Mountain Lion Predation on Endangered Woodland Caribou, Mule Deer, and White-tailed Deer

Cougar (Puma concolor) predation on endangered woodland caribou (Rangifer tarandus caribou) may be accelerating their decline. Recent changes in forestry practices from large to smaller, more numerous harvest units has increased forest fragmentation and edge, which favors white-tailed deer (Odocoileus virginianus). High deer populations may support more cougars, indirectly resulting in more caribou mortalities from cougar predation. Forest fragmentation also may increase cougar predation of caribou if cougars concentrate on forest edges while hunting and attack caribou more successfully in small versus large forest patches. We are investigating the effects of forest patterns on where caribou mortalities from cougar predation occur. Although habitat management may ultimately be needed to recover caribou, immediate action to prevent extirpation of caribou herds through predator control may be needed also. However, managers first must know whether all cougars kill caribou, necessitating large-scale reduction in cougar numbers, or whether only specific cougars kill caribou, requiring removal of only specific cougars. We are using radio telemetry to document 1) spatial and habitat relationships among cougars, caribou, and deer; 2) sites where cougars kill ungulates; 3) which cougars kill caribou; and 4) how removing caribou-killing cougars affects caribou survival. Since 1999, we have radio-collared 22 cougars, 23 caribou, 43 mule deer (O. hemionus), and 30 white-tailed deer. Despite close proximity of all cougars to caribou habitat, only two cougars spent significant time within occupied caribou range. One male cougar killed at least two caribou and he was removed. Our preliminary results suggest that large-scale reduction in cougar numbers to reduce caribou mortalities may be unjustified.