Testing Reprodutive Tradeoffs and Fitness Measures in Female Columbian ground squirrels (Urocitellus columbianus)

Abstract

Life history theory is a branch of ecology whose goal is to understand how animals optimize their survival and reproductive success. Under natural conditions, resources are finite and life history traits are subject to trade-offs and other types of constraints. The costs of reproduction are one of the most significant components underlying life-history trade-offs. In order to test for reproductive trade-offs we examined how female Columbian ground squirrels (Urocitellus columbianus) allocated resources to somatic and reproductive efforts. Furthermore, natural selection cannot maximize life history traits and thus fitness. Interpretation of selection of life history traits varies when using different measures of fitness as such, we examined the influence of age at reproductive maturity using two fitness measures, lambda and LRS (lifetime reproductive success). By studying life history traits (i.e age at reproductively maturity) through a variety of theoretical and empirical methods, a combination of traits that maximizes fitness can be determined and used to predict the evolution of major life history traits.