Harem (zoology)

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Large male northern fur seal and harem of smaller females Callorhinus ursinus and harem.jpg
Large male northern fur seal and harem of smaller females

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.

Contents

For the male, the primary benefit of the harem system is obtaining exclusive access to a group of mature females. The females benefit from being in a stable social group and the associated benefits of grooming, predator avoidance and cooperative defense of territory. The disadvantages for the male are the energetic costs of gaining or defending a harem which may leave him with reduced reproductive success. The females are disadvantaged if their offspring are killed during dominance battles or by incoming males.

Overview

The term harem is used in zoology to distinguish social organization consisting of a group of females, their offspring, and one to two males. [1]

The single male, called the dominant male, may be accompanied by another young male, called a "follower" male. Females that closely associate with the dominant male are called "central females," while females who associate less frequently with the dominant male are called "peripheral females." [2] Juvenile male offspring leave the harem and live either solitarily, or, with other young males in groups known as bachelor herds. [3] Sexually mature female offspring may stay within their natal harem, or may join another harem. [4] The females in a harem may be, but are not exclusively, genetically related. [1] [5] [6] For instance, the females in hamadryas baboon harems are not usually genetically related because their harems are formed by "kidnapping" females from other harems and subsequent herding. [1] In contrast, gelada harems are based on kinship ties to genetically related females. [7] Multiple harems may assemble into larger groups known as "clans" or "teams". [8]

Harem cohesiveness is mediated by the dominant male who fights off invading males to keep claim over the harem. [9] [10] [11] In some harem-forming species, when a dominant male vacates his harem (due to death, defection to another harem, or usurpation) the incoming male sometimes commits infanticide of the offspring. [12] Because time and resources are no longer being devoted to the offspring, infanticide often stimulates the female to return to sexual receptivity and fertility sooner than if the offspring were to survive. Furthermore, while lactating, females do not ovulate and consequently are not fertile. Infanticide therefore has the potential to increase the incoming male's reproductive success. [12] [13]

Benefits

Harems are a beneficial social structure for the dominant male, as it allows him access to several reproductively available females at a time. [10] Harems provide protection for the females within a particular harem, as dominant males will fiercely ward off potential invaders. [11] This level of protection may also, such in the case of the common pheasant, reduce the energy expended by females on remaining alert to, or fleeing from, invading males. [11] Harems allow bonding and socialization among the female members, which can result in greater control over access to females as determined by the females' preferences. Harems also facilitate socialized behavior such as grooming and cooperative defense of territory. [1] [14]

Costs

Harems can prove energetically costly for both males and females. Males spend substantial amounts of energy engaging in battles to invade a harem, or to keep hold of a harem once dominance has been established. [9] Such energy expenditure can result in reduced reproductive success such as in the case of red deer. [9] This is especially true when there is high turnover rates of dominant males, as frequent intense fighting can result in great expenditure of energy. [9] High turnover rate of dominant males can also be energetically costly for the females as their offspring are frequently killed in harems where infanticide occurs. Harems can also negatively affect females if there is intra-harem competition among females for resources. [15]

A lower-cost alternative mating strategy, useful to bachelors without a harem, is kleptogyny (from Greek klepto- "stealing" and -gyny "female"), popularly known as the "sneaky fucker strategy", where a male sneaks in to mate while the harem owner is distracted: in the case of red deer, when the harem stag is involved in a fight with another older stag. [16] [17] The strategy is also recorded in the elephant seal. [18]

Examples

Animals that form harems include:

Mammals

Primates

Birds

Insects

Fish

Explanatory notes

    Related Research Articles

    <i>Phasianus</i> Genus of birds

    The "typical" pheasant genus Phasianus in the family Phasianidae consists of two species. The genus name is Latin for pheasant.

    <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">Dominance hierarchy</span> Type of social hierarchy

    In biology, a dominance hierarchy is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is sometimes called an alpha, and a submissive lower-ranking individual is called a beta. Different types of interactions can result in dominance depending on the species, including ritualized displays of aggression or direct physical violence. In social living groups, members are likely to compete for access to limited resources and mating opportunities. Rather than fighting each time they meet, individuals of the same sex establish a relative rank, with higher-ranking individuals often gaining more access to resources and mates. Based on repetitive interactions, a social order is created that is subject to change each time a dominant animal is challenged by a subordinate one.

    <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">Reproductive suppression</span>

    Reproductive suppression is the prevention or inhibition of reproduction in otherwise healthy adult individuals. It includes delayed sexual maturation (puberty) or inhibition of sexual receptivity, facultatively increased interbirth interval through delayed or inhibited ovulation or spontaneous or induced abortion, abandonment of immature and dependent offspring, mate guarding, selective destruction and worker policing of eggs in some eusocial insects or cooperatively breeding birds, and infanticide, and infanticide in carnivores of the offspring of subordinate females either by directly killing by dominant females or males in mammals or indirectly through the withholding of assistance with infant care in marmosets and some carnivores. The Reproductive Suppression Model argues that "females can optimize their lifetime reproductive success by suppressing reproduction when future conditions for the survival of offspring are likely to be greatly improved over present ones”. When intragroup competition is high it may be beneficial to suppress the reproduction of others, and for subordinate females to suppress their own reproduction until a later time when social competition is reduced. This leads to reproductive skew within a social group, with some individuals having more offspring than others. The cost of reproductive suppression to the individual is lowest at the earliest stages of a reproductive event and reproductive suppression is often easiest to induce at the pre-ovulatory or earliest stages of pregnancy in mammals, and greatest after a birth. Therefore, neuroendocrine cues for assessing reproductive success should evolve to be reliable at early stages in the ovulatory cycle. Reproductive suppression occurs in its most extreme form in eusocial insects such as termites, hornets and bees and the mammalian naked mole rat which depend on a complex division of labor within the group for survival and in which specific genes, epigenetics and other factors are known to determine whether individuals will permanently be unable to breed or able to reach reproductive maturity under particular social conditions, and cooperatively breeding fish, birds and mammals in which a breeding pair depends on helpers whose reproduction is suppressed for the survival of their own offspring. In eusocial and cooperatively breeding animals most non-reproducing helpers engage in kin selection, enhancing their own inclusive fitness by ensuring the survival of offspring they are closely related to. Wolf packs suppress subordinate breeding.

    <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.

    <span class="mw-page-title-main">Sexual dimorphism in non-human primates</span>

    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.

    <span class="mw-page-title-main">Baboon</span> Genus of mammals

    Baboons are primates comprising the genus Papio, one of the 23 genera of Old World monkeys, in the family Cercopithecidae. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow baboon, the Kinda baboon and the chacma baboon. Each species is native to one of six areas of Africa and the hamadryas baboon is also native to part of the Arabian Peninsula. Baboons are among the largest non-hominoid primates and have existed for at least two million years.

    <span class="mw-page-title-main">One-male group</span>

    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.

    Polygyny is a mating system in which one male lives and mates with multiple females but each female only mates with a single male. Systems where several females mate with several males are defined either as promiscuity or polygynandry. Lek mating is frequently regarded as a form of polygyny, because one male mates with many females, but lek-based mating systems differ in that the male has no attachment to the females with whom he mates, and that mating females lack attachment to one another.

    <span class="mw-page-title-main">Sexual swelling</span> Swelling of genital and perineal skin in some mammals as a sign of fertility

    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.

    <span class="mw-page-title-main">Sexual selection in mammals</span> Mode of natural selection

    Sexual selection in mammals is a process the study of which started with Charles Darwin's observations concerning sexual selection, including sexual selection in humans, and in other mammals, consisting of male–male competition and mate choice that mold the development of future phenotypes in a population for a given species.

    Sexual coercion among animals is the use of violence, threats, harassment, and other tactics to help them forcefully copulate. Such behavior has been compared to sexual assault, including rape, among 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.

    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.

    <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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