Reproduction in yearling female Columbian ground squirrels (Spermophilus columbianus)

Abstract

In 1980, 4 of 13 yearling female Columbian ground squirrels in a colony in southwestern Alberta raised litters. Mean litter size was not significantly smaller than that of adult females. Breeding and nonbreeding yearling females had similar growth rates as juveniles in 1979, but the former had a lower weight gain in 1980 before their young were weaned. Breeding yearling females were more aggressive and played less than nonbreeders. A combination of apparently good habitat quality in the study area and favourable weather conditions during summer of 1979 and in May of 1980 may have produced early sexual development of these females.