In studies of social animals, the highest ranking individual is sometimes designated as the alpha. Males, females, or both, can be alphas, depending on the species. Where one male and one female fulfill this role together, they are sometimes referred to as the alpha pair. Other animals in the same social group may exhibit deference or other species-specific subordinate behaviours towards the alpha or alphas.
Alpha animals usually gain preferential access to food and other desirable items or activities, though the extent of this varies widely between species. Male or female alphas may gain preferential access to sex or mates; in some species, only alphas or an alpha pair reproduce.
Alphas may achieve their status by superior physical strength and aggression, or through social efforts and building alliances within the group, or more often, simply by breeding and being the parent of all in their pack.
Beta and omega
Social animals in a hierarchical community are sometimes assigned ranks in ethology studies.
Beta animals often act as second-in-command to the reigning alpha or alphas and will act as new alpha animals if an alpha dies or is otherwise no longer considered an alpha. In some species of birds, males pair up in twos when courting, the beta male aiding the alpha male. It has been found that the social context of the animals has a significant impact on courtship behavior and the overall reproductive success of that animal.
Omega (usually rendered ω) is an antonym used to refer to the lowest caste of the hierarchical society. Omega animals are subordinate to all others in the community, and are expected by others in the group to remain submissive to everyone. Omega animals may also be used as communal scapegoats or outlets for frustration, or given the lowest priority when distributing food.
Common chimpanzees use strength, intelligence, and political alliances to establish and maintain alpha position. Alpha males who solely use intimidation and aggression to keep their position often provoke dissent. Coalitions will eventually form, which at some point will topple the alpha male. There have been rare cases where a group has killed the alpha male. Common chimpanzees show deference to the alpha of the community by ritualized postures and gestures such as presenting their back, crouching, bowing, or bobbing. Chimpanzees lower in rank than the alpha male will offer their hand while grunting to the alpha male as a sign of submission. Bonobo society on the other hand is governed by alpha females. Males will associate with females for rank acquisition because females dominate the social environment. If a male is to achieve alpha status in a bonobo group, he must be accepted by the alpha female. Female bonobos use homosexual sex to increase social status. High-ranking females rarely interact sexually with other females, but low-ranking females interact sexually with all females.
Gorillas use intimidation to establish and maintain alpha position. A study conducted regarding the reproductive behavior of male mountain gorillas (Gorilla beringei beringei) found further evidence that dominant males are favored to father offspring, even when there is a greater number of males in a notably enlarged group size. The study also concluded that mating access dropped off less steeply with status; alpha, beta, and gamma showing more similar mating success, compared to what had been previously thought.
A study on the association of alpha males and females during the non-breeding season in wild Capuchin monkeys (Cebus apella nigritus) examined whether alpha males are the preferred mate for females and, secondly, whether female-alpha status and relationship to the alpha-male can be explained through the individual characteristics and or social network of the female. The results indicated that alpha male Capuchin are the preferred mate for adult females. However, only the alpha females had strong interactions with the alpha males by virtue of a dominance hierarchy among the females in which only the most dominant and strong females were able to interact with the alpha male.
In the past, the prevailing view on grey wolf packs was that they consisted of individuals vying with each other for dominance, with dominant grey wolves being referred to as the "alpha" male and female, and the subordinates as "beta" and "omega" wolves. This terminology was first used in 1947 by Rudolf Schenkel of the University of Basel, who based his findings on researching the behaviour of captive grey wolves. This view on gray wolf pack dynamics was later popularized by the researcher L. David Mech in his 1970 book The Wolf. He later found additional evidence that the concept of an Alpha male may have been an erroneous interpretation of incomplete data and formally disavowed this terminology in 1999. He explained that it was heavily based on the behavior of captive packs consisting of unrelated individuals, an error reflecting the once prevailing view that wild pack formation occurred in winter among independent grey wolves. Later research on wild gray wolves revealed that the pack is usually a family consisting of a breeding pair and their offspring of the previous 1–3 years. In the article, Mech wrote that the use of the term "alpha" to describe the breeding pair adds no additional information, and is "no more appropriate than referring to a human parent or a doe deer as an alpha." He further notes the terminology falsely implies a "force-based dominance hierarchy." In 13 years of summer observations of wild wolves, he witnessed no dominance contests between them.
In some other wild canids, the alpha male may not have exclusive access to the alpha female. Other pack members as in the African painted dog (Lycaon pictus) may guard the maternity den used by the alpha female.
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