Reproduction, Mortality, and Female Reproductive Success in Chacma Baboons of the Okavango Delta, Botswana

Abstract

Predation, food competition, and infanticide all negatively impact female reproductive success. Female dominance rank may mitigate these effects, if competitive exclusion allows high-ranking females to gain priority of access to critical food resources. It may also exacerbate them, if low-ranking females are forced to feed or rest in marginal habitats where they are at increased risk. In this chapter, we present data on reproduction, mortality, and female reproductive success from a 10-year study of free-ranging chacma baboons (Papio hamadryas ursinus) in the Okavango Delta of Botswana and examine the influence of predation, infanticide, and dominance rank on female reproductive success. Predation appeared to be the cause of most deaths among adult females and juveniles, whereas infanticide was the most likely cause of deaths among infants. Seasonality strongly affected both births and mortality: The majority of conceptions occurred during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-month period when flooding was at its peak, most likely because the group was more constrained to move along predictable routes during this time. Those reproductive parameters most likely to be associated with superior competitive ability-interbirth interval and infant growth rates-conferred a slight fitness advantage on high-ranking females. This fitness advantage was counterbalanced, however, by the effects of infanticide and predation. Infanticide affected high- and low-ranking females more than middle-ranking females, while predation affected females of all ranks relatively equally. As a result, there were few rank-related differences in estimated female lifetime reproductive success.