Wolf functional response and regulation of moose in the Yukon

We studied kill rates by wolves (Canis lupus) on a rapidly growing moose po pulation in the east-central Yukon. We added these data to the cumulative f unctional response curve obtained in other North American wolf studies. Our kill rates are higher than those predicted at low moose densities. The kil l rate increases rapidly, reaching 2.4 moose per wolf per 100 days at 0.26 moose/km(2) and remains constant at this level. No data are available below 0.2 moose/km(2) to indicate the shape of the ascending curve. Based on moo se distribution and the low prey-switching ability of wolves, we suggest th at the functional response curve is of type II. Our wolf predation rate mod el predicts that moose are held to a low density equilibrium between 0.07 a nd 0.12/km(2), slightly below densities observed in interior Alaska and the Yukon.