Relative vulnerability of coyotes to removal methods on a northern California ranch

Evidence suggests that predation on domestic sheep by coyotes (Canis latran s) is caused primarily by breeding pairs with territories overlapping sheep . Accordingly we investigated vulnerability of coyotes to removal methods r elative to factors associated with reproduction and territoriality. We coll ected live and lethal coyote capture data during April 1993-February 1998 o n a north-coastal California sheep ranch. Routine coyote removal was conduc ted in response to sheep depredation before and during (part on the study. Younger (nonbreeding) coyotes generally were more vulnerable to capture tha n older (potentially breeding) individuals, although age bias varied among removal methods. Recaptures of radiocollared coyotes in foothold traps and snares indicated a bias toward progressively younger individuals (juv > yea rling > ad; P = 0.002). Proportionally more juvenile and yearling coyotes w ere removed by M-44s (sodium cyanide ejectors) than by traps and snares (P = 0.016). We found no difference between traps and snares in the ages of co yotes taken (P = 0.50). Vulnerability of younger coyotes was likely elevate d by lack of experience and more time spent in unfamiliar areas where they were least able to avoid capture devices. Coyotes were caught more often th an expected outside of core areas of their territories with both traps (P = 0.001) and snares (P = 0.02). Older coyotes were most vulnerable in spring and summer when rearing pups, after most depredation occurred. Radiocollar ed breeders (P = 0.012) and uncollared coyotes of breeding age (P = 0.052) were captured less often during the non-pup-rearing period than the pup-rea ring period. These results suggest conventional control in northern Califor nia is poorly suited to the segment of the coyote population killing the mo st sheep, particularly during the time of year when most sheep depredation occurs. Efficacy of control methods might be improved by conservative use o f conventional devices to minimize learned avoidance by coyotes, and by gre ater reliance on methods such as livestock protection collars that are spec ific to depredating individuals throughout the year.