Seasonal patterns in foraging and predation of gray wolves in Yellowstone National Park

Metz, Matthew; Vucetich, Douglas; Stahler, Daniel; Peterson, Rolf

Understanding predation among vertebrate species living in temperature climates requires understanding how kill rate varies among seasons of the year. Unfortunately, summer kill rates are difficult to measure and are rarely available, even for well-studies species like wolves (Canis lupus). Monitoring GPS-collared predators represents a method that might overcome these difficulties. Here, we used GPS collars to estimate summer kill rates for several wolf packs between 2004 and 2009 in Yellowstone National Park, North America. This represents the second use of GPS collars to estimate summer kill rates for wolves and the first use in a population where estimation was complicated by wolves tendency to feed only from a portion of the kills made by a pack. To account for this behavior, we used the principles of the double-count method,which was designed to estimate abundances when the probability of detecting an individual is less than one. This application of the double-count method relies on estimating the probability that an individual wolf would be detected at the carcass of a prey. The probability of detection was 0.72 (+ or - 0.05 SE) for large ungulate carcasses and 0.46 (+ or - 0.04 SE) for small ungulate carcasses. If we had accepted the default presumption that each wolf in a pack feeds from each carcass, then our estimate of summer kill rate would have been only 67% of what we actually estimated them to be. WWe also used GPS collars (deployed during summer) and VHF collars (deployed during winter) to examine how the probability of detection varies among seasons and among different kinds of wolves. We discuss these results in the context of better understanding wolf social behavior. Finally, estimating summer kill rates for wolves is further complicated by the need to account for differences in metabolic rate between pups and adults. In this paper, we show how estimates of kill rate are affected by different methods of accounting for the lower metabolic rates of pups.

Seasonal patterns in foraging and predation of gray wolves in Yellowstone National Park

Series

Collections