Social systems Richard Wrangham stated that
social systems of primates are best classified by the amount of movement by females occurring between groups. He proposed four categories: • Female transfer systems – females move away from the group in which they were born. Females of a group will not be closely related whereas males will have remained with their natal groups, and this close association may be influential in social behavior. The groups formed are generally quite small. Evidence of this social system (called
patrilocal residence when used by the
Anthropology) has also been found among
Neanderthal remains in
Spain and in remains of
Australopithecus and
Paranthropus robustus groups in southern Africa. Among New World Monkeys,
spider monkeys and
muriquis use this system. s. The two individuals on the right exposing their white ventral surface are sunning themselves. • Male transfer systems – while the females remain in their natal groups, the males will emigrate as adolescents. Group sizes are usually larger. Some prosimians,
colobine monkeys and
callitrichid monkeys also use this system. An analysis of breeding records of captive primate colonies representing numerous different species indicates that the infant mortality of inbred young is generally higher than that of non-inbred young. This effect of inbreeding on infant mortality is probably largely a result of increased expression of deleterious recessive alleles (see
Inbreeding depression). s are social great apes. Primatologist
Jane Goodall, who studied in the
Gombe Stream National Park, noted
fission-fusion societies in chimpanzees. There is
fission when the main group splits up to forage during the day, then
fusion when the group returns at night to sleep as a group. This social structure can also be observed in the
hamadryas baboon,
spider monkeys These social systems are affected by three main ecological factors: distribution of resources,
group size, and
predation. Within a social group there is a balance between cooperation and competition. Cooperative behaviors in many primates species include
social grooming (removing
skin parasites and cleaning wounds), food sharing, and collective defense against predators or of a territory. Aggressive behaviors often signal competition for food, sleeping sites or mates. Aggression is also used in establishing
dominance hierarchies. In November 2023, scientists reported, for the first time, evidence that groups of primates, particularly
bonobos, are capable of cooperating with each other. Among the predators of these monkeys is the
common chimpanzee. The
red-tailed monkey associates with several species, including the western red colobus,
blue monkey,
Wolf's mona monkey,
mantled guereza,
black crested mangabey and
Allen's swamp monkey. In South America,
squirrel monkeys associate with
capuchin monkeys. This may have more to do with foraging benefits to the squirrel monkeys than anti-predation benefits. Polygynous species include gorillas,
Hanuman langurs, geladas, hamadryas baboons,
proboscis monkeys, and
golden snub-nosed monkeys, where one male mates with multiple females within a
harem or one-male unit. Sexual dimorphism tends to be higher in these species and males may also develop prominent
secondary sex characteristics. In the patriarchal hamadryas baboon, the males aggressively herd females into their groups and violently discipline those that wander. By contrast, in gelada society, which is based on female kinship, a male is dependent on the support of the females in his unit and cannot impose on them. Polygynous males must defend their harems from rivals, who may try to take over. Most modern human societies consist of monogamous
marriages, but allow for polygyny, particularly for those of a high status. Such behavior play an important role in bonobo society in particular. female bonobos engage in mutual genital-rubbing behavior, possibly to bond socially with each other, thus forming a female nucleus of bonobo society. The bonding among females enables them to dominate most of the males.
Life history breastfeeding her baby|thumb Primates have slower rates of development than other mammals. All primate infants are
breastfed by their mothers (with the exception of some human cultures and various zoo raised primates which are fed formula) and rely on them for grooming and transportation. In some species, infants are protected and transported by males in the group, particularly males who may be their fathers. Other relatives of the infant, such as siblings and aunts, may participate in its care as well. Most primate mothers cease
ovulation while breastfeeding an infant; once the infant is
weaned the mother can reproduce again. This often leads to weaning conflict with infants who attempt to continue breastfeeding. Polygynandry may also lessen the risk of infanticide since paternity becomes uncertain. Some primates such as
galagos and
New World monkeys use tree-holes for
nesting, and park juveniles in leafy patches while foraging. Other primates follow a strategy of "riding", i.e. carrying individuals on the body while feeding. Adults may construct or use nesting sites, sometimes accompanied by juveniles, for the purpose of resting, a behavior which has developed secondarily in the great apes. During the juvenile period, primates are more susceptible than adults to
predation and
starvation; they gain experience in feeding and avoiding predators during this time. Late in life, female catarrhine primates appear to undergo a cessation of reproductive function known as
menopause; other groups are less studied.
Diet and feeding Primates exploit a variety of food sources. It has been said that many characteristics of modern primates, including humans, derive from an early ancestor's practice of taking most of its food from the tropical canopy. Most primates include fruit in their diets to obtain easily digested nutrients including
carbohydrates and
lipids for energy. Many primates have anatomical specializations that enable them to exploit particular foods, such as fruit, leaves, gum or
insects. Some species have additional specializations. For example, the
grey-cheeked mangabey has thick
enamel on its teeth, enabling it to open hard fruits and seeds that other monkeys cannot.
Hunting Tarsiers are the only
extant obligate carnivorous primates, exclusively eating insects, crustaceans, small vertebrates and snakes (including
venomous species).
Capuchin monkeys can exploit many different types of plant matter, including fruit, leaves, flowers, buds, nectar and seeds, but also eat insects and other
invertebrates, bird eggs, and small vertebrates such as birds,
lizards,
squirrels and
bats. The meat consumption includes predation on other primate species, such as the
western red colobus monkey. and
invertebrates. In some instances, bonobos have been shown to consume lower-order primates. Until the development of agriculture approximately 10,000 years ago,
Homo sapiens employed a hunter-gatherer method as their sole means of food collection. This involved combining stationary food sources (such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks) with
wild game, which must be hunted and killed in order to be consumed. It has been proposed that humans have used fire to prepare and
cook food since the time of
Homo erectus. Around ten thousand years ago,
humans developed agriculture, which substantially altered their diet. This change in diet may also have altered human biology; with the spread of
dairy farming providing a new and rich source of food, leading to the evolution of the ability to digest
lactose in some adults.
As prey Predators of primates include various species of
carnivorans,
birds of prey,
reptiles, and other primates. Even gorillas have been recorded as prey. Predators of primates have diverse hunting strategies and as such, primates have evolved several different
antipredator adaptations including
crypsis,
alarm calls and
mobbing. Several species have separate alarm calls for different predators such as air-borne or ground-dwelling predators. Predation may have shaped group size in primates as species exposed to higher predation pressures appear to live in larger groups.
Communication vocalizing
Lemurs,
lorises,
tarsiers, and New World monkeys rely on
olfactory signals for many aspects of social and reproductive behavior. Primates also use vocalizations, gestures, and facial expressions to convey psychological state. Hand and arm gestures are also important forms of communication for great apes and a single gesture can have multiple functions. Chest-beating in male gorillas is a form of visual and non-vocal sound communication that serves to show fitness to both rivals and females. Primates are a particularly vocal group of mammals. The
Philippine tarsier, has a high-frequency limit of auditory sensitivity of approximately 91 kHz with a dominant frequency of 70 kHz, among the highest recorded for any terrestrial mammal. For Philippine tarsiers, these ultrasonic vocalizations might represent a private channel of communication that subverts detection by predators, prey and competitors, enhances energetic efficiency, or improves detection against low-frequency background noise. Male
howler monkeys are among the loudest land mammals as their roars can be heard up to , and relate to intergroup spacing, territorial protection and possibly mate-guarding. Male and female
siamangs both possess inflatable pouches in the throat with which pair -bonds use to sing "duets" to each other. The
vervet monkey gives a distinct alarm call for each of at least four different predators, and the reactions of other monkeys vary according to the call. Furthermore, many primate species including
chimpanzees,
Campbell's mona monkeys or
Diana monkeys have been shown to combine vocalizations in sequences, suggesting
syntax may not be uniquely humans as previously thought but rather evolutionary ancient, and its origins may be deeply rooted in the primate lineage. Consonant- and vowel-like sounds exist in some orangutan calls and they maintain their meaning over great distances. The time range for the evolution of human language and/or its anatomical prerequisites extends, at least in principle, from the phylogenetic divergence of
Homo (2.3 to 2.4 million years ago) from
Pan (5 to 6 million years ago) to the emergence of full
behavioral modernity some 50,000–150,000 years ago. Few dispute that
Australopithecus probably lacked vocal communication significantly more sophisticated than that of
great apes in general.
Intelligence and cognition Primates have advanced cognitive abilities: some make tools and use them to acquire food and for social displays; some can perform tasks requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception; they can recognise
kin and
conspecifics; and they can learn to use symbols and understand aspects of human language including some relational syntax and concepts of number and numerical sequence. Research in primate cognition explores problem solving, memory, social interaction, a
theory of mind, and numerical, spatial, and abstract concepts. Comparative studies show a trend towards higher intelligence going from prosimians to New World monkeys to Old World monkeys, and significantly higher average cognitive abilities in the great apes. However, there is a great deal of variation in each group (e.g., among New World monkeys, both
spider There are more limited reports of the closely related
bonobo using tools in the wild; it has been claimed they rarely use tools in the wild although they use tools as readily as chimpanzees when in captivity. It has been reported that females, both chimpanzee and bonobo, use tools more avidly than males.
Orangutans in
Borneo scoop catfish out of small ponds. Over two years, anthropologist Anne Russon observed orangutans learning to jab sticks at catfish to scare them out of the ponds and in to their waiting hands. There are few reports of
gorillas using tools in the wild. An adult female
western lowland gorilla used a branch as a walking stick apparently to test water depth and to aid her in crossing a pool of water. Another adult female used a detached trunk from a small shrub as a stabilizer during food gathering, and another used a log as a bridge. Soon after her initial discovery of tool use, Goodall observed other chimpanzees picking up leafy twigs, stripping off the leaves and using the stems to fish for insects. This change of a leafy twig into a tool was a major discovery. Prior to this, scientists thought that only humans manufactured and used tools, and that this ability was what separated humans from other animals. Sumatran orangutans have been observed making and using tools. They will break off a tree branch that is about 30 cm long, snap off the twigs, fray one end and then use the stick to dig in tree holes for termites. In the wild, mandrills have been observed to clean their ears with modified tools. Scientists filmed a large male mandrill at
Chester Zoo (UK) stripping down a twig, apparently to make it narrower, and then using the modified stick to scrape dirt from underneath its toenails. Captive gorillas have made a variety of tools. The first direct observation of a non-ape primate using a tool in a wild environment occurred in 1988. Primatologist Sue Boinski watched an adult male white-faced capuchin beat a
fer-de-lance snake to death with a dead branch. The black-striped capuchin was the first non-ape primate for which routine tool use was documented in the wild; individuals were observed
cracking nuts by placing them on a stone anvil and hitting them with another large stone. In Thailand and Myanmar,
crab-eating macaques use stone tools to open nuts, oysters and other bivalves, and various types of sea snails. Chacma baboons use stones as weapons; stoning by these baboons is done from the rocky walls of the canyon where they sleep and retreat to when they are threatened. Stones are lifted with one hand and dropped over the side whereupon they tumble down the side of the cliff or fall directly to the canyon floor. Although they have not been observed to use tools in the wild, lemurs in controlled settings have been shown to be capable of understanding the functional properties of the objects they had been trained to use as tools, performing as well as tool-using haplorhines. ==Ecology==