Seasonality of Births in Bighorn Sheep

Abstract

Two populations of bighorn sheep (Ovis canadensis) in contrasting habitats at the same latitude were studied for 3 years to examine effects of climate and nutrition on seasonality of births. The number of births peaked during February and March in the Mojave Desert and during mid-June in the Rocky Mountains. Yearly differences in seasons of birth were apparent in the Mojave Desert, but not in the Rocky Mountains. Comparisons with captive and transplanted populations revealed that desert subspecies of bighorn sheep gave birth earlier in the year and had longer seasons of birth than northern subspecies. Bighorn sheep appear to give birth when temperature and nutrition are most conducive to survival of offspring.