Proceedings of the Vertebrate Pest Conference

Mortality of sheep and lambs from all causes and from predator losses from 1940 through 1985 for the United States is presented including economic aspects. Lamb losses from all causes were 9% of the lamb crop in 1940 and were generally higher thereafter and reached a peak in 1978 of 14%. Losses of sheep 1 year old and older from all causes were 7.5% in 1940, remained somewhat higher through the '60s, and then declined to a low of 5.2% in 1985. Calculation of predator losses were based on an upward trend of lamb losses relative to sheep losses with increasing losses to predators. Estimates of predator losses were conservative and probably were underestimated. Predator losses were lowest in 1940 at 2.85%, increased during World War II, remained moderately high through the '50s, and then increased to a peak of 6.07% of all sheep and lambs in 1977. Losses declined following the advent of the parvovirus in 1978 to a low of 5.24% in 1981 and then increased to 5.69% in 1985. Monetary losses from predators showed a steady increase from $13 million in 1940, to almost $90 million in 1979, and almost $69 million in 1985. Total losses from 1960 through 1985 were $1.2 billion. Predator losses as a percent of net income increased from 23% in 1940 to 26% in 1960, and to 78% in 1979. After reduction in predator losses due to the parvovirus they were still 60% of net income in 1985. Obviously, predator losses have been a dominant factor in the decline of the sheep industry.