Sheep Losses on Selected Ranches in Southern Wyoming

Abstract

To help resolve conflicting claims about the severity of predator losses to the sheep industry, sheep losses from all causes were assessed during 1973-75 in five southern Wyoming ranches. Although herd sizes varied seasonally and yearly, about 6,000 ewes and their lambs were monitored each year during spring lambing and the summer and winter grazing seasons. Most of the sheep were tended by herders. Lamb loss was greater than ewe, and spring losses were always greater than summer and winter losses combined. Of 4,440 dead sheep examined, predators killed 1,030 or 23%. Although predation was the largest single cause of death for lambs (24%), weather-related losses such as deaths from exposure, starvation, accidents or disease, if combined, would probably have been higher. Disease killed the most ewes (26%), with predation the second most important cause of death (18%). Of the deaths from predation, coyotes caused 77%, black bears 11%, and golden eagles 9%. During the 3 years, known predator kills were 0.2% of the ewes each year and 1.5%, 2.1%, and 3.2%, respectively, of the lambs from the study herds. There were 1,235 ewes and lambs missing, mostly after the summer season, mainly due to miscounting and loose management from one ranch.