Dominance hierarchies occur in many social animals.
Dominance hierarchies occur in many social animals.
Researcher M. W. Foster investigated primates and found that the leaders were more likely to be those who did more for those around them instead of being determined by strength. [1]
Alpha male baboons monopolize resources and mating access to females, and they are also more likely to suffer from stress. [2] Lower status males must expend more time and energy for mating opportunities. Alpha males may sometimes allow subordinate males to have access to mating, so the subordinate males can serve as "spare dads" and protect their offspring from other alpha males. [3]
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. [4] 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. [4]
Common chimpanzees use strength, intelligence, and political alliances to establish and maintain alpha position. [5] There have been rare cases where a group has killed the alpha male. [6] [7] Common chimpanzees show deference to the alpha of the community by ritualized postures and gestures such as presenting their back, crouching, bowing, or bobbing. [8] [ verification needed ] Chimpanzees lower in rank than the alpha male will offer their hand while grunting to the alpha male as a sign of submission. [9] 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. [10] 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. [11]
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, so that non-dominant males had mating success more similar to the alpha male than had been expected. [12]
Adult male mandrills with alpha status display vivid coloration on their skin, while those with beta status are more dull in colour. Both types of males engage in mating, but only the dominant alpha males have the ability to produce offspring. Male mandrills sometimes fight for breeding rights which results in dominance. Though conflicts are rare, they can be deadly. Gaining dominance, that is becoming the alpha male, results in an "increased testicular volume, reddening of sexual skin on the face and genitalia, and heightened secretion of the sternal cutaneous gland". [13] When a male loses dominance or its alpha status, the reverse happens, although the blue ridges remain brightened. There is also a fall in its reproductive success. This effect is gradual and takes place over a few years. [14] [15] [16] When beta males mate-guard a female, the competition between them allows the alpha males to have a greater chance of producing offspring, [17] since betas outnumber alphas 21 to 1.
Dominant male elephant seals arrive at potential breeding sites in spring, and fast to ensure that they can mate with as many females as possible. [18] Male elephant seals use fighting, vocal noises, and different positions to determine who will be deemed the dominant male. [18] [19] When males reach eight to nine years of age, they have developed a pronounced long nose, in addition to a chest shield, which is thickened skin in their chest area. [18] They display their dominance by showing their noses, making loud vocalisations, and altering their postures. [18] [19] They fight each other by raising themselves and ramming each other with their chests and teeth. [18]
When females arrive, the dominating males have already selected their territory on the beach. [18] Females cluster in groups called harems, which could consist of up to 50 females surrounding one alpha male. [18] Outside of these groups, a beta bull is normally roaming around on the beach. [18] The beta bull helps the alpha by preventing other males accessing the females. [18] In return, the beta bull might have an opportunity to mate with one of the females while the alpha is occupied. [18]
In the past, the prevailing view on gray wolf packs was that they consisted of individuals vying with each other for dominance, with dominant gray 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 behavior of captive gray wolves. [20] 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 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 gray 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. [21]
In some other wild canids, the alpha male may not have exclusive access to the alpha female. [22] Other pack members as in the African painted dog (Lycaon pictus) may guard the maternity den used by the alpha female. [23]
Male Chiroxiphia manakins can typically be designated alpha and beta, since there is a clear dominance relationship between them. There is only ever one alpha male, but, depending on species, there may be one or two beta males. Beta males are sometimes sub-adults - easily recognized, as their plumage retain female-like characters. Only the alpha male is ever seen to mate with the female. [24]
Webster et al. observed that males defend sexually-receptive females, suggesting that Montezuma oropendolas have a female-defence mating system. While the females nest, the males fight and fend off one another, and the males were ranked depending on the outcome of each fight. The alpha male eventually pushes out all other males until he is the only one left. When the alpha males leave the others come back and defend females until he returns. This type of mating system is similar to that of polygynous mammals, not birds. [25]
Normally, female pale chanting goshawks mate with a single male (monogamy), but in "broken veld" vegetation (a prey-rich habitat in the Little Karoo), a female and two males may form a polyandrous trio. [26] In these cases an alpha male and female will be assisted in raising the young by a beta male. The alpha male copulates with the female 31-5 days before laying while the beta male copulates 5-3 days before laying. [27] Subordinate co-breeding males may have reproductive fitness benefits by assisting the alpha female with nest defense and prey provision. [28] Non-breeding individuals from previous broods may remain in their natal territory and form part of the breeding group. [26]
Aggressive behavior in cichlids is ritualized and consists of multiple displays used to seek confrontation while being involved in evaluation of competitors, [29] coinciding with temporal proximity to mating. Displays of ritualized aggression in cichlids include a remarkably rapid change in coloration, during which a successfully dominant [29] territorial male assumes a more vivid and brighter coloration, while a subordinate or "nonterritorial" male assumes a dull-pale coloration. [30] In addition to color displays, cichlids employ their lateral lines to sense movements of water around their opponents to evaluate the competing male for physical traits/fitness. [31] Male cichlids are very territorial due to the pressure of reproduction, and establish their territory and social status by physically driving out [32] challenging males (novel intruders) [33] through lateral displays (parallel orientation, uncovering gills), [34] biting, or mouth fights (head-on collisions of open mouths, measuring jaw sizes, and biting each other's jaws). The cichlid social dichotomy is composed of a single dominant with multiple subordinates, where the physical aggression of males becomes a contest for resources [32] (mates, territory, food). Female cichlids prefer to mate with a successfully alpha male with vivid coloration, whose territory has food readily available.
Some moon wrasses live in groups consisted of a dominant male, and a "harem" of about a dozen other wrasses, some female and some male. [35] The alpha male is more brightly colored, and at every low tide hour, changes from green to blue, and goes into a show of attacking and nipping all the other wrasses. This is his way of showing his dominance to the rest of the males and keeping the females in check. During breeding season and before high tide, the alpha male turns completely blue, gathers up every single female, and the spawning frenzy begins.
Mozambique tilapias often travel in groups where a strict dominance hierarchy is maintained. Positions within the hierarchy correlate with territoriality, courtship rate, nest size, aggression, and hormone production. [36] In terms of social structure, Mozambique tilapias engage in a system known as lek-breeding, where males establish territories with dominance hierarchies while females travel between them. Social hierarchies typically develop because of competition for limited resources including food, territories, or mates. During the breeding season, males cluster around certain territory, forming a dense aggregation in shallow water. [37] This aggregation forms the basis of the lek through which the females preferentially choose their mates. Reproductive success by males within the lek is highly correlated to social status and dominance. [38]
In experiments with captive tilapias, evidence demonstrates the formation of linear hierarchies where the alpha male participates in significantly more agonistic interactions. Thus, males that are higher ranked initiate much more aggressive acts than subordinate males. However, contrary to popular belief, Mozambique tilapias display more agonistic interactions towards fish that are farther apart in the hierarchy scale than they do towards individuals closer in rank. One hypothesis behind this action rests with the fact that aggressive actions are costly. In this context, members of this social system tend to avoid confrontations with neighboring ranks in order to conserve resources rather than engage in an unclear and risky fight. Instead, dominant individuals seek to bully subordinate tilapias both for an easy fight and to keep their rank. [39]
The bonobo, also historically called the pygmy chimpanzee, is an endangered great ape and one of the two species making up the genus Pan. While bonobos are, today, recognized as a distinct species in their own right, they were initially thought to be a subspecies of Pan troglodytes, due to the physical similarities between the two species. Taxonomically, members of the chimpanzee/bonobo subtribe Panina—composed entirely by the genus Pan—are collectively termed panins.
Cichlids are fish from the family Cichlidae in the order Cichliformes. Traditionally Cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Tanzania during the Eocene epoch, about 46–45 million years ago; however, molecular clock estimates have placed the family's origin as far back as 67 million years ago, during the late Cretaceous period. The closest living relative of cichlids is probably the convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. This family is large, diverse, and widely dispersed. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.
The genus Pan consists of two extant species: the chimpanzee and the bonobo. Taxonomically, these two ape species are collectively termed panins. The two species were formerly collectively called "chimpanzees" or "chimps"; if bonobos were recognized as a separate group at all, they were referred to as "pygmy" or "gracile chimpanzees". Together with humans, gorillas, and orangutans they are part of the family Hominidae. Native to sub-Saharan Africa, chimpanzees and bonobos are currently both found in the Congo jungle, while only the chimpanzee is also found further north in West Africa. Both species are listed as endangered on the IUCN Red List of Threatened Species, and in 2017 the Convention on Migratory Species selected the chimpanzee for special protection.
The mandrill is a large Old World monkey native to west central Africa. It is one of the most colorful mammals in the world, with red and blue skin on its face and posterior. The species is sexually dimorphic, as males have a larger body, longer canine teeth and brighter coloring. It is the largest monkey in the world. Its closest living relative is the drill, with which it shares the genus Mandrillus. Both species were traditionally thought to be baboons, but further evidence has shown that they are more closely related to white-eyelid mangabeys.
Mandrillus is a genus of large Old World monkeys distributed throughout central and southern Africa, consisting of two species: M. sphinx and M. leucophaeus, the mandrill and drill, respectively. Mandrillus, originally placed under the genus Papio as a type of baboon, is closely related to the genus Cercocebus. They are characterised by their large builds, elongated snouts with furrows on each side, and stub tails. Both species occupy the west central region of Africa and live primarily on the ground. They are frugivores, consuming both meat and plants, with a preference for plants. M. sphinx is classified as vulnerable and M. leucophaeus as endangered on the IUCN Red List of Threatened Species.
In the zoological field of ethology, 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.
A pack is a social group of conspecific canines. The number of members in a pack and their social behavior varies from species to species. Social structure is very important in a pack. Canine packs are led by a breeding pair, consisting of the alpha male and alpha female.
The Nile tilapia is a species of tilapia, a cichlid fish native to parts of Africa and the Levant, particularly Israel and Lebanon. Numerous introduced populations exist outside its natural range. It is also commercially known as mango fish, nilotica, or boulti.
Reproductive suppression is the prevention or inhibition of reproduction in otherwise healthy adult individuals. It occurs in birds, mammals, and social insects. It is sometimes accompanied by cooperative breeding. It is maintained by behavioral mechanisms such as aggression, and physiological mechanisms such as pheromone signalling. In evolutionary terms, it may be explained by the theory of inclusive fitness.
The European paper wasp is one of the most common and well-known species of social wasps in the genus Polistes. Its diet is more diverse than those of most Polistes species—many genera of insects versus mainly caterpillars in other Polistes—giving it superior survivability compared to other wasp species during a shortage of resources.
The Mozambique tilapia is an oreochromine cichlid fish native to southeastern Africa. Dull colored, the Mozambique tilapia often lives up to a decade in its native habitats. It is a popular fish for aquaculture. Due to human introductions, it is now found in many tropical and subtropical habitats around the globe, where it can become an invasive species because of its robust nature. These same features make it a good species for aquaculture because it readily adapts to new situations. It is known as black tilapia in Colombia and as blue kurper in South Africa.
Astatotilapia burtoni is a species of fish in the family Cichlidae.
Neolamprologus pulcher is a species of cichlid endemic to Lake Tanganyika where it prefers locations with plenty of sedimentation. The common names for N. pulcher include daffodil cichlid, fairy cichlid, princess of Zambia and lyretail cichlid. This species can reach a length of 10 centimetres (3.9 in) TL. It can also be found in the aquarium trade.
Demonic Males: Apes and the Origins of Human Violence is a 1996 book by Richard Wrangham and Dale Peterson examining the evolutionary factors leading to human male violence.
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.
The challenge hypothesis outlines the dynamic relationship between testosterone and aggression in mating contexts. It proposes that testosterone promotes aggression when it would be beneficial for reproduction, such as mate guarding, or strategies designed to prevent the encroachment of intrasexual rivals. The positive correlation between reproductive aggression and testosterone levels is seen to be strongest during times of social instability. The challenge hypothesis predicts that seasonal patterns in testosterone levels are a function of mating system, paternal care, and male-male aggression in seasonal breeders.
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.
Polyandry in fishes is a mating system where females mate with multiple males within one mating season. This type of mating exists in a variety of animal species. Polyandry has been found in both oviparous and viviparous bony fishes and sharks. General examples of polyandry occur in fish species, such as green swordtails and Trinidadian guppies. Specific types of polyandry have also been classified, such as classical polyandry in pipefish cooperative polyandry in cichlids and convenience polyandry in sharks.
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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