Dominance Hierarchy - Mechanisms That Regulate The Formation of Hierarchies in Animals

Mechanisms That Regulate The Formation of Hierarchies in Animals

The most basic interaction that establishes a Dominance Hierarchy is the dyad, or paired interaction among individuals. To study the formation of hierarchies, scientists have often used the dyadic method, in which two individuals are forced to interact isolated from others. All individuals in the group are paired with each other (i.e. a round-robin), in isolation, until a hierarchy can be deduced. The process of deducing the hierarchy involves the construction of a dominance matrix, in which wins/ties are expressed in relation to each member of the group.

Recently, it has been postulated that paired interactions alone cannot account for the emergence of dominance hierarchies. This is because in nature, such paired interactions rarely occur in isolation. Thus, a relatively new concept has now emerged in animal behavior: the study of socially embedded dyads. Such phenomena as the audience effect, the context-dependent audience effect in Betta fish (Betta splendens), the observer effect, and the winner-loser effect, may play important roles in the formation of dominance hierarchies in social groups. Furthermore, it has been argued that the social group forms a complex signaling network: interactions that occur among just two individuals of the group are in turn affected by other signals transmitted by individuals in direct communication with them. In many animals, these putative signals can include postural changes, as well as changes in “state” (such as color changes).

Individuals with greater hierarchical status tend to displace those ranked lower from access to space, to food and to mating opportunities. Thus, individuals with higher social status tend to have greater reproductive success by mating more often and having more resources to invest in the survival of offspring. Hence it serves as an intrinsic factor for population control, insuring adequate resources for the dominant individuals and thus preventing widespread starvation. Territorial behavior enhances this effect.

These hierarchies are not fixed and depend on any number of changing factors, among them are age, gender, body size, intelligence, and aggressiveness.For instance, in linear hierarchies the top ranked individual (“alpha”) is usually replaced by its direct subordinate (“beta”), that assume its role in the group and gain the same benefits. In eusocial species, decrease of fertility is among the main reasons for ranking displacement.