The impact of alpha male replacements on reproductive seasonality and synchrony in white‐faced capuchins (Cebus imitator)

Abstract

Objectives: Reproductive seasonality is typically associated with ecological factors, but it can also be related to social factors, such as alpha male replacements (AMR). Such events can produce distinct birth peaks outside of the ecological peak, poten- tially increasing hardship for mother and infant and ultimately reducing fitness. We examined the impact of AMRs on birth seasonality, birth synchrony, and infant sur- vival in the Santa Rosa population of white-faced capuchins (Cebus imitator). Materials and Methods: We analyzed 33 years of data on seven capuchin groups to test whether AMRs and births occur seasonally and whether birth seasonality changes following AMRs. Using sliding window analysis, we tested whether ecologi- cal conditions predict births in future months. We also tested whether birth period affects infant survival and likelihood of infanticide. Results: AMRs shift birth seasonality from the ecological birth peak in the early wet season (late May–July) to a social birth peak during the late dry season (March–May), but they do not affect synchrony. In addition, we found that being born in the social peak significantly decreases infant survival relative to individuals born in the ecologi- cal and nonpeak periods. Discussion: These findings suggest that Santa Rosa's predictable seasons can provide conception cues for female capuchins, but AMRs disrupt this ecological timing of conceptions. We suggest the increased infant mortality associated with the social birth peak is related to seasonal factors, including water scarcity and varying resource availability, and increased risk of infanticide, as the social birth peak overlaps with the AMR peak