Sex Differences in Captive Olive Baboon Behavior During the First Fourteen Days of Life

Abstract

I discuss newborn baboon behavioral and proximity sex differences in a population of captive olive baboons (Papio anubis) living in a social group of >500 individuals. The data are based upon 20-min focal observations of 42 mother-newborn pairs (n = 27, n = 15) for infant-days 1–7 and 36 pairs (n = 23, n = 13) for infant-days 8–14 collected late-May through late-November 2001. I examined the first two weeks of infant life via behavioral, proximity, and approach-leave/contact analyses in order to determine whether behavioral sex differences exist during the first few days of life. I examine and analyze these 2 weeks independently due to different sample sizes. I used data from the total available sample population of 57 infants (n = 36, n = 21) to discuss birth, survivorship, and infant weight. Statistically significant age and/or age-sex interactions exist for all of the behavior and proximity measures during either infant-week 1 or 2. Moreover, there is a statistically significant difference in the birth sex ratio in the sample population but no significant difference in infant mortality by sex. There are also relative and significant differences in mothers' treatment of their newborn males and females. There are also some general tendencies for female newborns on average to suckle less and to explore more per focal observation than male infants do as they age. Conversely, male newborns average slightly more time per focal observation 1 m from the mother than do female infants. However, the observed differences may be influenced by maternal behavior in that mothers have higher rates of contact with their female than their male infants.