Herd

Herd

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Herd refers to a social grouping of certain animals of the same species, either wild
Wildness
Wildness is literally the quality of being wild or untamed, but further to this, it has been defined as a quality produced in nature , as that which emerges from a forest , and as a level of achievement in nature...

 or domestic
Domestication
Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...

, and also to the form of collective animal behavior
Collective animal behavior
Collective animal behavior describes the coordinated behavior of large groups of similar animals and the emergent properties of these groups. Facets of this topic include the costs and benefits of group membership, the transfer of information across the group, the group decision-making process, and...

 associated with this (referred to as herding
Herding
Herding is the act of bringing individual animals together into a group , maintaining the group and moving the group from place to place—or any combination of those. While the layperson uses the term "herding", most individuals involved in the process term it mustering, "working stock" or...

) or as a verb, to herd, to its control by another species such as human
Human
Humans are the only living species in the Homo genus...

s or dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s.

The term herd is generally applied to mammals, and most particularly to the grazing ungulates that classically display this behaviour. 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, in certain instances, for mammals, particularly sheep or goats. A group of quail
Quail
Quail is a collective name for several genera of mid-sized birds generally considered in the order Galliformes. Old World quail are found in the family Phasianidae, while New World quail are found in the family Odontophoridae...

 is often referred to as a covey. Large groups of carnivores
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

 are usually called pack
Pack (canine)
Pack is a social group of conspecific canids. Not all species of canids - notably the red fox - form packs. Pack size and social behaviour within packs varies across species.-Species which exhibit pack behavior:...

s
, and in nature a herd is classically subject to predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

 from pack hunter
Pack hunter
A pack hunter is a predator belonging to the animal kingdom, which has evolved to hunt its prey by working together with other members of its species. Normally, such animals are closely related. The most commonly known pack hunter is the Gray Wolf, the ancestor of all breeds of domesticated dogs...

s.

Special collective nouns may be used for particular taxa (for example a flock of geese, if not in flight, is sometimes called a gaggle
Gaggle
A gaggle is a term of venery for a flock of geese that isn't in flight; in flight, the group can be called a skein.In terms of geese, a gaggle is equal to at least five geese....

) but for theoretical discussions of behavioural ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

, the generic term herd can be used for all such kinds of assemblage.

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. Examples of herds in this sense include shepherd
Shepherd
A shepherd is a person who tends, feeds or guards flocks of sheep.- Origins :Shepherding is one of the oldest occupations, beginning some 6,000 years ago in Asia Minor. Sheep were kept for their milk, meat and especially their wool...

s (who tend to sheep), goatherd
Goatherd
A goatherd or goatherder is a person who herds goats as a vocational activity. Similar to a fisherman who catches fish for a living, the drover here herds goats. Goatherds are popular in countries where goat populations are significant; for instance, in Africa and South Asia...

s (who tend to goats), cowherds (who tend cattle), and others.

Why do animals herd?


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 co-ordination. Rather, each individual is choosing behaviour that corresponds to that of the majority of other members, possibly through imitation or possibly because all are responding to the same external circumstances. A herd can be contrasted with a co-ordinated group where individuals have distinct roles. Many human groupings, such as army detachments or sports teams, show such co-ordination and differentiation of roles, but so do some animal groupings such as those of eusocial insects, which are co-ordinated through pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...

s and other forms of animal communication
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...

.

The question of why animals group together is one of the most fundamental in sociobiology
Sociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...

 and behavioural ecology. As noted above, the term "herd" is most commonly used of grazing animals such as ungulates, and in these cases it is believed that the strongest selective pressure leading to herding rather than a solitary existence is protection against predators. There is clearly a tradeoff involved, since on the one hand a predator may hesitate to attack a large group of animals, while on the other a large group offers an easily detected target. It is generally believed that the most important protective factor is risk dilution - even if a predator attacks the herd, the risk for any individual that it will be the victim is greatly reduced. In the case of predators, it is often unclear whether the term "herd" is appropriate, since there may be some degree of co-ordination or role differentiation in group hunting. Predator groups are commonly smaller than grazing groups, since although a pack may be more effective at pulling down prey than a single animal, the prey then has to be shared between all members, so that the weaker animals will often be better off hunting smaller prey on their own.

The structure and size of herds


A herd is by definition relatively unstructured. However, there may be one or a few animals which tend to be imitated by the rest of the members of the herd more than others. An animal taking this role is called a "control animal", since its behaviour will predict that of the herd as a whole. It cannot be assumed, however, that the control animal is deliberately taking a leadership role. Control animals are not necessarily, or even usually, those that are socially dominant
Dominance hierarchy
A dominance hierarchy is the organization of individuals in a group that occurs when competition for resources leads to aggression...

 in conflict situations, though they frequently are. Group size
Group size measures
Many animals, including humans, tend to live in groups, herds, flocks, bands, packs, shoals, or colonies of conspecific individuals. The size of these groups, as expressed by the number of participant individuals, is an important aspect of their social environment...

 is an important characteristic of the social environment of gregarious species.


Domestic herds


Domestic animal herds are assembled by humans for practicality in raising them and controlling them. Their behaviour may be quite different from that of wild herds of the same or related species, since both their composition (in terms of the distribution of age and sex within the herd) and their history (in terms of when and how the individuals joined the herd) are likely to be very different.

Human parallels


The term herd is also applied metaphorically to human beings in social psychology
Social psychology
Social psychology is the scientific study of how people's thoughts, feelings, and behaviors are influenced by the actual, imagined, or implied presence of others. By this definition, scientific refers to the empirical method of investigation. The terms thoughts, feelings, and behaviors include all...

, with the concept of herd behaviour. However both the term and concepts that underlie its use are controversial.

The term has acquired a semi-technical usage in behavioral finance
Behavioral finance
Behavioral economics and its related area of study, behavioral finance, use social, cognitive and emotional factors in understanding the economic decisions of individuals and institutions performing economic functions, including consumers, borrowers and investors, and their effects on market...

 to describe the largest group of market investor
Investor
An investor is a party that makes an investment into one or more categories of assets --- equity, debt securities, real estate, currency, commodity, derivatives such as put and call options, etc...

s or market speculators who tend to 'move with the market,' or 'follow the general market trend.' This is at least a plausible example of genuine herding, though according to some researchers it results from rational decisions through processes such as information cascade and rational expectations
Rational expectations
Rational expectations is a hypothesis in economics which states that agents' predictions of the future value of economically relevant variables are not systematically wrong in that all errors are random. An alternative formulation is that rational expectations are model-consistent expectations, in...

. Other researchers, however, ascribe it to non-rational process such as mimicry, fear and greed contagion
Emotional contagion
Emotional contagion is the tendency to catch and feel emotions that are similar to and influenced by those of others. One view developed by John Cacioppo of the underlying mechanism is that it represents a tendency to automatically mimic and synchronize facial expressions, vocalizations, postures,...

. "Contrarians" or contrarian investor
Contrarian investing
In finance, a contrarian is one who attempts to profit by investing in a manner that differs from the conventional wisdom, when the consensus opinion appears to be wrong....

s are those who deliberately choose to invest or speculate counter to the "herd".

See also


  • Stampede
    Stampede
    A stampede is an act of mass impulse among herd animals or a crowd of people in which the herd collectively begins running with no clear direction or purpose....

  • Gaggle
    Gaggle
    A gaggle is a term of venery for a flock of geese that isn't in flight; in flight, the group can be called a skein.In terms of geese, a gaggle is equal to at least five geese....

  • Herding
    Herding
    Herding is the act of bringing individual animals together into a group , maintaining the group and moving the group from place to place—or any combination of those. While the layperson uses the term "herding", most individuals involved in the process term it mustering, "working stock" or...

  • Herd behavior
    Herd behavior
    Herd behavior describes how individuals in a group can act together without planned direction. The term pertains to the behavior of animals in herds, flocks and schools, and to human conduct during activities such as stock market bubbles and crashes, street demonstrations, sporting events,...

  • Herder
    Herder
    A herder is a worker who lives a possibly semi-nomadic life, caring for various domestic animals, in places where these animals wander pasture lands....

  • Catalina Island buffalo herd
    Catalina Island buffalo herd
    The non-native but charismatic Catalina Island bison herd has existed for nearly a century.A herd of American Bison roam, supposedly first imported to California's Catalina Island in 1924 for the silent film version of Zane Grey's Western tale, The Vanishing American. Over the decades, the bison...