Comparative Primate Post

Lemurs

All lemurs are found only in Madagascar (an island off the coast of Africa), and the neighboring Comores Islands. But on these islands, lemurs live in a variety of habitats. Some live in moist, tropical rainforests, while others live in dry desert areas.

Lemurs play an important role in the ecology of Madagascar and the Comores Islands, because they disperse seeds from the fruit they eat. These seeds can then grow into new plants, which is important because the forests of Madagascar are being destroyed at a very high rate.

Mating & Sociality

Ring-tailed lemurs have an extremely short mating season; it has been described as being “brief and bloody”. The mating season occurs in April and lasts less than two weeks, and a single female receptive to males for only one day out of the entire year. The female estrous is very visible, during which the genetalia swells from 1.5 to 3 cm in length and develop a pink center. Synchronization of mating activities between sexes as well as synchronization of the menstrual cycles among females has been observed in many primate species (including humans), and the most extreme example of this is found in lemurs. All adult females in a number of adjacent groups were found to become receptive at the same time. This synchrony of breeding is probably achieved through olfactory communication, since lemurs’ several scent glands are used most extensively during the breeding season. Female ring-tailed lemurs first give birth at 3 years of age, and will continuously give birth every year following. Single births are most common, though the occurrence of twins has been found when the female is in very good health and resources are abundant. Due to the synchronization of breeding activity, all infants in a troop are born within a matter of days.

Our human intellect has resulted from an enormous leap in capacity above the level of monkeys and apes. Earlier,though Old and New World monkey’s intelligence outdistanced that of other mammals, including the prosimian primates. This first great advance in intelligence probably was selected through inter-specific competition on the large continents. However, even at this early stage, primate social life provided the evolutionary context of primate intelligence

Two arguments support this conclusion. One is ontogenetic: modern monkeys learn so much of their social behavior, and learn their behavior toward food and toward other species through social example. The second is phylogenetic: some prosimians, the social lemurs, have evolved the usual primate type of society and social learning without the capacity to manipulate objects as monkeys do. It thus seems likely that the rudiments of primate society preceded the growth of primate intelligence, made it possible, and determined it’s nature.

Lemurs are threatened largely because their habitats are being destroyed. People in Madagascar cut down the forests there to use the wood, and to grow agricultural crops in its place. In fact, eighty percent of the lemur's original habitat in Madagascar has been destroyed. Although the lemurs themselves help to disperse seeds for new plants, they cannot keep up with the people that cut the forests down. Lemur populations are also hurt by hunting. Fortunately, however, all types of lemurs are protected by CITES, which makes it illegal hunt or capture lemurs for trade, except for scientific research, and to breed in zoos. These laws are well-enforced, and the lemur has been a long-time focus of conservation efforts. But although the lemurs are no longer being hunted as much as in the past, deforestation is still threatening their survival.

Spider Monkeys

The spider monkey is considered a primitive new world monkey. They are called spider monkeys because they look like spiders when they are suspended by their tails.

Spider monkeys are usually all black, but some have flesh colored rings around their eyes and white chin whiskers. Their hair generally coarse and stringy, it lacks under-fur.

Colors: golden, red, buff, brown or black, with hands and feet generally black.

Their brains are less complex, their thumbs are not opposable and their nostrils are further apart. These monkeys depend highly on their keen binocular vision. They have slender bodies and limbs with long narrow hands. 

This arboreal monkey has a prehensile tail that is muscular and tactile and is used as an extra hand. The tail is sometimes longer than the body. Both the underside and tip of the tail are used for climbing and grasping and so the spider monkey uses it like a fifth hand. When swinging by the tail, the hands are free to gather food.

The spider monkey's arms and legs are particularly long too. It has hooked-shaped hands because its thumbs are either absent or reduced to a stump. Hands are like hooks with long, narrow palms, long curved fingers, and no thumb. Head is small, muzzle prominent. They have thumbs on their feet only.

Male body length 38-48cm, tail 63-82cm, 9-10kgs. Female body length 42-57cm, tail 75-92cm, 6-8kgs. Males and females look the same.

Sociality & Mating

Spider monkeys live in medium-sized, loosely associated groups of about 30 individuals. The females have a more active leading role than males, so their social system is thought to be matriarchal. Within the group, adult males can coexist peacefully, although there is a clear hierarchy determined by age. The group is centered on the females and their young. Males are dominant over females, but it is the females that make the key decisions for the group. Males may forage in small groups. Females and offspring often forage alone.

When threatened, they make barking noises, but if that doesn’t scare intruders away, they fragment into subgroups and run. They prefer retreat, so fights are rare.

Every 2 – 3 years, a mother will give birth to one entirely black baby. No one else besides the mother looks after the baby. The baby is continuously carried by the mother, clinging to her and at about 5 months of age it will begin riding on her back, wrapping its tail around the mother's tail for additional security. It will be dependent on its mother's milk for 2 years. Juveniles at the age of 24 to 50 months old never ride on their mother's back but they will still stay close to her. They spend their time exploring, or chasing, grappling, and jumping on others. They will play with others their same age or with adults.

Baboon

Baboons are the largest of the Old Word monkeys. There are five distinct subspecies. Each occupies a distinct portion of the total range of the species. This has led some scientists to believe that each of the five could be considered a separate species in its own right.
Baboons live in well-organized troops, and the individual is only secure within his or her own troop. Large, dominant males rule the group and are responsible for keeping order among quarrelsome members and for protecting the group from predators. They communicate in several ways, including posture, the way they hold their tails, screeches and yelps. Baboons walk on all four limbs, with their tails held in a characteristic arch.
Sociality & Mating

The size of baboon groups is amazingly variable from less than 10 to almost 200 .Different kinds of baboons that live in very different habitats tend to differ in group size. But even within a population such as Amboseli, group size differs at different time periods and even among groups at any one time. Habitats richer in food resources tend to support larger groups, and if groups get somewhat large for a particular habitat they will often 'fission' or split. These fissions tend to be along lines of genetic relatedness and 'friendship', and usually seem to be driven by decisions of females. Fissioning can leave a group more vulnerable to predators, however, so to some extent group size may represent a compromise between food availability and predator risk, a balance that may differ among habitats, even within one population and also that may shift over time.

For a wide range of primate species, the number of mature or fertile females in a group is a major determinant of how many adult males will be in the group. In Amboseli, males tend to leave groups if they have had low mating success and to join ones with a relatively low ratio of adult males to females. But some males who have fathered a number of infants in a group stay in that group for a considerable period after they are reproductively successful; this may result in benefits for their immature offspring. Much is left to be learned about the determinants of size in primate groups despite this being a topic with a long and active history.

Baboon mating behavior varies greatly depending on the social structure of the troop. In the mixed groups of savanna baboons, each male can mate with any female. The mating order among the males depends partially on their social ranking, and fights between males are not unusual.

There are however more subtle possibilities; in mixed groups males sometimes try to win the friendship of females. To garner this friendship, they may help groom the female, help care for her young, or supply them with food. The probability is high that those young are their offspring. Some females clearly prefer such friendly males as mates. However, males will also take infants during fights in order to protect themselves from harm.

A female initiates mating by presenting her swollen rump to the male. But "presenting" can also be used as a submissive gesture and is observed in males as well. This submissive gesture has many unspoken meanings amongst the troop. The dominant males often engage in what is known as a false-mount, in which they mount the submissive males. It is a sign of dominance, and happens very commonly to younger males in the troop.

Females typically give birth every other year, usually to a single infant, after a six month gestation. The young baboon weighs approximately one kilogram and has a black epidermis when born. The females tend to be the primary caretaker of the young, although several females will share the duties for all of their offspring.

After about one year, the young animals are weaned. They reach sexual maturity in five to eight years. Baboon males leave their birth group, usually before they reach sexual maturity, whereas females are "philopatric" and stay in the same group their whole life.

Gibbon

Gibbons are rare, small, slender, long-armed, tree-dwelling apes. These very acrobatic primates live in southeast Asia. Gibbons are arboreal; they spend most of their lives in trees. Because they are so dextrous while moving in the trees, almost no predators can catch them. There are nine species of gibbons, including the siamang, which is the largest and darkest gibbon. Because of the rapid deforestation of their habitats, gibbons are an endangered species.

Sociality & Mating

Gibbons are social animals that are active during the day (they are diurnal). They live in small, stable family groups consisting of a mated pair (a male and a female who mate for life) and their immature offspring (juveniles, gibbons less than 7 years old).

Gibbon mates usually stay together for life. They are fully grown and able to reproduce at 12-13 years old. Female gibbons are pregnant for about 7 months and usually have a single baby at a time; twins are rare. Newborn gibbons are hairless except for a small cap of fur on the top of the head.

Female gibbons carefully nurture their young. Babies can grasp their mother's fur to cling to the mother's belly soon after birth. They are weaned at about 1 year old. Young gibbons stay with their mother for about 6 years. The young then venture out (or are forced out by the same-sex parent) to start a new family group of their own.

The earliest-known primates date from about 70 million years ago (Macdonald, 1985). The greater apes (family Pongidae, gorillas, chimpanzees, bonobos, and orangutans) split off from the lesser apes, gibbons and siamangs) 20 million years ago. Gibbon-like fossils have been found in Africa (from the Oligocene and Miocene), Europe (from the Miocene), and Asia (from th Gibbon populations are decreasing; they are threatened with extinction. Gibbons are losing their natural habitat because human agriculture is encroaching on it. Population numbers are decreasing. There are estimated to be about 79,000 lar gibbons (the white-handed or common gibbon).
e upper Pliocene and Pleistocene).

Chimpanzee

Chimpanzees are our closest living relatives, sharing more than 98 percent of our genetic blueprint. Humans and chimps are also thought to share a common ancestor who lived some four to eight million years ago.

Chimpanzees live in social communities of several dozen animals, and can habituate themselves to African rain forests, woodlands, and grasslands.

Although they normally walk on all fours (knuckle-walking), chimpanzees can stand and walk upright. By swinging from branch to branch they can also move quite efficiently in the trees, where they do most of their eating. Chimpanzees usually sleep in the trees as well, employing nests of leaves.

Chimps are generally fruit and plant eaters, but they also consume insects, eggs, and meat, including carrion. They have a tremendously varied diet that includes hundreds of known foods.

Chimpanzees are one of the few animal species that employ tools. They shape and use sticks to retrieve insects from their nests or dig grubs out of logs. They also use stones to smash open tasty nuts and employ leaves as sponges to soak up drinking water. Although chimps and humans are closely related, the apes have suffered much at human hands. These great apes are endangered and still threatened by bushmeat hunters and habitat destruction ome basic human sign language.

Mating & Sociality

Females can give birth at any time of year, typically to a single infant that clings to its mother's fur and later rides on her back until the age of two. Females reach reproductive age at 13, while males are not considered adults until they are 16 years old.

Although chimps and humans are closely related, the apes have suffered much at human hands. These great apes are endangered and still threatened by bushmeat hunters and habitat destruction.

The common chimpanzee has a and the groups at any one time could be of the following types: all-male, adult females and offspring, bisexual, one female and her offspring, and single individual. This species has a promiscuous mating system. These communities have ranges that overlap with other groups .The core of the society are the males, who roam around and protect members of the group as well as hunt. There is generally a dominance hierarchy amongst the males. Males are philopatric while females are the ones who will disperse. Females in the group that are not related will not show much interaction. Males will start to associate with adult males more as they become older, and they will be integrated into the hierarchy by adulthood. Infanticide has been reported for this species, and it happens when an adult male kills the infant of an unfamiliar female. Male-male associations are the strongest in the group, with grooming and food sharing occurring between males. Within the male hierarchy, alpha status is often gained through forming coalitions with a brother or an older non-relatives.

Baboons sleep, travel, feed and socialize together in groups of about 50 individuals, consisting of seven to eight males and approximately twice as many females plus their young. These family units of females, juveniles and infants form the stable core of a troop, with a ranking system that elevates certain females as leaders. A troop's home range is well-defined but does not appear to have territorial borders. It often overlaps with the range of other baboons, but the troops seem to avoid meeting one another.

When they begin to mature, males leave their natal troops and move in and out of other troops. Frequent fights break out to determine dominance over access to females or meat. The ranking of these males constantly changes during this period.

Males are accepted into new troops slowly, usually by developing "friendships" with different females around the edge of a troop. They often help to defend a female and her offspring. Baboons sleep, travel, feed and socialize together in groups of about 50 individuals, consisting of seven to eight males and approximately twice as many females plus their young. These family units of females, juveniles and infants form the stable core of a troop, with a ranking system that elevates certain females as leaders. A troop's home range is well-defined but does not appear to have territorial borders. It often overlaps with the range of other baboons, but the troops seem to avoid meeting one another.

When they begin to mature, males leave their natal troops and move in and out of other troops. Frequent fights break out to determine dominance over access to females or meat. The ranking of these males constantly changes during this period.

Males are accepted into new troops slowly, usually by developing "friendships" with different females around the edge of a troop. They often help to defend a female and her offspring.