The gray wolf-scavenger complex in Yellowstone National Park

The reintroduction of gray wolves (Canis lupus) to Yellowstone National Park in 1995 provides a natural experiment in which to study the effects of a keystone predator on ecosystem function. Gray wolves often provision scavengers with carrion by partially consuming their prey. In this dissertation, I seek to understand the causes of partial carcass consumption by wolves and quantify the impact of this predator mediated food supply on sympatric meat eating species. In addition, I compare scavenging at human hunter killed-elk (Cervus elaphus) to wolf-killed elk, and predict how a changing climate will affect the scavenger complex.; I found that the percent of an elk carcass consumed by wolves increases as snow depth decreases and the ratio of wolf pack size to prey size and distance to the road increases. In addition, wolf packs of intermediate size provide the most carrion to scavengers. My results also demonstrate that wolves increase the time period over which carrion is available from pre-wolf conditions, and change the variability in scavenge from a late winter pulse dependent primarily on abiotic environmental conditions to one that is relatively constant across the winter and primarily dependent on wolf demographics. Wolves also decrease the year-to-year and month-to-month variation in carrion availability. By transferring the availability of carrion from the highly productive late winter, to the less productive early winter and from highly productive years to less productive ones, wolves provide a temporal subsidy to scavengers.; Understanding the mechanisms by which climate and top predators interact to affect community structure accrues added importance as humans exert growing influence over both climate and regional predator assemblages. In Yellowstone, winter severity and reintroduced gray wolves together determine the availability of winter carrion on which numerous scavenger species depend for survival and reproduction. I analyzed 55 years of weather data from Yellowstone and found that winters are getting shorter, as measured by the number of days with snow on the ground, because of decreased snowfall and an increase in the number of days where the temperature exceeds freezing. I demonstrate that in the absence of wolves, early snow thaw implies that late-winter carrion will be substantially reduced, potentially causing food bottlenecks to develop for scavengers. (Abstract shortened by UMI.)...