Effects of Wolf Removal on Livestock Depredation Recurrence and Wolf Recovery in Montana, Idaho and Wyoming

Abstract

Wolf predation on livestock and management methods used to mitigate conflicts are highly controversial and scrutinized especially where wolf populations are recovering.  Wolves are commonly removed from a local area in attempts to reduce further depredations, but the effectiveness of such management actions is poorly understood.  We compared the effects of 3 management responses to livestock depredation by wolf packs in Montana, Idaho, and Wyoming:  no removal, partial pack removal, and full pack removal.  From 1989 to 2008, we documented 967 depredations by 156 packs: 228 on sheep and 739 on cattle and other stock.  Median time between recurrent depredations was 19 days following no removal (n = 593), 64 days following partial pack removal (n = 326), and 730 days following full pack removal (n = 48).  Partial pack removal was most effective if conducted within the first 7 days following depredation, after which there was only a marginally significant difference between partial pack removal and no action (HR = 0.86, P = 0.07), and no difference after 14 days (HR = 0.99, P = 0.93).   Ultimately, pack size was the best predictor of a recurrent depredation event; the probability of a depredation event recurring within 5 years increased by 7% for each animal left in the pack after the management response.  However, the greater the number of wolves left in a pack, the higher the likelihood the pack met federal criteria to count as a breeding pair the following year toward population recovery goals.