Date of this Version
Aerial hunting is commonly used by agriculture agencies in the Intermountain West to reduce coyote (Canis latrans) predation on domestic sheep. We assessed the effect of aerial hunting of coyotes on sheep losses to coyotes, and the need for corrective predation management (hours of work, device nights) on the same pastures when sheep arrived for the subsequent summer grazing season (3-6 months after aerial hunting). Comparisons were made between paired pastures with (treated) and without (untreated) winter aerial hunting from helicopters. Average (x ± SE) pasture size was 45.2 ± 14.1 km2 (n = 21) for treated pastures and 30.9 ± 4.6 km2 (n = 21) for untreated pastures. There was an average of 1,098 ± 88 ewes and 1,226 ± 149 lambs in treated pastures, and 1,002 ± 149 ewes and 1,236 ± 79 lambs in untreated pastures. The number of dead lambs located and confirmed killed by coyotes (confirmed kills) was less in treated pastures (2.7 ± 0.6) than in untreated pastures (7.3 ± 1.6; P = 0.01). To estimate total lamb losses to coyotes, we multiplied the proportion of known lamb deaths that were confirmed coyote kills by the number of missing lambs and added the resulting figure to the number of confirmed kills. These estimates of lamb loss to coyotes were also lower in treated (11.8 ± 6.2) than untreated pastures (35.2 ± 8.1; P = 0.02). Hours required for summer coyote control also were less (P = 0.01) in treated pastures (37.3 ± 8.5) than in untreated pastures (57.2 ± 11.3). Winter aerial hunting increased the mean number of coyotes killed annually per pasture from 2.0 ± 1.0 to 5.7 ± 1.1 (P = 0.04), but it did not affect the number of coyotes removed during summer coyote control (P = 0.52). Based on 1995 values for Utah lambs and labor, winter aerial hunting of coyotes had a benefit:cost ratio of 2:1:l.