Costs and Benefits of Female Mate Choice in Pronghorn, Antilocapra americana
It is now clear that females in many animal species do not mate randomly. The behavior of females before mating suggests a sampling process in which the value of potential mates is assessed. Although we now know that female mate choice exists, we do not know what benefits a female gains from choice, or what specific behavioral rules she uses to make choice. The goal of this research is to evaluate evolutionary models that offer answers to these questions. To evaluate the models, it is necessary to measure the energy cost of mate sampling and the effects of choice on offspring quality, and to record how the experiences of females during sampling guide their choice behavior.
This research will take advantage of a well-developed study site (the National Bison Range in northwestern Montana) where individually marked pronghorn may be studied at close range. Each year, most pronghorn females sample potential mates over a two-week period, and then mate once. The energy cost of sampling will be measured using detailed records of female movements during rut, reconstructed from 10-minute interval Global Positioning System locations. Sire effects on offspring performance will be measured by recording prenatal and postnatal growth rates of fawns, as well as size-adjusted body mass and first winter survival. Sire identity will be verified genetically. Information to test hypotheses about the mate sampling method will be obtained by recording the complete sequences of female visits to males and whether, at each visit, the female has had the opportunity to see the male perform vigorously.