Domestic sheep ranchers generally perceive abundances of natural prey and coyotes (Canis latrans) as important factors affecting coyote predation rates on sheep. To determine the effect of a changing natural prey base on coyote predation rates, we estimated coyote density and predation rates on ewes and lambs during part of 1 cycle of black-tailed jackrabbit (Lepus californicus) abundance on a 2,300 km2 area of the Idaho National Engineering Laboratory in southcentral Idaho from 1979-1985. We used 100, 1.6-km scat collection lines and 80, 1.6-km flushing transects to assess coyote and jackrabbit densities, respectively. Ewe and lamb loss rates were determined from questionnaires sent to all 13 producers grazing sheep on the area. Spring coyote density varied from 0.10 to 1.39 coyotes km-2 in response to a systematic fluctuation in jackrabbit density from 0 to 243 jackrabbits km-2. Reported total loss rates of ewes and lambs varied from 2.2 to 42.1 ewes/10(5) ewe-days and 33.0 to 163 lambs/10(5) lamb-days and were linearly and directly related to coyote density (P < 0.005). Ewe and lamb loss rates were independent of jackrabbit density (P > 0.18) except for 1 year when jackrabbits were virtually absent from the study area and the loss of lambs escalated dramatically. Our data suggest the increased losses of lambs resulted from reduced buffering by natural prey. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020
Scholarly peer-reviewed articles published by the Society for Range Management. Access articles on a rolling-window basis from vol. 1, 1948 up to 5 years from the current year. Formerly Journal of Range Management (JRM). More recent content is available by subscription from SRM.