COST-BENEFIT ANALYSIS OF ALLOGROOMING BEHAVIOUR IN CERCOCEBUS TORQUATUS LUNULATUS

Abstract We assume that allogrooming is an activity which yields various benefits to the participants and at the same time its practice requires a resource investment. In this work we aim to quantify the costs and benefits derived for each subject by performing allogrooming in order to find the maximum net benefit gained and the equilibrium point above which a major allogrooming investment would not increase the benefits obtained. The data were obtained observing the members of a captive troop (N = 9) of white crowned mangabeys (Cercocebus torquatus lunulatus) at the Barcelona Zoo. Allogrooming time and the preceding and following context were recorded for each actor. The costs were quantified as the energetic expenditure required to perform allogrooming as proposed by Coelho (1974). The benefits were estimated from the frequency and duration of bouts associated to transitions preceded by an agonistic context and followed by a neutral context. The equilibrium values of time spent in allogrooming, for which the costs equalled the benefits, and the value for time invested corresponding to maximal net benefits, were estimated from the theoretical model adjusted to the data. It was found that the differences between the equilibrium point and the maximal net benefit were correlated with the age of the subject, which can be understood as an effect of learning the relation cost-benefit of allogrooming to maintain low levels of agonism within the troop.