Mass and fat influence the timing of natal dispersal in Belding's ground squirrels

We examined influences of body mass and content of body fat on the timing of natal-dispersal behavior in juvenile male Belding's ground squirrels (Spermophilus beldingi). We manipulated body mass and body fat of juveniles by provisioning them with food and we used unprovisioned juveniles as controls. We evaluated the percentage of body mass composed of fat in juvenile males, using the non-destructive method of measuring electrical conductivity of the body. Our results suggest that natal dispersal in this species is constrained by the energetic demands of depositing fat for hibernation. Our results further indicate that juvenile male S. beldingi postpone dispersal until they have attained a threshold body mass, and that the percentage of body mass composed of fat may importantly influence the timing of dispersal behavior.