B&C Fellow - Jonathan Derbridge

University of Montana - Masters - 2010
Summer diet of wolves in Northwestern Montana

After a life outside wildlife in the UK, I moved to California to start a belated college career at a community college in the Bay Area. I developed an interest in natural history and a taste for field work during a series of summer technician jobs on the wolf projects in Minnesota and Idaho. After transferring to the Conservation and Resource Studies B.S. program at UC Berkeley I continued to expand my wildlife academic and field experience through classes at Berkeley and technician positions in Montana working for the newly state-run wolf program. After graduating with highest honors from the University and the College of Natural Resources in 2006, I took a position as a technician with the Montana Fish, Wildlife & Parks wolf program that lasted until the end of the year. During 2007, I worked as an environmental educator for the YMCA in a coastal California National Park, teaching students from K-12. Paul Krausman accepted me as one of his first 2 Boone and Crockett Wildlife Conservation Program students in Fall 2007, and I started classes in the Wildlife Biology program, and project preparation in January 2008.

ANALYSIS OF GRAY WOLF DIETS IN NORTHWESTERN MONTANA

Our research will characterize the diets of gray wolves in northwestern Montana through the use of traditional scat analysis methods and the more recently developed technique of stable isotope analysis. We will use these methods to analyze scats and hair to determine diets, and summarize the relative merits of each method. Our results will comprise the first step in understanding the ecosystem effects of a recently reestablished top predator, and provide insights to how future diet analysis should be conducted.

Since the reintroduction of wolves to Yellowstone National Park, and central Idaho in 1995 and 1996, the species' recovery has been steady and successful. Wolves have been breeding in northwestern Montana's multi-prey ecosystem since the early 1980s, but only since 2005 has the population in that part of the state grown substantially. As the wolf population grows, there is an interesting opportunity to monitor this top predator's diet. No accurate data on what wolves in northwestern Montana eat are currently available, but a variety of methods for providing this information can be used. 

Traditionally, carnivore diets have been described through fecal analysis. This involves the collection of scats from the field and an examination of their contents. There are, however, some key problems with the accuracy of this method, such as the difficulty of collecting a sample that adequately represents a pack's diet over a period of time, and the over-representation of small prey in scat contents due to unequal digestibility of different-sized prey. Stable isotope analysis uses the guard hairs of wolves to ascertain a full record of diet over the period of growth and, thus, is free of such problems. This technique may represent the future of diet analysis, and by conducting both diet analysis methods on the same wolf populations over the same time period we will be able to compare methods.

In order to determine the feasibility of collecting the necessary data, preliminary field work began earlier this year. Between May and October, 2008 we collected scats from 3 wolf packs in northwestern Montana. These scats will provide a record of each pack's diet, and will be analyzed using well tested methods. Guard hairs of gray wolves grow from May to October, and as a result of metabolic processes those hairs also contain a record of an animal's diet. Hairs will be collected from wolves between November 2008 (once they are fully grown) and July 2009 (during the annual molt). As the collection and analysis of hairs is far less time-consuming, we will collect hairs for SIA from 10 northwestern Montana packs. Thus, samples we collect will provide data with which to compare analysis methods, and thoroughly describe the diets of wolves between May and October.