Basic requirements of individual primates include obtaining food, avoiding predators, and reproducing. When these basic requirements are best pursued in the company of others, groups will form. [1] Multi-male groups, also known as multi-male/multi-female, are a type of social organization where the group contains more than one adult male, more than one adult female, and offspring. This structure is characterized by group living (as opposed to solitary), polygynandrous, and strong reproductive competition among males, which could result in an uneven division of male reproductive success (i.e. reproductive skew). [1] [2] [3] There are no stable heterosexual bonds as both males and females have a number of different mates. [4] Multi-male groups are common among semi-terrestrial primates, like savanna baboons, macques, colobus and some New World monkeys.
A factor influencing the number of males in a group may be to avoid predators, as a study found significant positive correlations between the number of males in a group and the predation risk where the group lived. [5] Another study found that there is a significant positive correlation between the number of males per female and the estimated predation rate. [6] This finding may reflect the adaptive advantage to females of tolerating multiple males that provide vigilance and predator defense. [7]
There are two theories about the advantages of multi-male groups against predators: (1) males are more vigilant [7] or (2) males more actively engage in the physical defense of the group's females and immatures. [8]
In multi-male groups, there is typically no single male that has full control over the reproductive share of females. [4] Females in multi-male groups will mate multiple times with different top ranking males as well as lower ranking males and occasionally bachelor "lone wolf" males outside of the group. Most female primates do not have a particular breeding season but can be receptive all year around, however they will most likely not mate if they are already caring for an infant. [9]
Female-female conflicts over reproduction have been overlooked in contrast to male-male competition. [10] Recently, reviews and studies found that while it may not affect mating competition, sexual activity is a primary determinant of female-female aggression and thus female social relationships. [11]
In social systems with promiscuous breeding like multi-male groups, polygamy causes possible ambiguity in parentage. [12] Since kin discrimination between fathers and infants could be more difficult, it has been theorized in the past that the incidence of male care of infants in polygamous primate groups may be less in multi-male groups than in monogamous primate groups. However, in the last five years, this view has changed as a result of careful documentation of intimate male-infant affiliations in certain species, especially in the savanna-dwelling baboons species and barbary macaques. [13] Male paternal care includes: protection from predators, protection from aggression by conspecifics, access to preferred foods, grooming, transport, and adoption. Among other macaques, chimpanzees, and vervet monkeys, male care of young is reports the least. The variation in male paternal care may be due to the differences in the importance of male care to infant survival, the differences in male confidence of paternity, which may relate to seasonal breeding patterns and the presence or absence of conspicuous signs of female ovulation, and the relative costs and benefits of other opportunities available to males (e.g. mating opportunities).
Significant male infanticide has been documented in a number of multi-male societies in two general contexts: when new immigrants rise to the alpha position in the male dominance hierarchy; [14] or when coalitionary cohorts of alien males collectively replace the entire male membership of a group. [15]
In some multi-male groups, the costs for infanticidal males seem likely to be high, since other resident males might defend the victim, and the benefits seem likely to be low because of the generally lower paternal probability in multi-male groups. [16] However, in other primate species living in multi-male groups, males have been observed to kill infants. The aggressors are typically extra-group males, recent immigrants, have recently been introduced or are conceived outside the group, mainly due to the fact that they could not possibly be related to the infants they kill. A male's age and rank influence the occurrence of infanticide. The youngest and highest-ranking immigrant males are more likely to commit infanticide than their older and lower-ranking counterparts if putative fathers fail to protect infants.
A benefit of living in multi-male groups is the collective protection that the group as a whole receives from outsiders as well as sufficient protection of infants against infanticide from other outside roaming males. [17] Another benefit is the low costs of finding a mate and reproducing since the males and females are always together. Also, participants in multi-male groups have better access to resources such as food and living quarters. However, a major cost to living in a multi-male group is the constant competition for mates, mainly among males but also among females.
Most non-human primate communities are more or less closed to contact with members of other communities. [18] Most often, they are tied to a particular locale and rarely migrate outside of their home range. This aloofness from other troops prevents high concentrations of individuals, which could result in rapid depletion of local resources. Communities usually avoid each other and are aggressive towards outsiders. As a result, social interactions between members of different troops are usually very rare, especially for females. Chimpanzees are a notable exception. When chimpanzees from different troops come together, there is often an exciting, friendly encounter lasting several hours, following which, some of the adult females switch groups. Apparently, they are seeking new mates. Occasionally, however, contact between communities of the comparatively unpredictable chimpanzees will develop into genocidal violence. Interactions within non-human primate communities are usually unlimited. Subgroups are rarely closed from group interaction. All members of a community have daily face-to-face, casual interaction. The most common type of subgroup consists of a mother and her young offspring.
Black-and-white colobuses are Old World monkeys of the genus Colobus, native to Africa. They are closely related to the red colobus monkeys of genus Piliocolobus. There are five species of this monkey, and at least eight subspecies. They are generally found in high-density forests where they forage on leaves, flowers and fruit. Social groups of colobus are diverse, varying from group to group. Resident-egalitarian and allomothering relationships have been observed among the female population. Complex behaviours have also been observed in this species, including greeting rituals and varying group sleeping patterns. Colobi play a significant role in seed dispersal.
The gelada, sometimes called the bleeding-heart monkey or the gelada baboon, is a species of Old World monkey found only in the Ethiopian Highlands, living at elevations of 1,800–4,400 m (5,900–14,400 ft) above sea level. It is the only living member of the genus Theropithecus, a name derived from the Greek root words for "beast-ape". Like its close relatives in genus Papio, the baboons, it is largely terrestrial, spending much of its time foraging in grasslands, with grasses comprising up to 90% of its diet.
Semnopithecus is a genus of Old World monkeys native to the Indian subcontinent, with all species with the exception of two being commonly known as gray langurs. Traditionally only the species Semnopithecus entellus was recognized, but since about 2001 additional species have been recognized. The taxonomy has been in flux, but currently eight species are recognized.
The olive baboon, also called the Anubis baboon, is a member of the family Cercopithecidae Old World monkeys. The species is the most wide-ranging of all baboons, being native to 25 countries throughout Africa, extending from Mali eastward to Ethiopia and Tanzania. Isolated populations are also present in some mountainous regions of the Sahara. It inhabits savannahs, steppes, and forests. The common name is derived from its coat colour, which is a shade of green-grey at a distance. A variety of communications, vocal and non-vocal, facilitate a complex social structure.
The chacma baboon, also known as the Cape baboon, is, like all other baboons, from the Old World monkey family. It is one of the largest of all monkeys. Located primarily in southern Africa, the chacma baboon has a wide variety of social behaviours, including a dominance hierarchy, collective foraging, adoption of young by females, and friendship pairings. These behaviors form parts of a complex evolutionary ecology. In general, the species is not threatened, but human population pressure has increased contact between humans and baboons. Hunting, trapping, and accidents kill or remove many baboons from the wild, thereby reducing baboon numbers and disrupting their social structure.
Social grooming is a behavior in which social animals, including humans, clean or maintain one another's bodies or appearances. A related term, allogrooming, indicates social grooming between members of the same species. Grooming is a major social activity and a means by which animals who live in close proximity may bond, reinforce social structures and family links, and build companionship. Social grooming is also used as a means of conflict resolution, maternal behavior, and reconciliation in some species. Mutual grooming typically describes the act of grooming between two individuals, often as a part of social grooming, pair bonding, or a precoital activity.
The sooty mangabey is an Old World monkey found in forests from Senegal in a margin along the coast down to the Ivory Coast.
In animal communication, an alarm signal is an antipredator adaptation in the form of signals emitted by social animals in response to danger. Many primates and birds have elaborate alarm calls for warning conspecifics of approaching predators. For example, the alarm call of the blackbird is a familiar sound in many gardens. Other animals, like fish and insects, may use non-auditory signals, such as chemical messages. Visual signs such as the white tail flashes of many deer have been suggested as alarm signals; they are less likely to be received by conspecifics, so have tended to be treated as a signal to the predator instead.
The wedge-capped capuchin or Guianan weeper capuchin is a capuchin monkey from South America. It is found in northern Brazil, Guyana and Venezuela. Cebus olivaceus is known to dwell in tall, primary forest and travel over long distances during the day.
In ethology, fission–fusion society is one in which the size and composition of the social group change as time passes and animals move throughout the environment; animals merge into a group (fusion)—e.g. sleeping in one place—or split (fission)—e.g. foraging in small groups during the day. For species that live in fission–fusion societies, group composition is a dynamic property. The change in composition, subgroup size, and dispersion of different groups are 3 main elements of a fission-fusion society.
In animals, infanticide involves the intentional killing of young offspring by a mature animal of the same species. Animal infanticide is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. The practice has been observed in many species throughout the animal kingdom, especially primates but including microscopic rotifers, insects, fish, amphibians, birds and mammals. Infanticide can be practiced by both males and females.
Allomothering, allomaternal infant care/handling, or non-maternal infant care/handling is performed by any group member other than the mother. Alloparental care is provided by group members other than the genetic father or the mother and thus is distinguished from parental care. Both are widespread phenomena among social insects, birds and mammals.
Sexual dimorphism describes the morphological, physiological, and behavioral differences between males and females of the same species. Most primates are sexually dimorphic for different biological characteristics, such as body size, canine tooth size, craniofacial structure, skeletal dimensions, pelage color and markings, and vocalization. However, such sex differences are primarily limited to the anthropoid primates; most of the strepsirrhine primates and tarsiers are monomorphic.
One-male groups are a type of social organization where one male interacts with a group of females and their immature offspring. Offspring of both sexes are evicted from the group upon reaching puberty. It can be seen in many species of primates, including the gelada baboon, the patas monkey, savanna baboon, sun-tailed monkey, golden snub-nosed monkey, and the hamadryas baboon. There are costs and benefits for individuals living in one-male groups. As well, individuals within one-male groups can interact with each other just like individuals can interact with those from different one-male groups.
Sexual swelling, sexual skin, or anogenital tumescence refers to localized engorgement of the anus and vulva region of some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swellings; preferring, and competing for, females with the largest swellings.
Social monogamy in mammals is defined as sexually mature adult organisms living in pairs. While there are many definitions of social monogamy, this social organization can be found in invertebrates, reptiles and amphibians, fish, birds, mammals, and humans.
In biology, paternal care is parental investment provided by a male to his own offspring. It is a complex social behaviour in vertebrates associated with animal mating systems, life history traits, and ecology. Paternal care may be provided in concert with the mother or, more rarely, by the male alone.
In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season. Polyandry is often compared to the polygyny system based on the cost and benefits incurred by members of each sex. Polygyny is where one male mates with several females in a breeding season . A common example of polyandrous mating can be found in the field cricket of the invertebrate order Orthoptera. Polyandrous behavior is also prominent in many other insect species, including the red flour beetle, the adzuki bean weevil, and the species of spider Stegodyphus lineatus. Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.
Infanticide in non-human primates occurs when an individual kills its own or another individual's dependent young. Five hypotheses have been proposed to explain infanticide in non-human primates: exploitation, resource competition, parental manipulation, sexual selection, and social pathology.
Primate sociality is an area of primatology that aims to study the interactions between three main elements of a primate social network: the social organisation, the social structure and the mating system. The intersection of these three structures describe the socially complex behaviours and relationships occurring among adult males and females of a particular species. Cohesion and stability of groups are maintained through a confluence of factors, including: kinship, willingness to cooperate, frequency of agonistic behaviour, or varying intensities of dominance structures.
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