Abstract # 98:

Scheduled for Friday, June 22, 2012 11:45 AM-12:00 PM: Session 14 (Magnolia) Oral Presentation


I. Godoy and S. E. Perry
University of California - Los Angeles, Department of Anthropology, Center for Behavior, Evolution, and Culture, Los Angeles, California 90024, USA
     Selection is assumed to lead to reproductive seasonality if the timing of births impacts the likelihood of infant or maternal survival. At Lomas Barbudal, 78% of births (164 of 210) have occurred during the 6-month period of February through July, with 52% of births concentrated into the 3-month period of May, June, and July. Similar results from neighboring Santa Rosa (Carnegie et al., 2011), suggest that moderate birth seasonality is a characteristic feature across capuchin populations. We use demographic data from Lomas Barbudal on births and deaths documented from 1990 through 2011 (N=179 births) to test the hypotheses that births are concentrated into months that (1) give the highest survival probability to infants (measured directly through mortality rates) or (2) give the highest survival probability to mothers (measured indirectly through interbirth intervals as a proxy for maternal condition). Infants born during peak months had mortality rates (N=121, mortality rate=0.29) that did not differ significantly (chi2, p=0.241) from that of infants born during non-peak months (N=58, mortality rate=0.21). Females that gave birth during peak months had significantly shorter interbirth intervals (N=58, mean=755.2 days) than females that gave birth during off-peak months (N=24, mean=819 days) (p=0.0175, two-sample t-test with equal variances). Data support the hypothesis that females time births in order to maximize their own survival prospects.