Female behavior and reproductive success in a hybrid baboon group (Papio hamadryas hamadryas x Papio hamadryas anubis) (Ethiopia)

In this study, I investigated female social behavior and short-term reproductive success in hybrid baboons (Papio hamadryas anubis x P. h. hamadryas) living in Ethiopia's Awash National Park. The extremely divergent social behaviors of the hamadryas, a harem based, multi-leveled society, and the anubis, a multi-male/multi-female society, lends import to documenting the social behavior and corresponding reproductive output of hybrids. The goals of this study were to (1) investigate the female social organization, mating patterns, and social structure of baboon hybrids; and (2) evaluate the behavioral, hormonal, and genetic correlates of reproductive success. I collected 12 months of behavioral and physiological data from 25 hybrid females living in a group at the center of the hybrid zone, group H. I evaluated the relationships between ancestry and behavior for inter-sexual relationships and intra-sexual relationships. Ancestry for each female was calculated using phenotype (4 taxon-specific traits) and genetics (10 taxon-specific microsatellite loci). I used fecal hormone data on corticosterone and testosterone to evaluate the potential costs associated with behavioral strategies. I estimated the reproductive output for each female using actual birth and survivorship data, maternity analysis, and profiles of ovarian hormones (estradiol and progesterone) that detect instances of reproductive failure.; Group H had an unusual society that reflected elements of both hamadryas and anubis societies. Females varied considerably in levels of bonding to a single male (a hamadryas trait) or bonding to female kin (an anubis trait). Ancestry was correlated with many taxon-specific behaviors indicating the potential for female behavioral differences to structure the hybrid zone. High rank was associated with significant costs including high rates of miscarriage. The characteristics essential to maintaining female rank may carry significant reproductive costs in this hybrid group. Most importantly, females associated with the intermediate behavioral patterns had the lowest measures of reproductive output, while females with more hamadryas ancestry had the highest measures of reproductive output. Thus, hybrid females may be at a behavioral disadvantage, while hamadryas females may have a physiological advantage. Consequently, both social and physiological differences among females may structure gene flow in the Awash hybrid zone.