The two systems of social organization of equines

This organization is that of domestic horses, Przewalski’s horses, plains zebras, moutain zebras and Mongolian khulan (subspecies of Asian wild ass)

Equines are organized into families (harems), in which a male (rarely several) associates himself to a few mares with their foals of less than 2-3 years old. This structure is relatively stable. Young males leave their native group and live in small groups of single males from the age of 2 to 5 years old, these groups also include males who have lost their harems.

These equines are not territorial ^[1]. the Home range^[2] of these different groups overlap more or less extensively (1 to few km²). There is no active defense of certain areas of the home range.

This system (stable social links) is suited to areas where food resources are relatively abundant, or at least evenly distributed. In case of seasonal alternation of food resources, these species can gather to migrate temporarily, as a whole group, towards more favorable sites. This fusion-fission system is observable in plains zebras with a migration of a lot of individuals.

But depending on ressources, it has been observed, in some very specific cases, emergence of territorial systems in some population of feral^[3]  horses with few ressources.

^[1] territory = part of the home range that is defended
^[2]home range = Space where the animal usually lives and which is sufficient to meet its primary needs
^[3]feral or brown horses = domestic horses returned to the wild

Concerned equines

This organization is that of  wild African donkeys, Grevy’s zebras and certain species of Asian donkeys (Tibetan donkeys « kiang » and certain hemions (« khur » in India, « khulan » in Turkmenistan-Kazakhstan, onagers in Iran)). The latter present a certain variability in their social structure.

This system is completly different from the first one. There are no stable relationships between individuals, apart from the mare and her offspring. They can remain either solitary or find themselves in temporary associations of various compositions, of one or of both sexe(s). Males defend very large breeding areas (10km²) only when a female in season is present. Only the male of the territory can cover the females there. He can tolerate other males if they are not interested in the females in season. He will only leave his territory in case of extreme drought and will come back as soon as possible.

Domestic donkeys are descendants of African wild donkeys. During the breeding season and especially in presence of females in season, domestic donkeys (reproductive male donkeys) are territorial. They can easily attack other males.

This system (few territorial males, looser links) where individuals are more solitary is adapted to life in desert-like areas, with very limited and unevenly distributed ressources.

But depending on resources available to these species, it has been observed an inversion between these two systems of social organizations ; fairly stable group of donkeys (especially between jennies (female donkeys) and their males), in particular when food is abundant. In hemions, we can observe one or the other of the systems of social organizations depending on the subspecies studied. For feral donkeys^[3], resources and topography of the habitat may condition composition of female groups, and reproductive strategy of males could be related to the distribution of females in the habitat and their visibility.

Concerned equines