Density‐Related Changes in Survival of Philopatric and Dispersing Kangaroo Rats

Seven years of mark—recapture data from a population of banner—tailed kangaroo rats (Dipodomys spectabilis) revealed lower survival of dispersing juveniles at high population density than at low density. Acquisition of the maternal burrow and food caches provided survival advantages of high density but not at low density. These differences were significant in both sexes, but they were more pronounced in females. A previous report found shorter dispersal distances at higher density. The present study shows that this pattern was due partially to a tendency to move less at high density, especially in males, and partially to lowered survival to maturity of individuals that dispersed at high density, especially in females. These results support the hypothesis that dispersing animals' chances of successful recruitment are inversely related to density, and that high—density saturated conditions favor philopatry over dispersal. Moreover, this effect of saturation on the advantages and frequency of philopatry was greater in females, the sex that is usually philopatric in mammals.