A herd is a term generally applied to the social groups of larger herbivores mammals such as deer, buffaloes and elephants. In addition to them, we have troops of monkeys, surrenders of pigs, packs of wolves, and prides of lions and so on. But the term “herd” applies to all social groups of animals.

A variety of mammals occur in social groups for various reasons. They find it more convenient to move long distances in groups for safety reasons because they can exploit some resource more effectively as a group an because they can defend some resources better as a group against their competitors.

During the rainy season a good number of elephants move in to the Bandipur Tiger Reserve. During the day, they graze in herds of ten to twenty, at noon, near tanks, whereas a hundred elephants may be seen together. Again the same animals form large herds to move from one area to another. It is seasonal migration.

Elephants certainly find safety in numbers, to safeguard their calves. The bulls often live and wander by themselves, but the females in such a group are always vigilant about the calves.

At the slightest alarm the cows rush together to form a protective front for the calves. A very different kind of social group that finds safety in numbers is that of smaller deer and antelopes, such as chital and blackbuck.

Herbivores of this size cannot defend themselves in times of danger. The species that live in forested habitats such as barking deer and four horned antelope are largely asocial. But species that live in more open habitats cannot hide themselves behind shrubs and trees, so they hide themselves behind each other.

Mammals come together to feed themselves more effectively. This is the case with chimpanzees whose groups have no definite territory.

They call each other on discovering good sources of food. The carnivores that hunt into packs such as wild dogs cooperate even more effectively in bringing down victims larger than themselves.

Finally they may form bands to defend a territory over which they feed. They come together against other groups of the same species. The spotted hyena in Africa is known to do this. Even monkeys such as Hanuman Langur do this. At Mount Abu, Hanumans Langur females fight with females of neighboring troops at territorial boundaries and find definite strength in numbers.