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| Sources of variance in female mating rate in the Amboseli baboons |
| Austen Ehrie1, Susan Alberts2, Courtney Fitzpatrick1. 1Department of Biology, Texas A&M University, College Station, Texas, United States; 2Department of Biology and Evolutionary Anthropology, Duke University, Durham, North Carolina, United States |
In most species with internal fertilization, females copulate only when their eggs are ready for fertilization. This pattern makes sense in light of the costs associated with copulation (e.g. reduced foraging time, disease transfer, harassment, etc.). However, in some anthropoid primates, females cycle repeatedly and mate often before becoming pregnant. One possible explanation for non-conceptive cycling and mating is that, in systems where males are under strong selection to copulate frequently, the ejaculate supply is constrained. Consequently, females may end up being sperm-limited. Such a scenario would produce competition among females for copulations, producing a positive relationship between the frequency of copulations (i.e. “mating rate”) and the probability of conception. Two critical first steps toward testing this hypothesis are to characterize the sources of variance in female mating rate and to determine whether mating rate predicts conception probability. Here we do the first of these; we leverage behavioral, demographic, and reproductive data from the Amboseli Baboon Research Project to determine the sources of variance in female mating rate. |