Reproductive Failure Predicts Intracolony Dispersal of Female Black-Tailed Prairie Dogs (Cynomys ludovicianus) in a Northern Population

Dispersal in mammals is typically male-biased and occurs primarily in sexually immature individuals. These dispersal characteristics are especially true for ground-dwelling sciurids, such as black-tailed prairie dogs (Cynomys ludovicianus), that have polygynous breeding systems, with dispersing males and philopatric females. Prairie dogs are small, colonial rodents found in patches throughout the Great Plains of North America. Previous literature reports that females exist in philopatric units called coteries, typically with one unrelated breeding male. Yearling males disperse from their natal coterie in order to form their own coteries. We observed 1450 prairie dogs over 3 consecutive years in one colony near the northern limit of this species' range, in Grasslands National Park, Saskatchewan. We found that female dispersal occurred at higher rates than previously reported in the literature. We found no difference between the rate of intracolony dispersal for males and females in our study population. Also, we observed that the majority (14/21) of the dispersing females had recently experienced reproductive failure. We suggest that these females dispersed to increase their potential fitness by attempting reproduction in a new territory. This finding is the first instance of a ground-dwelling sciurid demonstrating female-biased breeding dispersal and suggests that factors influencing dispersal are more complicated than previously reported for black-tailed prairie dogs.