig-tailed Macaque (Macaca nemestrina) of Burma, Malaysia and Borneo has, on the contrary, a short tail of only 15-20 cm.
This species lives on the ground or on the lowest branches, in groups varying from 30 to 50 individuals. It is close to the rare Lion-tailed Macaque (Macaca silenus), living in the mountain forests of south-eastern India. For moving, it never jumps from a tree to another, but gets down from a tree to the ground, for then climbing the next one. The lion-tailed macaque, called also Wandura, or white-bearded monkey, is one of the most beautiful species of macaques due to its white and black hair; but if it enters the coconut plantations it can cause considerable damages.
In the South of China we find the Macaca arctoides, with a shorter tail than the previous species, and measuring only 10 cm.
In Celebes Island there are approximately other six species, between them the Crested Black Macaque (Macaca nigra), whilst in Japan we have the famous Japanese Macaque or Red-faced (Macaca fuscata).
These last macaques, have a hierarchical structure, as it was observed by the DrSc J. Itani, Japanese biologist who studied them for 30 years, where the female-male ratio is of 3 to 1.
They are much intelligent; they have learnt, for instance, how to look under the stones of the rivers for the presence of shrimps, crabs and molluscs, of which they nourish.
Furthermore, during the rigid Japanese winters, where their physiology allows them to survive, they take advantage of the characteristics of Japan, which is a volcanic archipelago, where are ponds and water sources close to volcanic systems with pleasantly warm water, with temperatures of 30° C higher than the surroundings.
Unluckily, only those having a higher position in the band can utilize them, cubs included, and so once more we can note typical and negative human-like characteristics, such as selfishness and oppression.
The gestation of the females last about 173 days and they deliver one cub only weighing about 500 grams; the lifespan is of about 30 years.
The Semnopithecus, called also leaves eaters monkeys, are more agile than the macaques and mostly do live almost always on the trees. They nourish basically of leaves and have a specialized stomach with three sacs, in one of which the leaves, finely chewed, are digested by the bacterial flora.
Unlike the omnivorous monkeys (i.e. macaques and baboons) they do not have cheek poaches where to store the food.
The Entellus or Langur (Presbytis entellus), perhaps the species most known of this group, spends, on the contrary, most of its day on the ground and then goes back on the trees for the night. It lives in groups composed by 15 to 30 individuals and the ranges often do overlap.
The groups do not show a marked antagonism when they meet. They have a hierarchical organization in the band, but not so marked as in the macaques.
When the are quarrels inside a group, the leader does not intervene as it happens, on the contrary, for the macaques; but anyway, like does its colleague in the macaques, it bites a subordinate for sending it away, whilst, for just leaving it go, it puts a hand on the shoulder.
The males of this species do not court the females, but it’s these last, when in heat, come to the males showing them their anus.
The female has single deliveries; the cub spends most of the first time of its infancy clinging to the mother’s belly.
In the dry areas of India, the entellus has a very singular behaviour: the groups of female and young of both sexes are lead by an adult male. The remaining males, form another group and at times they are able to send away, with real rebellions the dominant male of the mixed group.
This means that the males fight between them, the winner kills or tries to kill the cubs of the group being nursed, when the nursing ceases, it synchronizes ex novo the oestrum cycle of the females, which become again receptive for coupling.
This for the biologists, when discovered, was a surprise (thing that in the felines, like the solitary lions in quest of female is on the contrary rather frequent) because it is clearly contrasting with the affectionate care that normally have the males towards the young monkeys.
In some bands of langurs of the Nilghiri Mountains, there is only one adult male, which at times chases the females and the young of the rivalling bands; these react with the same cry with which they signal the appearance of a bird of prey.
Beyond the entellus-langur, do belong to the Semnopithecus also the proboscis monkeys with the two species of the genus Nasalis , the Nasalis larvatus and the Nasalis concolor both discovered in 1787 by the German biologist Wurmb.
The proboscis monkeys live in marshy forests and they climb the trees for the night. Every band wanders in areas of about one square km jumping or crossing the water streams. In the male the nose becomes always bigger and longer with the age and erects when the animal, frightened, emits its strong cry of alarm. It is absent in the female, it is therefore a character of sexual dimorphism.
The proboscis monkey is close to the langur or entellus.
Other species of langur or entellus, beyond the Presbytis entellus, endemic to south-eastern Asia are the Presbytis senex, Presbytis johoni, Presbytis pileatus, Presbytis cristatus, Presbytis nemaeus .
During about twenty years, Indian biologists, in collaboration with English ones, have studied several communities of Langur (Presbytis entellus) on the field, describing their gestures and screams, showing that both change with the age and indicating that it does exist, during the physical and sexual development of the animals, an ontogenetic maturation of biologic and psychic activities which describe, according to the emitter, the stage of maturity and the position it holds inside its group.
This project has permitted the biologists to categorize the various vocal emissions and the various gestures, by which it has been possible to prepare a scheme correlating the biologic development with the psychic one, determining the variation of behaviour depending on the age.
Infant 1: from birth to 3-5 months. The coat, in both sexes, changes from brown to grey.
Infant 2: From when the coat does not change of colour any more (3-5 months), to the weaning (12-15 months).
Young: from 15 months to 3 years for the females, to 4 years for males.
Subadult: from 3 years to the sexual maturity, that is 4 years for the females; from 4 years to sexual maturity, that is 6-7 years for the males.
Adult: From the birth of the first son to about 4 years for the females; from the complete muscular development, to 6-7 years for the males.
These biologic categories were correlated to specific phenomena of gestures and sounds, which were part of two psychic categories.
The Bornean Orang-utans (Pongo pygmaeus) and the Lar Gibbons (Hylobates lar) represent the two species of anthropomorphic apes living in the Asiatic pluvial-tropical jungles. Both are very agile on the trees, taking advantage from the brachiation, but awkward on the ground.
The four genera of anthropomorphic apes, Chimpanzee (Pan troglodytes), Gorilla (Gorilla gorilla), Orang-utan (Pongo pygmaeus) and Lar Gibbon (Hylobates lar), where the first two even if endemic to the same biotope, tropical forest, are in a different zoogeographic area, Africa (and after the biologists they are those closer per affinity to the Homo sapiens sapiens) have remarkable common characteristics.
We briefly remind that between the genome of Homo sapiens sapiens and of Pan troglodytes there is the 99% of coincidence!
All have a very ample cranial box, containing a very developed brain, characterized (like the human one) by an evident cerebral cortex.
They have low frontal nostrils, big orbital cavities, very developed pinnae, pentadactyl hands and feet with fingers/toes with flat or tegular nails, muscular mass very developed both in the four limbs and on the back, dentition not specialized, indication of an omnivorous alimentary regimen, arms longer than the legs, opposition of thumb-forefinger, with more or less developed thumb, in order to ensure a prehensile grasp.
They have manual aptitudes, indication of an adequate psychic development, frontal eyes, binocular vision, colour perception, absence of tail.
Finally, they can all assume the bipedal posture, but the one feeling better in this is the chimpanzee. All four can walk erect for short distances, but the preferred de-ambulation remains anyway that on the four limbs. The orang-utan, for instance, leans on the lateral sides of the palms.
Both Asiatic anthropomorphs prefer to be arboreal, even if they can come down to the ground for short periods, mainly during the explorative phases.
The gibbons swing between the branches, hanging with the long arms and jumping from tree to tree.
The orang-utans swing considerably less, never jump, but thanks to their flexible feet, they climb easily on the trunks of the trees.
We must remind that hands and feet in these antropomorphs are equivalent, and this is one of the possible causes of the de-ambulatory difficulty in erect position.
The Orang-utan (Pongo pygmaeus), whose name in Malay means “man of the woods”, due to its resemblance to man when seen from far away, is one of the anthropomorphic apes which arouse more tenderness, with its sociality and its always sad eyes.
The zoologist biologists hypothesize that its ancestors have detached from the main evolution line of the antropomorphs before the Gorilla (Gorilla gorilla) and the Chimpanzee (Pan troglodytes), but after the Lar Gibbon (Hylobates lar). After other zoologists, on the contrary, it is to be considered as a gigantic relative of the gibbons.
The orang-utan males weigh 100 kg and can reach, erect, the 1,65 m of height; the females reach 1,20-1,30 m and weigh about half.
In both sexes, the arms are long one and a half time the legs, hand and feet are similar and long, with flexible and curved fingers.
There is only one species of orang-utan, subdivided in two races, the Bornean Orang-utan (Pongo pygmaeus pygmaeus) and the Sumatran Orang-utan (Pongo pygmaeus abelii).
The Sumatran Orang-utan has a long and narrow face, and usually is more slender and taller than the Bornean one. This last distinguishes because has a redder coat and a wider but less hairy face. Nevertheless, the individual appearance varies between specimens, exactly like for humans.
It seems that the orang-utans can communicate with popping sounds, similar to kisses, which they repeat with intervals of few seconds.
Between this sort of kisses, the adults, especially the males, emit a low and two toned sound.
During the night and little before dawn, the males only emit low and prolonged cries which, between the humid mists of the forest, profiting by the phenomenon of the thermal inversion of Frumkin, see description in the Felidae, can propagate up to 3-4 km of distance.
When on the trees, the orang-utans are less agile than the gibbons and, usually, limit to climb. At times, they walk, erect, on the branches, clinging with the feet and holding, with the hands, the upper branches.
They look for food on the thinnest branches of the trees; the preferred fruit is the durian, but they eat also leaves, seeds, rinds and eggs of birds, for instance, Psittaciformes.
In this respect, we have to say, briefly, that the orang-utans are real botanists as they recognize about 200 fruit plants and green which are edible and about one hundred poisonous, which they avoid; the cub, who lives part of its infancy clinging to the belly of the mother, will be then subjected to a real biologic-like training, by the mother who will teach of which plants and fruits to nourish and to which stage of ripeness and which ones to avoid.
The adult females and the young stay together and move in small groups, whilst the adult males tend to remain solitary.
They do not mate in a particular period; the males stay with the females for some days, couple and then abandon them.
The females usually deliver on cub only (rarely two twins), which comes to life after 9 months of gestation. In the anthropomorphs, the deliveries are almost always single, only the monkeys of the New World have always multiple deliveries.
The cub, of almost 1,5 kg of weight, is nursed for about seven months. Then it learns how to walk on the branches, clinging to the hair of the maternal back.
During the research for food, the orang-utan holds with one hand to the tree, with the other, which is free, picks up the fruits it eats.
The features of the face of the newborns have something of human, then, while growing up, the cheeks become folds and flaps which render the face very wide.
Males and females have also laryngeal pouches which, in the male only, through the endocrine control mediated by the testosterone become heavy double chins which are used as a sound-box.
The Lar Gibbon (Hylobates lar), is nicknamed the acrobat of the tropical forests. As already told, it takes the maximum advantage from brachiation; also other monkeys utilize this means of moving, but none with the elegance, the perfection and the velocity of the gibbon.
When on the ground, in erect position, the stretch their arms outwards thus keeping the balance.
Comparing the morphology of the hand of an orang-utan with that of a gibbon, we observe that this last have longer and more mobile thumbs than the orang-utan, as they are necessary for having a stronger grasp for their perfect brachiation.
The gibbon are the smallest anthropomorphs, have heights varying from 35 to 85 cm; they are slender monkeys, lively, with the arms much longer than the legs; very noisy, they begin to cackle and scream as soon as they wake up in the morning.
With these cries they advise of their presence, their rights on the territory or the meteorological change of the weather.
The most spread species is the White-handed Gibbon (Hylobates lar), capable to effect 15 m jumps from a tree to another.
As most of the species of the same genus, it lives in its own territory and forms family groups composed by father, mother and four sons.
Also for them, there is not a precise and fixed time for the mating and the female generates one baby only, almost hairless; for keeping it warm, the mother folds the legs and warms it between the thighs and the belly. The members of a family groom each other and are much united. There is, on the contrary, hostility between the adults of the same sex.
The gibbons live in the medium part of the trees, but often climb on the treetops looking for fruits.
For nourishing, the family at times trespasses the limit of its territory, thus triggering a vocal fight if it meets another family.
The male launches its war cry and the female its great warning formed by a sequence of crescendo screams.
Some gibbons owe their name to their appearance, for instance the Pileated Gibbon (Hylobates pileatus) has on the head a black hood (from the Latin pileus: cap) surrounded by a white ring.
The hoolock or hoolock Gibbon (Hylobates hoolock) gets its name from the typical cry it emits.
The Black Crested Gibbon (Hylobates concolor) can be recognized by its longer nose; it is the most slender gibbon, and that which, on the ground, runs and keeps better the erect posture compared with the others.
Finally, the two species of siamangs, the common Siamang (Hylobates syndactylus) and the dwarf Siamang (Hylobates klosii), have stocky build and are less hairy than the other gibbons.
The common siamang lives in Sumatra and in Malaysia, in the mountain forests, up to 3000 meters and eats fruits, leaves, insects and eggs of birds.
The dwarf or brown siamang is less frequent and can be found only in the marshes of Mentawei island, West to Sumatra.
It is smaller than the common siamang, as the head and the body are 37 cm long, against the 87 of the other species.
The various cries of the siamang are amplified by a great throat sac. The air, inhaled with a kind of dull bang, expands the laryngeal sac then expired through the mouth produce a harsh cry, while the volume of the sacs reduces.
The two sounds alternate rapidly. When it modulates its vocalisms, the siamang is always seated, whilst the other gibbons cry jumping and fuss.
Also a race of gibbon, Hylobates lar agilis, lives in the forests of Sumatra and Malaysia. The 60% of the individuals living in Sumatra are black, the remaining 40% are brown-yellow; in Malaysia the black one are more than the 90%.
African tropical forests
We shall treat now about the numerous genera and species of monkeys at a different evolution level, present in the African tropical forests, later on we shall treat those present in the tropical forests of Madagascar, called also “Malagasy forest”, as they represent one of those cases of animals evolved in a contest of geographic isolation, the island of Madagascar, where for 50 millions of years, several primates like lemurs and other species have freely evolved, without the presence of other competing monkeys.
Finally, we shall treat about a last geographic area, the centre-south America, where, in the great tropical forests, some primates have evolved, called “monkeys of the New World”, due to the particular morphologic characteristics they have and which are not present in the same biotope in Africa and Asia.
About thirty species of monkeys live in the African tropical forests, distributed in all levels, from the tops of the tallest trees to the ground.
These monkeys are subdivided in four great groups: the colobus, the guenons, the mangabeys and the mandrills.
While walking in the African tropical forests, between the endless wonders both vegetal and animal, while looking up, it is possible to see, for short instants, white tufted tails united to snappy and unpredictable bodies of small animals.
These are the colobus monkeys; they live between the trees, in territory with limits which can be perceived only by their owners.
They are very noisy animals, always active; they nourish mostly of leaves; have long limbs suitable for jumping and are the only monkeys of the Old World with hands without thumbs.
The colobus (genere: Colobus) have a complex stomach which permits them to get the maximum sustenance from a diet poor in proteins, composed by leaves.
Depending on the colour of the coat, the colobus divide in three groups: white and black colobus, red colobus and olivaceous ones.
The most known species is the Guereza (Colobus guereza), with white and black coat; it has a thick beard, white and woolly and a huge white tuft at the extremity of the tail.
The guerezas live in groups formed by few individuals, an average of 9-13, and populate the middle layers of the tropical forests from Ethiopia to Tanzania and, to the West, the spread up to Cameroon. Each troop counts usually only one adult male; the others live isolated. When defending the territory, the males produce acute cries, especially by dawn and dusk. The scream, preceded by a violent snort, lasts about one minute and can be heard even 2 km far away.
A guereza female in oestrum is polygamous: it looks for the male in groups where several of them are and mates with more than one of them.
When a cub comes to life, the females of the troop breed it together.
When two groups of guerezas meet, they sit down and observe, snapping their tongues. The male leading the indigenous group, leaps here and there, making noise, at times jumping to the ground from trees placed even at 6 m of height; finally, the two males leading the troops move the head and shake the branches one against the other.
The invading group usually draws back and the intruding dominant male goes back screaming, while the winner runs after it, screaming too.
The Red Colobus (Colobus badius) lives on the tallest trees of the forest, whilst the (Colobus verus), a small monkey not taller than 50 cm, tail excluded, occupies during the day the lower zones, but climbs up to the tops the night, for sleeping or for escaping a predator.
Due to the absence of thumb in the hands, when eating, they hold the leaves between the palm and the fingers.
A race which in the past was considered as a race apart, is the colobus of Zanzibar, then rightly classified as a subspecies. Nowadays it is in risk of extinction; only about 200 specimens remain and is included in the Red List of Endangered Species of the IUCN.
The guenons, but the green(Cercopithecus pygerythrus), which can be found only in the African prairies, are monkeys spread almost everywhere. They live at different levels of the forest, and have a wide range of colours.
One of them, the Cercopithecus ascanius, characterized by a white dot on the nose, lives in the forests of Congo and Uganda, in small family nuclei of 40-50 individuals, when the abundance of food allows this.
They eat in the morning, then they separate in small groups for resting, and by about noontime they form again great groups for effecting in the afternoon a meal more copious.
They eat fruits, leaves, flowers and insects. To the guenons belong also the Allen’s monkeys of the marshy zones and the talapoin, a so much numerous small monkey that, in some areas of Africa, is considered as a pest for the cultivated fields.
Other guenons are the Cercopithecus hamlyni, called also owl-faced monkey, for the shape of its eyes and the type of expression characterizing it, and the Cercopithecus cephus which moves quickly the head on one side, when it intends to emphasize the favourite members in the clan.
A classical Allen’s monkey is, on the contrary, the (Allenopithecus nigroviridis) which lives in the forests of Congo.
Guenons and mangabeys can live even together in mixed groups, it is not rare to observe females of mangabey breeding cubs of guenons or vice-versa.
Some biologists guess that the Talapoin (Mapithecus talapoin), the smallest African monkey, might be a conjunction ring between guenons and mangabeys.
The mangabeys, are very close to baboons, but have a shorter muzzle and a longer tail. They are essentially arboreal and have a social organization similar to that of the guenons.
The Collared Mangabey (Cercocebus torquatus) of equatorial western Africa, lives in groups of 15-25 individuals in the lower levels of the forest or on the ground.
It eats dried fruits and nuts, which it rubs on the branches for breaking the shell if too hard when bitten, symptom of manual and psychic capacities.
Another mangabey, the Cercocebus albigena, instead of sitting squatted on the legs, as most of the monkeys do, sits on the buttocks, with hands and feet always put forward, and keeps on the trees wrapping the tail around the branches.
The red nose and blue cheeks monkeys, as they are commonly called, are represented by the mandrills.
The mandrill lives preferably in the humid forests of the western coastal regions. The male has a bright red muzzle and blue cheeks. These characteristics, which repeat in a red penis, in a blue scrotum and in red and blue buttocks, represent characters both of sexual dimorphism and as species-specific. Furthermore, the males are stronger and taller than the females.
The drill is smaller than the mandrill; the males of this species are 70 cm tall, those of the previous species are about 85 cm. It has a brown-olive hair turning to white around the black muzzle, whilst the cheeks, only in the males, are red.
The drills live more in the interior of the dry forests; the mandrills stay in the outer areas.
The mandrills, in the humid forests as well as in those of the plains west of Congo, live in the bushes and on the ground, in small familiar nuclei. They complete their diet frugivorous-phytophagous, with small animals (insects, arthropods, saurian, amphibians, small rodents and small birds), which they patiently seek on rocks and pieces of dead wood.
The chimpanzee and the gorilla are the two anthropomorphs par excellence in Africa.
The Chimpanzee (Pan troglodytes), together with the Gorilla (Gorilla gorilla), since the second half of the nineteenth century till now were and are still considered by the biologists as the most evolved anthropomorphic monkeys.
Their social habits and manual capacities place the close to man more than any other species of primates.
The chimpanzee can be found in an area of 2.500.000 square km, close to Equator.
All chimpanzee belong to a unique species, and, after some zoologists, to one only race; other zoologist biologists assert, on the contrary, that there are four different races, among which that of the pygmy chimpanzee.
They are endemic to central-western Equatorial Africa, where they can live both in forests and in savannahs and bushes.
The races in which, after some zoologist biologists, the chimpanzee should subdivide are: the West African Chimpanzee (Pan troglodytes verus), the Central Chimpanzee (Pan troglodytes troglodytes), the Western Chimpanzee (Pan troglodytes schweinfurtii), and the Pygmy Chimpanzee (Pan troglodytes paniscus) called also bonobo, living mainly in the forests South of the Congo river.
In relation to height, it is the third tallest anthropomorphic monkey, after the Orang-utan (Pongo pygmaeus) and the Gorilla (Gorilla gorilla). An adult male can weigh 54 kg, one third of the weight of the gorilla and, when in erect position, it can have a height from 1,05 to 1,50 m.
After the human being, the chimpanzee is the smartest to utilize an object as a tool, a stone as an arm, or, for instance a stick to break the beehives.
In the interior of the tropical forests the chimpanzee nourish of ripen fruits, and, if these are scarce, of leaves. At times they chew for several minutes juicy barks and then spit them.
The chimpanzee living in the shrubby savannah (being, together with the gorilla, the anthropomorph which has better adapted to the terrestrial life), where fruits are less abundant, do not disdain the termites and the ants, and have acquired also carnivorous alimentary tendencies, eating also monkeys such as baboons, boars and small antelopes.
We must not be too much misled by the movies versions, where often the chimpanzee is shown as a sweet, nice and nasty small beast, as it were a small child. These animals can in fact become terribly aggressive; can even practice cannibalism, joining to this aggressiveness an incredible strength, corresponding to that of five adult men, so much to raise weights of 500 kg!
The chimpanzees living in the forest seldom drink, also because the assumption of the ripen fruits gives them an adequate hydration, but when they want to do it, they immerse their hands in the water and suck it.
It seems that they can utilize the leaves for drinking like a glass.
The chimpanzees move with the same agility on the ground and on the trees.
Although they are those, of all anthropomorphs, which better manage the walking with an erect posture, walking in this way for short tracts, they prefer, however, to run on all fours on the ground, leaning on their feet and on the back of the toes of the inferior limbs, kept bent inwards.
For climbing the trees, they surround the trunk with the arms and push themselves up with the feet.
They cling to the branches with hands and with feet; sometimes they travel short distances whirling from branch to branch, leaning alternatively with the fore limbs-brachiation.
The chimpanzees live in numerous communities (up to 80 individuals) not rigidly organized on the socio-biologic point of view. They stay in areas varying from 20 square km, if the food abounds, to 80 square km, if it’s matter of bushy savannah, where the trophic resources can be at times inadequate.
The home ranges overlap at times and in these cases the alimentary resources can be scarce in respect to the density of population.
Individuals of different groups can mix without showing hostility, but the mothers and the cubs tend to remain together at the centre of the community.
When the food is very abundant, several chimpanzees often gather in group for banqueting.
The adult males beat rhythmically on the exposed roots or on the ground and all others associate in a noisy choir of screams.
The resulting din can be heard even at 3 km of distance and often attracts other chimpanzees which join the group like it was a feast.
When, on the contrary, the fruits are scarce, small bands of males form and they cackle when the food is found for calling the females and the cubs on the spot.
Each evening, the chimpanzees build up, in five minutes, new platforms where to spend the night. A sort of a nest on the trees, at about 30 m from the ground, where they sleep even for 12 consecutive hours. Practically, an horizontal plane made with leafy twigs intertwined, covered by small branches and leaves for shaping a couch. Also the orang-utans do the same in the Asiatic forests.
And then often the biologists, who have difficulties in counting the chimpanzees and the orang-utans in the forest, count the nests, as it is always matter of individual couches. In the same time, the examen of the nest, based on the freshness or not of the leaves and the branches utilized for creating it, tells us if it has been built the night before or if it is there since some time.
During the rainy season, the chimpanzees can build up these nests also during the day in order to keep far from the ground which becomes a quagmire.
The chimpanzees are polygamous. A sexually mature female has the oestrum one week every four and copulates with more males. It has almost always single deliveries. Like all other anthropomorphs, the uterus is monoconcamerate, the placenta is hemochorial.
Between the chimpanzees, the rivalry for sexual reasons does not exist or is very small and there are never fixed or stable couples.
It seems that there are particularly affectionate social relations between the members of a same family, but rarely there are phenomena of incest or of consanguineous couplings.
The cubs of chimpanzee usually remain with the mother till when six years old.
During the infancy, are frequent phenomena of contact mother and son, like dynamics of socialization, these are often exemplified by a handshake between cub and mother. The chimpanzees, beyond the grooming and the smoothing of the hair, utilize frequently, also between adults, the handshake as phenomenon of socialization and friendly reassurance.
Once reached the sixth year of age, the young begin to leave the mother for longer and longer periods.
The young males join therefore the other adults, whilst the females keep a greater attachment to their own mother.
Between young males and also between sisters and brothers can take form a sort of a friendship. It often happens to see animals play together and clean the hair.
Inside a group, the chimpanzees have a personal social rank, more or less evidenced, even if is missing, as previously said, a real hierarchy, as it is on the contrary observed in some troops of guenons.
The males affirm their rank with a display of strength: with bristly hair, the chimpanzee swings rhythmically screaming, shaking branches, uprooting shrubs and throwing stones.
The male able to perform the most impressing exhibition acquires a dominant position and the other members bow in front of it or keep clear when they meet it.
Usually, the males of the same rank groom each other, kiss and join hands.
Beyond the vocalizations and the sounds related with the alimentation and the strength exhibition, the chimpanzees have a huge variety of calls and gestures.
They may accompany the friendly meetings, panting or grunting, cleaning each other, joining hands or embracing.
The alarm signal is a sound starting from low notes and then becoming acute (the well-known cry: aha, aha, aha, ahha, ahhhhaa, ahhhhhhaaaaa….) whilst the menace expression is an acute howl. When disputing, they emit cries of rage and fear.
The chimpanzees communicate also by means of an expressive gesture, thing rendering them almost unique between the anthropomorphs.
As they have developed facial muscles and a very mobile mouth, they have a wide range of expressions.
The biologist zoologists and the primatologists think that the grimace with the upper teeth discovered is a reaction of fear, whilst that where all teeth are discovered is an invitation to play. The facial expression like a pout would seem to be an expression of interest.
Finally, as said briefly before, they are between the ablest anthropomorphs manually and in the utilization of tools for specific purposes.
For instance, they can utilize a blade of grass or a small stick they insert in the den of termites and ants, to which they will stick; the chimpanzee takes it out and passes it between the lips cleaning it and eating the insects.
The gorilla (Gorilla gorilla) is usually a calm monkey, sociable, nourishing of leaves and fruits. In spite of its enormous look and the defying postures, it attacks rarely and does it only for defending the group end the cubs.
It is the greatest primate. An adult male weighs 155-190 kg and, erect, reaches the 1,80-2,00 m; a female weighs 90 to 120 kg and does not have the bony crest on the top of the head.
Usually, the gorilla walks in quadrumanous posture, keeping the arms stretched towards the ground and leaning to the back of the fingers bent against the palms. At times, it changes to erect position, when, for instance, the dominant beats its breast, during a fight, but only for a few steps. Only secondary characters differentiate the three races of gorillas.
In equatorial Africa, the most numerous is that of the western lowland (Gorilla gorilla gorilla), the less known is that of the eastern lowland (Gorilla gorilla graueri), the most known is the mountain one (Gorilla gorilla beringei).
The gorillas live in forest zones circumscribed by rivers, prairies or cultivated areas.
The mountain specimens are about 600 individuals, whilst there are no sure data about the plain races.
They live in groups which go from a minimum of 16 members up to a maximum of 30.
Each group is led by a male, the leader; at least 10 years old, with a silver grey back which indicates the mature age, and is called Silver back.
The remainder of the group is formed by females, cubs and young males which have not yet reached the full maturity and which can be recognized for the back still black.
Some groups have also other males with the grey back, but these are intruders which often leave the group.
The male leader, every day, decides where to go for the research of food. It stops eating and stands still, legs open, turned towards the direction it wants to take. The others stay around it, ready to follow where it wishes.
Every group keeps inside a territory of 40 square km, where it wanders aimlessly.
The territories of different groups at times overlap and the relevant composers look for food together.
It may happen that the youngest gorillas mix between them, whilst the adults keep at respectful distance. Some groups, however, establish friendly relations.
Between the gorillas the manifestation of affection are less warm than between the chimpanzees. At times a female lays the head on the male leading the group or a young slides on its back, but rarely the animals groom
each other or play together.
The gorillas nourish of vegetal substances: they eat leaves, sprouts, roots barks and also fruits at times. They do not need to drink as they get the water from the plants they eat, from the morning dew and from the frequent rains during the monsoon season.
Once collected the food, they break it with their hands and with the teeth, keeping in the mouth what they like and throwing away the less good parts.
The plain Gorillas (Gorilla gorilla gorilla) and (Gorilla gorilla graueri) find the best food in the thick under wood of the forest along the banks of the rivers or where some tree has fallen.
For the mountain Gorilla (Gorilla gorilla beringei) the areas more rich of dood are, o the contrary, the valleys luxuriant of ferns and lianas, and the high slopes with their juicy buds of bamboo.
The diet varies depending on the groups, even if these live in zones where the vegetation is practically the same. The gorillas spend most of their time on the ground.
The structure, heavy and bulky of the adults, especially of the males, makes them unapt for the arboreal life.
However, the young gorillas, often, climb on the trees and the adult females stop between the branches for resting and eating.
These habits of life, along with the length of their arms lead us to think that, millions of years ago, the ancestors of the gorillas had an arboreal life.
When in the plain, the gorillas build the nests mostly on the trees, even if the males prefer not to prepare them too high from the ground, 5 m maximum, or directly on the ground.
The females and the sub-adults can build them even up to 18 m of height.
On the mountains, on the contrary, where the trees , for mechanisms connected with the ecology of the altitudes are lower than in the plain, the gorillas prepare their couches on the ground.
The nests on the trees, like those of the chimpanzees, are prepared with broken branches, intertwined in such a way to form a sort of a hollow platform, concave, rounded and elastic. This capacity, which is present in the gorillas, but also in the chimpanzees and the orang-utans is a sign of a good psychic development.
The nests built on the ground are on the contrary made with a few handfuls of leaves and sheltered inside the brushwood during the rain season.
New nests are built every night.
The dominating male prepares it the first. The youngest individuals sleep usually with their mothers, or in nests built close to them.
They wake up by dawn, but remain idling for a couple of hours more. They defecate in the nest; the faeces do not stick to the body as they are hard and fibrous, seen the nature of the diet which characterizes them.
The gorillas do not couple frequently and during the copu- lation they rest, so they will take even one hour for completing it.
The dominant male is not jealous, and its females can couple with other males (polygamy) under its eyes, without causing any reaction.
The leader reacts, on the contrary, against the intruders with a stereotyped complex ritual, which includes also the famous threatening gesture of striking the chest.
This gesture renders the leader more admired and respected, thus enforcing its authority. In reality, the ritual is more complicated, in fact the dominant, in presence of the intruder, first launches a violent scream, then firm and in erect position tears off the leaves and throws them in the air. At the climax of the exhibition, the gorilla strikes its own thorax with the hands and in the same time runs left and right.
Then, on all fours, it runs in the under wood, breaking branches and hitting the ground with the hands. If at this point the intruder does not give up going away, the physical fight takes place.
There is a strong connection between the cubs and the mother: the small gorilla is cradled by the mother which carries it in its arms till when three months old.
The young begins its independent life only when the mother delivers anew, after three or four years.
The females remain always inside the group where they were born, whilst the males, once reached the full maturity leave it for going away alone or for joining a nearby group where, if the leader is by now old and weak, they can overwhelm it and take its place.
Usually, the gorilla is a calm animal, but the rare occasions when it strikes its chest and with screams it enlivens its quarrels.
Usually the gorillas, inside a group, stand few metres far away each other so that they have not to scream for tracing.
Some times, while they collect the food or while they eat it, they emit a low growl, which becomes higher is they have to call some companions which has gone too far away, when the group resumes moving.
A male surprised by the man (for instance, a biologist who is observing it) may emit a high and sudden scream of rage, but if the intruder (as always happens)gets back, the charge is just a bluff, if, on the contrary, he remains, then he can suffer physically.
The only true foe of the gorilla is the man.
Some African tribes (for instance, the Pygmies) kill the gorillas for eating them or for saving the harvests from their raids, whilst the poachers seize them because some stupid man encourages the market, buying, for instance, hands of gorillas to be used as ashtrays, on the writing desk of the office, maybe bragging of having been its hunter.
Or, they were (but this now is totally forbidden, as poaching in all its forms) seized alive for being sold to biomedical research institutes, where they were used for the pharmacologic experimentation.
Nowadays, seen the deforestation and the low prolificacy in the wild of this animal, there are few hundreds of specimens in liberty: it is in fact one of the animal species with more serious risk of extinction, protected by means of natural parks and reserves by biologists in collaboration with the local rangers and for this reason they are fully entitled to belong, unluckily, to the “Red list of endangered species” of the IUCN.
Also in this case, the zoologist biologists in the zoological gardens, zoo-parks, zoo-safaris, try by natural coupling or by artificial insemination techniques (AI), to obtain some births for the repopulation of the species, but the thing is not simple at all.
Malagasy forest, Madagascar
Isolated from 50 millions of years in the tropical-pluvial forests of the Madagascar, the lemurs, have developed, because free from the competition with other monkeys which, in other geographic zones has determined their extinction.
The lemurs are arboreal animals having remote affinities with the anthropomorphic monkeys and the human being, even if they are primates.
They are arboreal animals; the true lemurs live only in the forests of the Madagascar, but at times the zoologist biologists consider as lemurs also the bushbabies and the pottos of continental Africa and the loris of south-eastern Asia.
They are all classified as prosimians and inferior primates.
Some species of lemurs are active during the day, others in the night; many, mainly the diurnal ones, live in family groups or in bands of 2 to 12 individuals.
The night lemurs are very spread in the woody savannah; other diurnal species are confined in small areas. Usually, there is no competition for the food between different species, even if the territories do overlap.
Since when the man has appeared in the island, about 2000 years ago, many species have extinguished; one was climbing like the orang-utans of Borneo and Sumatra, another ran on the ground like the baboons.
The greatest one had the size of the present chimpanzee.
The anthropologists and archeologists who have done excavations at historical purposes in Madagascar, have found bones of lemurs together with primitive pottery, perhaps the same where the extinct human populations were cooking the lemurs.
There are three families of lemurs: the Lemurids (Lemuridae, 15 species), the Indriids and Sifakas (Indriidae, 4 species) and the Daubentoniids (Daubentoniidae, one species only). A total of 20 species, coming from a small ancestral group developed occupying the different habitats of Madagascar, after having reached the island about 50 millions of years go, maybe on drifting wood.
The ancestors of the lemurs lived in continental Africa, in Europe and in North America till when the monkeys appeared; these ones, probably, caused their extinction.
But in Madagascar, isolated and free from any competition, the lemurs have settled in those ecologic niches which, in other zoogeographic areas, have been occupied by other mammals.
The dimensions of the lemurs vary from those of the Gray Mouse Lemur (Microcebus murinus), little bigger than a mouse, to those of the Indri (Indri indri), which is about 90 cm long, is the greatest known lemur in the world and the only one tailless. It is becoming always rarer as the forest where it lives disappears.
The lemurs nourish of fruits and leaves, especially the Tamarind (Tamarindus indica), some complete their diet with insects and small vertebrates (saurians, amphibians, rodents, bats).
Even if prosimians and inferior primates, they are in condition to perceive the colours, like the human being and all other primates, the birds and few other mammals.
This helps them in choosing the partner, seen that the various species distinguish due to different colorations.
The diurnal ones have an ample polychromous range of colours: white, red, brown, yellow.
Unlike monkeys, the lemurs are sexually active only once a year.
In the case of the Maki (Lemur catta), a big lemurid as big as a cat and spread from West to South-west of the island, the reproductive period is one of the shortest between all mammals as it lasts only two weeks a year and the females of the species are in oestrum only one day.
Before the reproductive period, the male has a violent attack of aggressiveness which manifests in fights, chases and violent brawls.
During these fights, the males clash shaking the big tail or a small branch, after having soaked them with their own odorous secretion. In this respect, we have to say that both in the lemurs and in the makis are present odoriferous glands at the base of the hand (wrist), whilst the feet have a long cleaning nail.
These symbolic tournaments cease when the female is in heat. By that time the males fight truly, hitting with the long canines. Once fight is finished, the winner mates with the female.
The propithecus, called by the natives “Sifakas”, are great lemurs, about 1 metre long, tail included, of the family of the Indriidae. There are two species known: the (Propithecus verreauxi) endemic to the forest of Verreaux and present in the north-western area of the island, and the Propithecus coronatus, living in the eastern pluvial forests.
The sifakas are usually more docile than the Makis (Lemur catta). Rarely happen fights inside the groups, but, instead, they exhibit in ritual fights with the members of other groups for the defence of own territory which extends for about 12 hectares for a group of five lemurs.
They mark their territories both with odorous secretions and with urination.
When they leave the forest, thing which happens quite rarely, the propithecus go forward hopping on the ground, erect, leaning with the feet united and raising arms by each hop. The social relation which unites the individuals of a group is the reciprocal grooming, which stimulates the dynamics of socialization via contact; the members, in fact, spend part of their time scratching and combing each other with their dental combs, which do the cleaning with a singular “brush”.
It is matter of a fringed structure, placed under the tongue, called sublingual structure the animal pushes forward when it has to clean the dental combs from the hair.
The cub of sifaka keeps stuck to the maternal back during its infancy. It begins to walk alone when 6 weeks old, but remains however close to the mother for a period of about 5 months.
A phenomenon present in all primates, called “Affective Awareness” by the biologists, has been observed in the Lemur catta.
When during a period of severe drought a group of Lemur catta moves looking for a source of water, it may happen that the mother with the cub, almost completely dehydrated, faces a difficult affective choice.
After a stop for refreshing, the group starts again, but the cub has not any more the strength to keep clinging on the maternal back.
The group is already going; the mother tries to pick up the young which it cannot keep on an arm, as the type of walking characterizing these animals involves all four limbs.
The force of selection and of survival obliges instinctively the mother to reach the group looking for water for surviving, but the female, which sees and hears the cub, fallen on the ground, emitting weak laments, goes back at least six times, trying to push it, aware that it’s losing it.
What has been observed it is the sign that also in the primates not so much evolutionarily developed like the prosimians, does exist an affective conscience, which was defined as “Affective Awareness” by the zoologist biologist present to the event who took care of the cub, saving it.
Most of the small sized lemurs are nocturnal animals.
The gray mouse lemurs, for instance, spend the day in nests or live on the trees. They are social animals and even 15 of them can be found in a single nest.
Three species are known: the Gray Mouse Lemur (Microcebus murinus) of the southern regions of Madagascar, the Red Mouse Lemur (Microcebus rufus) for the northern and eastern zones, and finally the Coquerel’s Mouse Lemur (Microcebus coquereli) of north-western Madagascar.
The cheirogaleus, much smaller than the squirrels, are the primates which hibernate.
The Fat-Tailed Dwarf Lemur, also called Lesser Dwarf Lemur (Cheirogaleus medius), endemic to the central-south western area, in fact, falls into summer lethargy for several weeks. It has an enlargement at the base of the tail where it stores the deposit fats which are used for nourishing it in July-August, during the dry season, when its activity ceases and falls in summer rest (estivation). It is a solitary and nocturnal animal, rarely visible by day time.
The Greater Dwarf Lemur (Cheirogaleus major), endemic to the oriental belt of the island, has, on the contrary, only a lethargy of a few days.
The Weasel Lemur (Lepilemur mustelinus), unlike the other lemurids, does not run on all fours, but jumps on the back ones, like the indriids. Finally, the oddest of all lemurs, is the Aye-aye, belonging to a separate family, that of the Daubentoniids (Daubentoniidae).
It has the size of a cat, and enormous ears, similar to the bats’ ones. Incisors, like rodents and the third finger of the hands, long and very thin, provide with a long and bent nail which is utilized forextracting from the old branchesor from the trunks, the larvae which eat the wood.
The technique consists in hitting the trunk, about eight times a second. The difference of the sound intensity, caused by the presence of the larva, is perceived by the acute hearing of the animal, which locates it, seizes and eats.
The aye-aye (Daubentonia madagascariensis) is on e of the rarest mammals in the world.
Once, it lived in all forests of Madagascar. Now are extant only about 50 specimens, present in the coastal pluvial forests of the African island. Obviously, it belongs to the Red List of Endangered Species of the IUCN.
Last, the Varecia variegatus, a lemur, not much studied because not easy to be observed. It has black or red drawings on the coat, and is 90 cm long plus many more of tail: remarkable dimensions for a lemur.
It lives in small groups in the eastern pluvial forests of Madagascar.
Tropical forests of Centre and South America
The resemblance, as ecotypes, of the tropical forests of the New and Old World has been the reason of the parallel evolution of two groups of monleys, not strictly close, but similar.
The monkeys of central-southern America are united in two families: the Cebids (Cebidae) and the Callitrichidis (Callitrichidae), the most ancient of the New World.
None of the two families has strict affinities with those of the Old World,even if their members, resemble in the appearance, because, as said, they have adapted to live in very similar biotopes.
The monkeys of the New World differ from those of the Old one for three important characters: they have three premolar teeth for each side of every jaw and not two; the thumb cannot be opposed to the other fingers, that is, does not bend against the remainder of the hand (so that, when they seize an object, they hold it between the fingers and the palm); and, last, have broad, lateral, distant and oblique nostrils, instead of central and low placed as in a chimpanzee or a gorilla.
This difference gives the name to the whole group of the New World monkeys, called in fact Platyrrhines (Platyrrhini, that is with a flat nose).
All monkeys of central-southern America are arboreal; they can be found only in the forests and none of them has the tail so reduced, as on the contrary happens for the baboons and the macaques of the Old World, which have terrestrial life.
The callitrichidis, of which 21 species do exist, are the only superior primates which have claws instead of flat nails. Agile climbers, they go up on the trees like squirrels, embedding their long claws between the barks of the trees, instead of clinging to the branches with hands and feet as done by the other monkeys.
They have slender bodies, flexible and long prehensile tails. On the ground, they walk with hands and feet. These monkeys resemble each other for structure and habits, much more than the members of the family of the cebids, which, on the contrary, form a little homogenous group.
The multiple deliveries of these animals are the norm, and most of the species live in family groups. For these reasons, the family of the callitrichidis is usually considered as the oldest of the monkeys of the New World.
Almost all the monkeys of the genus Callithrix, measure little more than 50 cm, of which about thirty concern the long tail and have long inferior teeth, with which they clean up their nice silky coat.
The Marmosets divide in two genera: Callithrix, 3 species, and Cebuella, one species.
The white-tufted marmoset (Callithrix jacchus) live mainly in the highest part of the tops of the trees. It nourishes mainly of insects, but alsoof fruits and leaves. During the night, its temperature decreases of 1°c, unique fact I the monkeys.
The marmosets live in family groups formed each one by a couple of parents and by their offspring.
The male marks its territory with the odour of its scrotal glands, which it rubs against the branches. It menaces the nearby males, quickly raising and lowering the tufts of the ears and arching the back.
The reproduction takes place at any time of the year. During the courting, the male exhibits walking with arched back, smacking the lips and pulling out the tongue.
The components of the couple leak the hair and groom each other, delicately, using the inferior incisors.
After an about 5 month’s long gestation, the babies come to life, usually two, at times even three, rarely only one.
They are carried in the arms by the male and given to the mother for the nursing only.
The young begin to walk alone around the third week of post-natal life, becoming completely independent by the fifth month of life.
The Geoffroy’s Marmoset (Callithrix geoffroyi) is a graceful small monkey with a white face which spends most of its time cleaning its own hair.
The Pygmy Marmoset which afferent to the genus Cebuella, (Cebuella pygmaea) is the smallest extant monkey, little longer than 13 cm, with an about 20 cm long tail. It has no tufts on the ears and the fur on the head, falling backwards like hair, hides the ears.
The female delivers always two cubs, which are carried in the arms by the father and given to the mother only for nursing.
In substance, in the marmosets we observe that the parental cares are more a duty of the father than the mother’s, unlike what usually happens in the Animal Kingdom.
They are endemic to the tropical forests of Central America (mainly Mexico, Costa Rica and Panama) and to the forests of South America (Bolivia, Peru, Brazil, Colombia and Uruguay).
The Lion monkeys (genus: Saguinus, 13 species; genus Leontideus, species) are taller, as body and tail reach almost the 40 cm each. The thick mane and the reddish colour of the fur have given it this name.
The cubs are carried by the father, hidden into the long and thick hair, for 6-7 weeks of post-natal life, and are given to the mother only for being nursed.
The species of the genus Saguinus, are nervous and aggressive; the are recognized for the white hair around the mouth (in many species) and for the absence of the long incisors.
The Midas Tamarin (Saguinus midas) lives in the valley of the low part of the Amazon River. It is active since early morning and nourishes in the low layers of the trees. With the progress of the day, when the temperature increases, the Midas climbs in the thick shadow of the vault of the forest, effecting, between the branches, even 7 m long jumps.
The midas live in family groups formed by parents and offspring, up to 4, on a territory which they defend with high and acute cries.
The graceful Oedipus, leonine monkey of the genus Saguinus, like the species Saguinus oedipus, with notched ears and the candid crest of hair on the head, is little bigger of the similar species and it also effects long jumps between the branches.
It rests under the sun, lying face down on the branches, with arms and legs dangling. When it stands up, it walks erect. Also this species lives in family groups, formed by parents and sons, on a territory the defence of which is duty of the adult female. The animals clean each other with their tongue.
During the courting, the female excites the male urinating on its own tail and sprinkling it with the odorous secretion emitted by a gland placed at the base of the tail itself. Usually, two cubs come to life at the same time.
The Leontideus rosalia belongs also to the leonines of the genus Leontideus.
The callimico (genus Callimico, one species) seems to have characters common between the family of the Callitrichidae, the most primitive of the New World, and the family of the Cebidae, therefore can be considered as the conjunction ring of the two families. Usually it is completely black, and like other leonine monkeys, has a long mane around the head.
As briefly said, it resembles to the members of the family of the Cebidae. It has also a third molar, and the female delivers in this case only one cub a time. The sons are carried exclusively by the mother until when they are three weeks old, then and only by then, are carried by the males. An example is the Callimico goeldii.
Both the leonine of the genus Saguinus and Leontideus, as well as the Callimico are zoogeographically endemic to the tropical forests of South America, in particular, Bolivia, Peru, Uruguay, Venezuela Colombia and Brazil.
The members of all these genera have extremely long prehensile tails, with flexible extremities and similar to fingers, so much that we can even talk of “fingerprints”.
The family of the Cebidae has members having a greater radiation, because more adaptable physiologically.
They are located in almost all the tropical forests of South America, from Colombia to Venezuela, to Brazil (Amazonian forest), to Peru, Argentina, Uruguay and Paraguay.
This family includes some of the noisiest and biggest monkeys of the New World, in particular of South America, like the howler monkeys, with vocalizations which can be heard even 5 km far from the origin point.
The family of the Cebidae includes 26 species of South American monkeys, each one adapted to a particular type of life.
Usually, they are bigger monkeys than the callithrichids, have fingers rather flattened, provided with nails instead of claws; the females deliver one cub only at a time; monotocous or monovular species.
Furthermore they have in their ranks the only nocturnal monkey in the world and several species characterized by having a prehensile tail. The titis or callicebus (genus Callicebus, three species), such as the Callicebus moloch, live in the basin of the Amazons, in the thickness of the forest.
The Callicebus moloch resembles to the marmosets, for the position assumed on the trees, with the limbs and tail dangling; these monkey live in pairs and sleep with their tails intertwined. They form hunting territories, which they defend from their like. Every pair, with the cub, usually carried by the male, emits by dawn before the meal, a long and plaintive cry.
The Duruculi or Aotus (genus Aotus, one species, Aotus trivirgatus), the only superior primate with nocturnal life habits, has great eyes and white eyelids, called also owl monkey for the resemblance with this strigiform.
Active by dawn and sunset, it nourishes of fruits and insects. Lives on the trees at 25 m from the ground and never goes down under the 2,50 m. The duruculis live in pairs, male-female, and the males pommel the intruders. They mark the territory spreading urine on the trees.
The Pithecias and the Sakis (genus Pithecia, two species), for instance the White-faced Saki (Pithecia pithecia) and the Monk Saki (Pithecia monachus), the Uakaris (genus Cacajao, three species) like the Red Uakari (Cacajao rubicundus) and the Bald Uakari (Cacajao calvus) and the Satanas or Chiropotes (genus Chiropothe, two species) like the Satanas (Chiropotes satanas) and the White-nosed Satanas (Chiropotes albinasus), have all coarse hair, canines and lower incisors very developed.
The Monk Saki (Pithecia monachus) takes its name from the hood of long hairs coming down before on the shoulders.
The Satanas (Chiropotes satanas) and the white-nosed (Chiropotes albinasus) have beard and tufts around the face.
The pithecias and the satanas called Saki, like the White-faced Saki (Pithecia pithecia) have long prehensile tails.
The Bold Uakari (Cacajao calvus), a smart climber, has a short tail and shaggy coat; face and head almost bare, the head is looks like a skull, and does not present adipose strata on face and head. The face is pink in one race, red in another.
The squirrel monkeys (genus Saimiri, two species), like the Saimiri sciureus an insectivore, eat also flowers and berries, have a white face with black hoods and muzzles. They live mainly in the forestall areas along the rivers, in group of even 500 specimens, organized, depending the sex, in determined ranks. When eating, they wind the tails around the branches for sustaining.
However, their tails are not really prehensile. The squirrel monkeys, in fact, cannot hang with the tails, like the capuchins (genus Cebus, four species), bigger and more robust.
The Cebus apella is called Black-capped or Tufted Capuchin due to the presence on the head of spiky hair which form the lateral tufts. It is a vey intelligent monkey, present in the forests along the rivers and close to the estuaries, where the cyclic phenomenon of the tides is more evident.
It is able to read this geophysical phenomenon and to foresee the ebb tide which, reducing the level of the river, allows to find and pick up the molluscs under the stones.
The presence of a psychic consistency of a good level in these animals is observed also by one odd alimentary habit they have.
Having no mandibles, jaws or robust teeth, like the Japanese macaques, for breaking the shells of the molluscs, the rub them and hit them several times against a trunk of a tree. This is not enough, by sure, for breaking them, but in the long run it loosens the muscle contraction of the mollusc which, at the end, is obliged to open the valves and so being eaten.
The other species of the genus Cebus, known as capuchins (Cebus capucinus), do not have tufts, but a sort of characteristic black cap, formed by longer hairs, are known also as ringtail monkeys, because they hold the tail coiled while walking on the branches.
The cub clings to the hair of the mother’s belly just after the birth, and when strong enough, it settles on the maternal back.
They live in groups, which count up to 50 individuals in the medium levels in the forests of central and southern America.
The woolly monkeys (genus Lagothrix, two species) have also a prehensile tail. The most common, the Lagothrix (Lagothrix lagothricha), lives in numerous groups between the points emerging at the top of the forest, usually near wetlands.
The spider monkeys (genus Ateles, two species) have a thinner body if compared to that of the similar woolly monkeys.
But the Ateles arachnoides, the other species (Ateles paniscus) has shaggy hair, and, having no thumbs must cling to the branches with four fingers only. In return, it has the maximum expression of prehensile tail, which it uses as a fifth limb, thus compensating the missing finger in the hands. This tail has a flexible tip, with a terminal bare area which has a real fingerprint, similar to that of the fingers of hands and feet. It allows a very strong grip, and the animals can safely hang upside down, clinging with the tail on a robust branch.
The monkeys of the genus Ateles can walk erect on the ground for short tracts, or otherwise, creeping. They sleep in groups of 100 individuals and disperse during the day looking for food. They communicate through acute cries and discourage the intruders with deep grunts or throwing branches and excrements.
The howler monkeys (genus Alouatta, five species), between which we have Alouatta villosa, have in the throat a pharyngeal apparatus exceptionally developed, so much to show a swollen neck. They can emit very strong cries, which can be heard even at 5 km of distance!
The howlers live in troops of a twenty individuals, having about two adult males for every seven females. Usually they cling on the highest branches, passing from a branch to another, through a bridge done with the hands on one side and the feet plus the tail on the other.
When two groups meet casually, a vocal fight takes place. If then some intruders enter the territory, these ones are received throwing them branches, urine and faeces.
Active during the day, they eat vegetables, insects, eggs of birds or reptilians,
small vertebrates, amphibians, saurians and small birds.
The young of these monkeys which spend their infancy clinging to the maternal hair, depend from the mother till the tenth month of post-natal life.
North Africa, savannahs and prairies of sub-Saharan Africa
We have several times said that as most of primates (prosimians, apes, hominids) of the Old and New World are endemic to evergreen tropical-pluvial forest biotopes, characteristic uniting them and determining similar morphology, even if they are different species living thousands of kilometres far away.
Although if the evolution of monkeys has mainly developed in the forests, eight species have invaded the savannah habitat adapting to it, whilst one lives in North Africa, in bushy-woody and rocky biotopes, like the slopes of the Moroccan Atlas.
It is matter of the Barbary Macaque (Macaca sylvana), the only monkey belonging to the Mediterranean fauna, present in particular in the woody highlands of Morocco, Algeria, Tunisia and the Rock of Gibraltar, where their presence is thought of having been caused by the flight of North African specimens.
Due to their affectionate nature towards the man and their easy domestication, the Barbary macaques were often embarked as companion animals on the commercial vessels which were sailing from North Africa to Gibraltar.
It is possible that some escaping specimens (feral species) have well adapted to the life on the Rock, which has a climate and physic geography very similar to those of their origin countries.
The elevated rate of fertility has completed the job, so much that still nowadays the Barbary macaques of Gibraltar are one of the most important fauna attractions of this small strip of English land.
The English royal family was spending often the holidays there, finding the nice animals an essential element which was rendering the place even more exotic of what it was already.
By the early fifties, an infective pathology, probably transmitted by birds (ornithosis), caused a sudden decrease of these monkeys, and immediately Winston Churchill, English Prime Minister of the time, arranged the import of several specimens of Barbary macaque from North Africa, as their absence should have rendered the Rock of Gibraltar less characteristic and less satisfying for the royal family (God Save the Queen!).
The Macaca sylvana is tailless, and this is the only characteristic rendering it similar to the great anthropomorphic apes, from which, however, it differs totally.
It is similar to the monkeys of India, the South-East Asia and the Sub-Saharan Africa
Like many monkeys the magot is sociable, even if subject, as it happens for several cercopithecoids, to sudden outbursts of anger associated with jumps and cries.
It lives in small crowds moving in rocky and woody regions looking for animal food (insects, small saurians, birds, birds and reptilians eggs) and vegetal (sprouts, plants, flowers, bulbs).
Among the aforementioned eight species living in the savannah areas present in all Sub-Saharan Africa, in western, oriental and central-southern Africa, five are cynocephalic: the Hamadryas baboon (Papio hamadryas), the Baboon in the literal sense, or Yellow baboon (Papio cynocephalus), the Olive or Anubis baboon (Papio anubis), the Guinea baboon (Papio papio) and the Black or Chacma baboon (Papio ursinus).
Among these five species, the hamadryas prefers to live in the arid-rocky regions.
The baboons are the most common monkeys in Africa, and some biologists consider them as races actually belonging to a single species, the Hamadryas (Papio amadryas).
The remaining three species are cercopithecoids, also called vervets, patas and grivets in Kenya.
It is matter of the Hussar monkey (Erythrocebus patas), living in the steppes and the grassy savannahs South of Sahara; of the Greyish-green vervet (Cercopithecus aethiops ), living by the boundaries between forest and savannah; and of the Gelada baboons (Theropithecus gelada), common in the temperate prairies on the Ethiopian mountains.
The resemblance between the hamadryases and the geladas (body covered by long hair) are and adaptation to similar ecological life conditions, much more than to a real relationship.
All savannah baboons form huge groups with several males, whilst there is one male only in each group of hamadryases, geladas and hussar monkeys.
This reduction corresponds without any doubt to a life adaptation to an arid habitat.
As a male can fecundate whatever number of females (polygyny), all others are eliminated from the group and abandoned to their destiny.
The presence of more males is possible, in fact, only where abundant trophic resources are present.
The number of baboons in a troop is much variable. An average of 27 in the arid regions of south-western Africa, of 46 in Rhodesia and of 80 in the Amboseli National Park, in Kenya.
During the displacements from a territory to another, the dominant males of a troop and the females with the infants proceed at the centre of the troop.
The lower rank males and the young of both sexes are located around them, always ready to give the alert, like sentries, in case of danger.
Each troop disposes of a territory around the trees where the baboons sleep during the night.
By day time, they come down to the ground, wandering in the savannah looking for seeds, grass and fruits.
During the dry season, they can dig holes deep up to 25 cm, looking for bulbs and roots.
When the vegetal food is scarce, they eat insects, saurians, reptilians and birds eggs, and in some troops formed by specialized individuals, they kill hares, small birds, saurians and even young gazelles or flamingos.
All adult males dominate the females.
Between these ones does not exist a permanent hierarchy, but a female with the infant gets temporarily a higher rank (breeding period).
Between male baboons, the hierarchy is rigid; even if it may happen the two males join against a third one, which, at his turn, dominates them separately.
When the hierarchy is well fixed, the dominating male, which is the most aggressive and vigorous, has practically the exclusive control of the couplings with the females in oestrum and therefore, is the father of the 80% of the young belonging to the following generation.
The other males are free to couple with immature or non in oestrum females.
The young males are extremely eager to fight as they often try do advance in the social hierarchy.
The hamadryases have their own social-biologic particularity.
The troop is divided in groups; each one includes one male only and up to six females, whilst the single males form a different group.
During the day, the groups look for food separately, but by night they unite for sleeping.
The females follow the male; this one remains for all the life together with the females with which it couples.
In the other species the males do follow the females and the pair lasts only for the time the female is in oestrum.
The male hamadryases do not allow the external males to seize their own females. But they are absolutely not jealous on the sexual point of view.
As a matter of fact, the dominating male allows a two years old to couple with three-four years old females.
When three or four years old, the male of hamadryas begins to form its own troop, taking away a young female from the mother.
Two years later, it adopts the orphans of both sexes and at last finds a final female.
When this one is in oestrum, the two mate and their union becomes sexual and social at the same time.
The male hamadryas when meeting a foreign female, tries to get it into its troop, but does not try to couple with her at once.
When a male dies or loses, in a fight, the right to the females, these ones begin to follow the other male, which at times can even be single.
The male hamadryases, like other baboons, are very caring for their offspring, which they follow with devotion.
If a young is menaced by another member of the troop or by a predator, they exhibit their powerful canines, as big as those of a lion and, if necessary, they use them.
If a young male realizes that the dominant of the troop is too strong, it submits to him, showing the callosity of its back, in the same position adopted by the females in heat for stimulating the males for the coupling.
During the displacements, it may happen that a female of the harem does not follow the dominating male closely enough, in which case the male may bite her for recalling her to the order, getting obedience at once.
The Geladas (Theropithecus gelada), like the hamadryases, form several troops dominated by one male only, and these, at their turn, unite forming bigger groups.
In any case the relations between the members differ in the two species, both inside each group and between the various groups which form the unified troop.
A hierarchical order forms between the gelada females: each one surveys that of immediately lower rank, and does its utmost for keeping it far away from the male.
As a consequence, the reproduction probability decreases depending on the dominance order, whilst the females of the Yellow baboon (Papio cynocephalus) do have all the same possibility to get descendants.
The Hussar monkeys (Erythrocebus patas) live in troops formed by a male and up to 10 females with their infants.
The troops have a 50 square km territory each and meet rarely.
Usually, they do not cover more than 800 m per day, looking for insects, birds and reptilian’s eggs and fruits.
A form of hierarchy does exist between the females: the dominating female directs the displacements of the whole group.
Excluding the reproduction functions, the role of the male is that of a sentry.
It lives away from the group, and in case of danger, when it sees a leopard, a hyena, a wild dog or a cheetah, in order to protect the troop, it advises of the presence of the predator with cries, leaps and shaking the branches, and distracts it while the troop runs away.
The separation of the male from the rest of the group and the lack of contact between different groups are unique instances among the primates.
The Hussar monkeys lean in their tail in order to see above the high grass.
They are very well adapted to the terrestrial life, as they have long limbs, short fingers and a thin body, like that of a greyhound.
Due to these characteristics, they are agile and rapid.
The males weigh about 13 kg, the females 5-7.
The coat is dark red, but the lower and back parts, white in the adult male and pink in all females and sub-adults.
The Greyish-green vervets (Cercopithecus aethiops) live close to the edges of the forest, where the fruits and insects are more abundant than in the open savannah.
They hold the lowest social form of organization between the savannah monkeys.
They are divided into small groups from six to twenty individuals of all ages; the number of the females is slightly superior to that of the males.
These ones dominate the females, but a hierarchical order between them is not noticeable, even if, when we have to manage with species with social biology like the primates, this is difficult to be clearly defined.
Long studies are necessary, and in the case of the greyish-green vervet, these ones are still to be thoroughly effected by the ethologists.