Allonursing in white-faced capuchins (Cebus capucinus) provides evidence for cooperative care of infants

Abstract

Allonursing is a highly cooperative behaviour that may have important fitness consequences for the infant while the benefits to the allomother are less clear. To investigate the function of this behaviour, we compared patterns of allonursing and nursing exhibited by white-faced capuchin monkeys (Cebus capucinus). We used a linear mixed model approach to analyse data collected on 21 infants from six social groups in Sector Santa Rosa, Costa Rica. Infants nursed at higher rates and for longer durations from their mothers than from allonurses. They also allonursed at higher rates from lactating and non-lactating parous females than from nulliparous females and at higher rates from maternally related female allonurses than other females. We found no observed effect of adult female rank or infant sex. We conclude that infant white-faced capuchins engage in allonursing as a means to acquire additional milk, and that participating allonurses may benefit from increased inclusive fitness.