Survival and Reproductive Effort in Banner‐Tailed Kangaroo Rats

Nine years of demographic data for two unmanipulated populations of banner—tailed kangaroo rats (Dipodomys spectabilis) in Arizona provide measures of survival, fecundity, age structure, and density. We use these data to search for costs of reproduction in two important components of fitness: survival and future fecundity. We also examine the interaction effects among reproductive effort, age, sex, and density on survival and future fecundity. None of the analyses reveals a significant negative effect of reproductive effort on survival or future fecundity. This result may be seen as evidence that reproduction has no measurable costs in fitness for bannertails. However, another explanation is that bannertails adjust their reproductive effort to individual circumstances so as to minimize costs.