Survival of male bighorn sheep in southwestern Alberta

Festa-Bianchet, M.

doi:10.2307/3801344

I monitored the surival of 86 tagged adult male bighorn sheep (Ovis canadensis) in southwestern Alberta from 1981 to 1988. Yearly mortality averaged 33% for yearlings and 18% for 2-year-olds; 7 of 16 deaths in these age classes occurred during a pneumonia epizootic. Yearling male were more likely to die during the epizootic than yearling females. Overwinter survival of male lambs varied among years and was lower after the epizootic than before it. Hunting accounted for 68% of the 28 deaths of males .gtoreq. 5 years old. Natural mortality of males .gtoreq. 3 years old averaged 10% yearly. The mortality of young males was higher than reported by studies based on skull collections. Skull collections may provide a biased estimate of natural mortality. The assumption of high survival of young males may not always be correct.