Mortality Associated with Sheep Operations in Idaho

Abstract

Nine sheep bands from Idaho were monitored for mortality causes and circumstances during 1973 and 1974; two bands were monitored during 1975. Total ewe and lamb losses for the respective years were 9.5%, 11.5%, and 11.1%. Premature births, starvation, and disease were major causes of lamb deaths during the 3-month home ranch lambing period. During the same period, disease, shearing stress, infection, and birth complications were the main causes of ewe mortality. The yearly mean total loss for lambs on the range was 5.2%, the minimum (confirmed) loss to predators was 1.4%, and other known causes of death represented 1.1% loss. The mean minimum predation was adjusted to 2.9% on the basis of unaccounted for loss. The minimum predation rate on ewes was 1.1% (adjusted 1.6%) even though they were on the range twice as long as lambs. Coyotes accounted for 93% of all predator-killed lambs and ewes. Predation was most severe on lambs during the first 6 weeks on the range, but more ewes were killed during the fall and winter.