One-male group

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Gelada Baboon Male Gelada Baboon male.jpg
Gelada Baboon Male
Hamadryas Baboon Male Hamadryas baboon male.jpg
Hamadryas Baboon Male

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, [1] the patas monkey, savanna baboon, [2] sun-tailed monkey, golden snub-nosed monkey, and the hamadryas baboon. [3] There are costs and benefits for individuals living in one-male groups. [4] [5] As well, individuals within one-male groups can interact with each other just like individuals can interact with those from different one-male groups. [1] [6]

Contents

Origin

A study of savanna baboons (hamadryas ursinus) indicates that the one-male groups in this species are formed by fissioning. [2] For example, a 100-month old male entered a multi male - multi female (mm) group then formed a one-male group with eight of the adult females in the MM group. Juveniles of the species, suspected to be young of the eight adult females, also joined the new one-male group. [2] However, when a new male successfully enters a one-male group, the social hierarchy will be changed depending on the previously determined rankings of the newly entered male. The previous resident male of the one-male group may be out-ranked and therefore placed lower on the hierarchy of males. [2]

Costs

Infanticide

One of the costs of living in one-male groups is the killing of unweaned young by conspecific adult males. This is known as infanticide, and mostly occurs when adult males or coalitions of males takeover the group and kill the resident male. [4] This is done to increase the reproductive success of the intervening males because the females are more likely to mate with them now that they need to produce new offspring. While the infanticide is an obvious cost to females, it is beneficial to the infanticidal males. Infanticide in one-male groups has been studied in the Virungas population of mountain gorillas. [4]

Inbreeding

Another cost of living in one-male social groups is that there is a high occurrence of inbreeding. This means that closely related individuals can mate and produce offspring. This results in decreasing genetic diversity with subsequent generations of the species. For example, inbreeding has been studied in one-male groups of sun-tailed monkeys (Cercopithecus solatus ). [7] In this study, the time between two births for females increased when an inbred offspring was born. This suggests that there could be increased maternal costs with giving birth to and rearing an inbred offspring, compared to a noninbred offspring. [7] Inbreeding depression resulted from the decreased genetic diversity within this population, meaning that the population as a whole experienced a decrease in fitness (i.e. reproductive success). Unlike infanticide, the high occurrence of inbreeding in one-male groups is a disadvantageous to both the females and males in the group. [7]

Benefits

Feeding advantages

Experiments involving the hamadryas baboon species ( hamadryas hamadryas ) provide evidence of feeding advantages for male and female members of one-male groups. However, the findings of feeding advantages were only evident when these one-male groups formed clans. [5] It has been shown that males from single one-male groups did not approach males that were part of clans to compete for food sources. Additionally, it was found that males from smaller clans did not approach males from bigger clans (i.e. with more one-male groups) to compete for food. Ultimately, these feeding advantages of decreased competition were seen between one-male groups, not for males within the same groups or clans. [5] In addition, it can be said that males and females in a clan have feeding advantages compared to males and females in single one-male groups because it has been shown that the males and females in clans gain access to clumped food sources earlier than those in single one-male groups and that they spend more time with clumped food sources than the single groups. [5]

Within-group interactions

Female-female interactions

Studies of social interactions among golden snub‐nosed monkeys ( Rhinopithecus roxellana ) reveal that adult females tend to interact with each other, but they do not form strong social bonds with other females in the same one-male group. [1]

Female-male interactions

It has been shown that adult female golden snub-nosed monkeys do not form strong social relationships with the resident male in the one-male group. [1] However, the adult females tended to interact more with other adult females instead of the resident male when they were looking for social interaction. [1]

Patterns of social relationships

While researchers have found that individuals in one-male groups of hamadryas baboons exhibit a pattern of social relationships called a star-shaped relationship, it has been found that gelada baboon ( Theropithecus gelada ) individuals in one-male groups exhibit a net-shaped relationship pattern. [1] Individuals in the snub-nosed monkey species exhibit a different pattern of social relationships than the two other baboon species. [1]

Between-group interactions

Allomaternal nursing

In a study of social relationships among a clan (i.e. multiple one-male groups) of Yunnan snub-nosed monkeys ( Rhinopithecus bieti ), it was determined that the adult females of one-male groups sometimes care for the young of other one-male groups. [6] For example, when a mother and her young offspring were accidentally separated, a mother belonging to a different one-male group cared for the young. The separated young was nursed by the adoptive mother (who also nursed her own offspring) and tolerated by the resident male of the one-male group that the offspring was now temporarily a part of. [6]

Affiliative interactions

Affiliative interactions between individuals of one-male groups include sitting near, grooming in front of, and handling the infants of other one-male groups. [8] The most prevalent type of affiliative interaction seen in a study involving Sichuan snub-nosed monkeys (Rhinopithecus roxellana) is infant handling. [8] This infant handling can form gatherings of multiple one-male units that forage together. This type of social structure is called a band. [8]

See also

Related Research Articles

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Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae. Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons, red colobus and macaques. Common names for other Old World monkeys include the talapoin, guenon, colobus, douc, vervet, gelada, mangabey, langur, mandrill, surili (Presbytis), patas, and proboscis monkey. Phylogenetically, they are more closely related to apes than to New World monkeys. They diverged from a common ancestor of New World monkeys around 45 to 55 million years ago.

<span class="mw-page-title-main">Gelada</span> Species of Old World monkey

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.

<span class="mw-page-title-main">Olive baboon</span> Also called the Anubis baboon, is a member of the family Cercopithecidae (Old World monkeys)

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.

<span class="mw-page-title-main">Hamadryas baboon</span> Species of baboon

The hamadryas baboon is a species of baboon within the Old World monkey family. It is the northernmost of all the baboons, being native to the Horn of Africa and the southwestern region of the Arabian Peninsula. These regions provide habitats with the advantage for this species of fewer natural predators than central or southern Africa where other baboons reside. The hamadryas baboon was a sacred animal to the ancient Egyptians and appears in various roles in ancient Egyptian religion, hence its alternative name of 'sacred baboon'.

<span class="mw-page-title-main">Guinea baboon</span> Species of Old World monkey

The Guinea baboon is a baboon from the Old World monkey family. Some (older) classifications list only two species in the genus Papio, this one and the hamadryas baboon. In those classifications, all other Papio species are considered subspecies of P. papio and the species is called the savanna baboon.

<span class="mw-page-title-main">Chacma baboon</span> Species of baboon from the Old World monkey family

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.

<span class="mw-page-title-main">Snub-nosed monkey</span> Genus of mammals

Snub-nosed monkeys are a group of Old World monkeys and make up the entirety of the genus Rhinopithecus. The genus is rare and not fully researched. Some taxonomists group snub-nosed monkeys together with the genus Pygathrix.

<span class="mw-page-title-main">Harem (zoology)</span> Animal group consisting of one or two males, a number of females and their offspring

A harem is an animal group consisting of one or two males, a number of females, and their offspring. The dominant male drives off other males and maintains the unity of the group. If present, the second male is subservient to the dominant male. As juvenile males grow, they leave the group and roam as solitary individuals or join bachelor herds. Females in the group may be inter-related. The dominant male mates with the females as they become sexually active and drives off competitors, until he is displaced by another male. In some species, incoming males that achieve dominant status may commit infanticide.

<span class="mw-page-title-main">Wedge-capped capuchin</span> Species of New World monkey

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<span class="mw-page-title-main">Infanticide (zoology)</span> Killing of young offspring by an adult animal of the same species

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.

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<span class="mw-page-title-main">Gray snub-nosed monkey</span> Species of Old World monkey

The gray snub-nosed monkey, also known as Brelich's snub-nosed monkey, Guizhou snub-nosed monkey, and Guizhou golden monkey, is a species of primate in the family Cercopithecidae. It is endemic to China, where it is known as the Guizhou golden hair monkey (黔金丝猴) or gray golden hair monkey (灰金丝猴). It is threatened by habitat loss. Of the three species of snub-nosed monkeys in China, the gray snub-nosed monkey is the most threatened, with a total population thought to number fewer than 400 individuals.

<span class="mw-page-title-main">Golden snub-nosed monkey</span> Species of Old World monkey

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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. 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, polygynandrous, and strong reproductive competition among males, which could result in an uneven division of male reproductive success. There are no stable heterosexual bonds as both males and females have a number of different mates. Multi-male groups are common among semi-terrestrial primates, like savanna baboons, macques, colobus and some New World monkeys.

<span class="mw-page-title-main">Myanmar snub-nosed monkey</span> Species of Old World monkey

The Myanmar snub-nosed monkey or Burmese snub-nosed monkey or black snub-nosed monkey is a critically endangered species of colobine monkey discovered in 2010 in northern Burma (Myanmar). It was formally described as a novel species of primate in 2011 based on its fur, beard and tail. Two groups of the species were discovered in China in 2011 and 2015, respectively.

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<span class="mw-page-title-main">Primate sociality</span>

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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