In ethology, an aggregation is any form of gathering of organisms and the process of coming together. In some forms groups of unrelated species might form, in which interaction between members of the aggregation might be minimal; for example herds of grazing zebra and antelopes might combine, both the better to observe the approach of predators, and to improve the odds of escape in the event of attack by predators. Sometimes there might be some interaction, such as mixed flocks of birds that observe each other's foraging behaviour in searching for food. Sometimes there might be quite orderly common action, such as the queuing up for a resource; for example different species of fishes may aggregate around a cleaning station where cleaner wrasse and cleaner shrimp are active, more or less taking turns for attention. Such aggregations, where there is no particular association of species or sizes, may be referred to loosely as unstructured aggregations. Commonly they are very temporary and may be loose, with flocks or herds associating casually and separating equally casually within hours.
Structured aggregations tend to be longer-term and of a specific life-cycle function and context. Typically, though not necessarily, they will be of a single species. Often they will be of a single age and possibly of a single sex, such as shoals of fish fry that have specific ecological requirements that are not compatible with those of the mature species. One class of such aggregations comprises groups of adult, but immature "bachelor" males of elephants, seals, lions and other animals in which the mature herd will not tolerate males that would begin to compete with the dominant males. Another is when aposematic larvae of certain insects such as some Lepidoptera and Hemiptera form a flock that feed together and may migrate in "processions" until they are mature after which some kinds disperse. Most species of migrating birds and mammals flock on a large scale, partly for protection and partly for greater reliability of navigation. In some species of Hemiptera the adults remain with their aggregated immature offspring, sometimes in protective roles.
The range of functions is very wide in detail, but among the more important classes of function are security against predators, success in food location, wide range of mate choice, with concomitant increase of outbreeding opportunities, location with other members of the same species (sometimes adherence to separate communities can almost amount to parapatric residence when say, different communities of rats or chimpanzees have violent mutual antipathy). There also are various forms of educational function, such as in some species where the young must learn the correct mate recognition skills, and in highly intelligent species such as crows and elephants, must learn the necessary social skills and the necessary traditional foraging techniques in their region.
Aggregation activities are not restricted to the animal kingdom; for one example, a fundamental class of aggregations occurs in the various groups of slime molds, in which separate cells actually aggregate in the process of constructing their reproductive structure.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae. There are 34 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.
Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. It is a highly interdisciplinary topic. As a term, swarming is applied particularly to insects, but can also be applied to any other entity or animal that exhibits swarm behaviour. The term flocking or murmuration can refer specifically to swarm behaviour in birds, herding to refer to swarm behaviour in tetrapods, and shoaling or schooling to refer to swarm behaviour in fish. Phytoplankton also gather in huge swarms called blooms, although these organisms are algae and are not self-propelled the way animals are. By extension, the term "swarm" is applied also to inanimate entities which exhibit parallel behaviours, as in a robot swarm, an earthquake swarm, or a swarm of stars.
The yellow-headed blackbird is a medium-sized blackbird with a yellow head.
A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called herding. These animals are known as gregarious animals.
Ceratopsidae is a family of ceratopsian dinosaurs including Triceratops, Centrosaurus, and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous. All but one species are known from western North America, which formed the island continent of Laramidia during most of the Late Cretaceous. Ceratopsids are characterized by beaks, rows of shearing teeth in the back of the jaw, elaborate nasal horns, and a thin parietal-squamosal shelf that extends back and up into a frill. The group is divided into two subfamilies—Chasmosaurinae and Centrosaurinae. The chasmosaurines are generally characterized by long, triangular frills and well-developed brow horns. The centrosaurines had well-developed nasal horns or nasal bosses, shorter and more rectangular frills, and elaborate spines on the back of the frill.
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.
The black wildebeest or white-tailed gnu, is one of the two closely related wildebeest species. It is a member of the genus Connochaetes and family Bovidae. It was first described in 1780 by Eberhard August Wilhelm von Zimmermann. The black wildebeest is typically 170–220 cm (67–87 in) in head-and-body length, and the typical weight is 110–180 kg (240–400 lb). Males stand about 111–121 cm (44–48 in) at the shoulder, while the height of the females is 106–116 cm (42–46 in). The black wildebeest is characterised by its white, long, horse-like tail. It also has a dark brown to black coat and long, dark-coloured hair between its forelegs and under its belly.
A mixed-species feeding flock, also termed a mixed-species foraging flock, mixed hunting party or informally bird wave, is a flock of usually insectivorous birds of different species that join each other and move together while foraging. These are different from feeding aggregations, which are congregations of several species of bird at areas of high food availability.
Horse behavior is best understood from the view that horses are prey animals with a well-developed fight-or-flight response. Their first reaction to a threat is often to flee, although sometimes they stand their ground and defend themselves or their offspring in cases where flight is untenable, such as when a foal would be threatened.
Papilio demodocus, the citrus swallowtail or Christmas butterfly, is a swallowtail butterfly which commonly occurs over the entirety of sub-Saharan Africa, including Madagascar, besides the southern Arabian Peninsula. The caterpillars feed on various native plants of especially the family Rutaceae, but have also taken to the leaves of cultivated citrus trees.
Damaliscus lunatus is a large African antelope of the genus Damaliscus and subfamily Alcelaphinae in the family Bovidae, with a number of recognised geographic subspecies. Some authorities have split the different populations of the species into different species, although this is seen as controversial.
The chirruping wedgebill is a medium-sized member of the genus Psophodes, which consists or four to five songbirds endemic to Australia. Commonly found in low shrublands in south-eastern inland Australia, the species is distinguished by its distinctive, chirruping call. The chirruping wedgebill and chiming wedgebill were considered to be a single species until as late as 1973, when they were separated due to marked differences in their calls.
Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding. They include particularly fishes of the order Clupeiformes, but also other small fish, including halfbeaks, silversides, smelt such as capelin and goldband fusiliers.
Collective animal behavior is a form of social behavior involving the coordinated behavior of large groups of similar animals as well as emergent properties of these groups. This can include the costs and benefits of group membership, the transfer of information, decision-making process, locomotion and synchronization of the group. Studying the principles of collective animal behavior has relevance to human engineering problems through the philosophy of biomimetics. For instance, determining the rules by which an individual animal navigates relative to its neighbors in a group can lead to advances in the deployment and control of groups of swimming or flying micro-robots such as UAVs.
In biology, any group of fish that stay together for social reasons are shoaling, and if the group is swimming in the same direction in a coordinated manner, they are schooling. In common usage, the terms are sometimes used rather loosely. About one quarter of fish species shoal all their lives, and about one half shoal for part of their lives.
A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators. Small schooling fish are eaten by many types of predators, and for this reason they are called bait fish or forage fish.
The selfish herd theory states that individuals within a population attempt to reduce their predation risk by putting other conspecifics between themselves and predators. A key element in the theory is the domain of danger, the area of ground in which every point is nearer to a particular individual than to any other individual. Such antipredator behavior inevitably results in aggregations. The theory was proposed by W. D. Hamilton in 1971 to explain the gregarious behavior of a variety of animals. It contrasted the popular hypothesis that evolution of such social behavior was based on mutual benefits to the population.
The eastern cattle egret is a species of heron found in the tropics, subtropics and warm temperate zones. Most taxonomic authorities lump this species and the western cattle egret together as subspecies of the cattle egret, but some separate them. Despite the similarities in plumage to the egrets of the genus Egretta, it is more closely related to the herons of Ardea. It is native to southern and eastern Asia, and Australasia.
Ropalidia plebeiana is a eusocial temperate paper wasp. It is unique, as it is the only temperate wasp in the typically tropical Ropalidia genus. R. plebeiana is widely distributed in eastern Australia, and recently have been found making huge nest aggregations, with thousands of nests on trunks of trees, in south-eastern New South Wales.
In ethology and evolutionary biology, group living is defined as individuals of the same species (conspecifics), maintaining spatial proximity with one another over time with mechanisms of social attraction. Solitary life in animals is considered to be the ancestral state of living; and group living has thus evolved independently in many species of animals. Therefore, species that form groups through social interaction will result in a group of individuals that gain an evolutionary advantage, such as increased protection against predators, access to potential mates, increased foraging efficiency and the access to social information.
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