![]() ![]() Whenever groups, such as shoals of fish, synchronize their movements, it becomes harder for predators to focus on particular individuals. Thus, the net effect for an individual in a group concerning its predation risk is beneficial. Greater group sizes result in higher visibility and detection rates for predators, but this relation is not directly proportional and saturates at some point, while the risk of being attacked for an individual is directly proportional to group size. Although the dilution effect is influenced by so-called selfish herding, it is primarily a direct effect of group size instead of the position within a herd. The key argument is that the risk of being preyed upon for any particular individual is smaller within a larger group, strictly due to the fact that a predator has to decide which individual to attack. Perhaps the most studied effect of herds is the so-called dilution effect. ![]() The following includes an outline about some of the major effects determining the trade-offs for living in groups. Thus, animals form groups whenever this increases their fitness compared to living in solitary. Living in groups evolved independently multiple times in various taxa and can only occur if its benefits outweigh the costs within an evolutionary timescale. Theoretical framework is focused on the costs and benefits associated with living in groups in terms of the fitness of each individual compared to living solitarily. Understanding the social behaviour of animals and the formation of groups has been a fundamental goal in the field of sociobiology and behavioural ecology. The reason why animals form herds can not always be stated easily, since the underlying mechanisms are diverse and complex. Traffic jam created by a herd of cattle in Addis Ababa, Ethiopia. Group size is an important characteristic of the social environment of gregarious species.Ĭosts and benefits of animals in groups It cannot be assumed, however, that the control animal is deliberately taking a leadership role control animals are not necessarily socially dominant in conflict situations, though they often are. An animal in this role is called a "control animal", since its behaviour will predict that of the herd as a whole. However, there may be two or a few animals which tend to be imitated by the bulk of the herd more than others. Many human groupings, such as army detachments or sports teams, show such coordination and differentiation of roles, but so do some animal groupings such as those of eusocial insects, which are coordinated through pheromones and other forms of animal communication.Ī herd is, by definition, relatively unstructured. A herd can be contrasted with a coordinated group where individuals have distinct roles. Rather, each individual is choosing behaviour in correspondence with most other members, possibly through imitation or possibly because all are responding to the same external circumstances. When an association of animals (or, by extension, people) is described as a herd, the implication is that the group tends to act together (for example, all moving in the same direction at a given time), but that this does not occur as a result of planning or coordination. Overgrazing is not caused by nomadic grazers in huge populations of travel herds, nor by holistic planned grazing. Wildebeest in Masai Mara during the Great Migration. Examples of herds in this sense include shepherds (who tend to sheep), goatherds (who tend to goats), and cowherds (who tend to cattle). The word herd, as a noun, can also refer to one who controls, possesses and has care for such groups of animals when they are domesticated. Special collective nouns may be used for particular taxa (for example a flock of geese, if not in flight, is sometimes called a gaggle) but for theoretical discussions of behavioural ecology, the generic term herd can be used for all such kinds of assemblage. Large groups of carnivores are usually called packs, and in nature a herd is classically subject to predation from pack hunters. ![]() Different terms are used for similar groupings in other species in the case of birds, for example, the word is flocking, but flock may also be used for mammals, particularly sheep or goats. The term herd is generally applied to mammals, and most particularly to the grazing ungulates that classically display this behaviour. These animals are known as gregarious animals. The form of collective animal behavior associated with this is called herding. Wildebeest at the Ngorongoro Crater an example of a herd in the wildĪ herd is a social group of certain animals of the same species, either wild or domestic. ![]()
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