When making foraging decisions, female primates may follow specific behavioral strategies that reflect their reproductive state. Lactation is considered the most energetically costly phase for females, but we argue that gestation is also energetically expensive for squirrel monkeys. In this study, we examined whether female squirrel monkeys (a seasonally breeding primate) in different reproductive phases showed significant differences in their foraging ecology. We sampled two wild groups of squirrel monkeys (Saimiri collinsi) using the focal animal method, during 12 months (June 2014 to May 2015). During this time, we quantified the effect of reproductive state (mating, gestation, and lactation) and sex (females vs. males) on activity budgets, foraging efficiency, dietary composition, and nearest neighbors. We found significant effects of both sex and reproductive phase on the mean proportion of time spent foraging, resting, traveling, and being social. Females consumed more insects than did males at all times; among females, time spent eating prey and fruit varied according to reproductive state. These data suggest that, due to their life history and seasonal breeding, reproduction is a costly activity for female Saimiri, and not only during lactation. Therefore, adopting the appropriate behavioral strategies is essential to reduce energetic deficits in females.

Many mammals coincide their reproductive activities with factors such as ambient temperature, rainfall and food availability. In primates that invest immediate food intake into reproduction, the periods of maximum fruit production often coincide with the peak of lactation (to maximize maternal survival) or the occurrence of weaning (to maximize infant survival). This study investigates the relationship between reproductive periods and the availability of ripe fruit in the habitat of a population of wild squirrel monkeys (Saimiri collinsi) in Amazonian

Squirrel monkeys (Saimiri collinsi) are seasonal breeders that live in large social groups in which females are dominant to males. Females have one infant per year, and the nursing period lasts six to eight months. Preliminary observations in the wild indicated that during the mating period (eight weeks: July and August in our population), the infants show agonism directed at males who approach their mothers. This directed sexual interference by infants has rarely been reported for neotropical primates. Our study reports observations in a natural population of Saimiri collinsi with the aim of describing the social behavior of infants during the breeding season, especially with regard to adult males in the group. Infants of both sexes were observed during three mating periods (2011, 2012, 2013), to test hypotheses about the possible function of infant harassment directed at adult males. The behavior of infants (variables: activity and nearest neighbor) was sampled by the focal animal method as well as ad libitum observations. We recorded 99 cases of agonism and 17 cases of tolerance between nearby males and infants via the all-occurrence method. Thus, 85% of interactions between adult males and infants involved agonism. These results suggest that infant interference can present a cost to adult males during the breeding season.