Date of Award:

1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Advisor/Chair:

John P. Workman

Abstract

To provide accurate data concerning sheep losses resulting from predation, a verification study of sheep predation was initiated in March 1972 in the Cedar City area of Utah. In cooperation with the Cedar City Wool Growers Association and Southern Utah State College Experimental Farm, ten sheep ranches were chosen as sample operations, forming the data base for the initial phase of the study (1972-1974).

Cooperating ranchers were asked to promptly report all sheep carcasses or injured sheep, so that an examination could immediately be made to ascertain the cause of death or injury. Daily horseback searches were also conducted on the spring and summer ranges. Every located sheep carcass was examined to determine cause of death. If a predator was responsible, the kill was photographed and location, date, species of predator and age class of carcass was recorded. Coyotes were the principal predator inflicting 89 to 100 percent of the kills. Lambs were the principal age class of predator kills.

The number of sheep carcasses found and verified as predator kills and natural losses was substantially less than the total number lost. Therefore, a proportion was used to estimate the total predation rate. The average predation rate was 5.9 percent expressed as a percent of lamb crop. In the final year of the study (1975) three herds were chosen and research efforts were intensified and the validity of the statistical inference was confirmed.

An estimated total predation loss of 3028 lambs was incurred by herds 1-10 in 1972 to 1974. In 1975, 158 lambs were destroyed by predators in herds 1, 3 and 5. These losses were valued at $89,347.

Assuming the sample predation rate is representative of predation losses throughout Utah, the state-wide lamb loss to predators was calculated to be 127,521 lambs, representing a direct income loss to the Utah sheep industry of $3,622,061. The indirect or multiplier losses represented an additional $10,072,911 loss to the state economy.

Two models were developed. The first, a cost model, illustrated the nature of the costs of coyote predation, their effects upon the rancher and several approaches to profit maximization with and without coyote predation. The second model approached predation economics from a biological standpoint to identify research needs for future inquiries into predation economics. The relationships between coyote population dynamics, coyote control and predatory sheep losses were discussed, leading to the formulation of an economic production function model. The model provides a conceptual framework to determine the effectiveness and optimum rate of predator control efforts.

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