Variation in Maternal Effort, Activity Budgets, and Feeding Behavior in Wild Saddleback Tamarins (<i>Leontocebus weddelli</i>) in Northwestern Bolivia

Among primates, maternal infant care may vary in response to several factors including litter size, reproductive history, and health status. In cooperative breeders, maternal investment may also depend on the amount of help their group mates (or allomothers) provide. We studied infant care and activity in four wild groups of saddleback tamarins (Leontocebus weddelli) and collected hair and fecal samples from which we extracted genomic DNA to estimate kin relationships among group members. We use these data to examine how maternal care was affected by seven factors: a) number of adults; b) number of adult males; c) presence of genetically identified sire; d) number of non-parental close relatives; e) number of infants; f) maternal body mass; and g) maternal parity. Furthermore, to investigate how mothers coped with the costs of reproduction, we compared mothers to other adults in their feeding and resting rates during the 15-weeks pre- and post-partum. Overall, we found that mothers contributed on average 16% of infant transport and 30% of infant food transfers per group-week. We found no significant effects of any of the variables we examined on the proportion of time mothers transported infants or provisioned food. However, mothers rested less than other group members during both the pre- and post-partum periods. Our results demonstrate that all mothers engage in low levels of infant care relative to species without cooperative breeding; however, we failed to find a clear explanation for variation in maternal care among individuals.