Wolf Research

Developing a Method to Determine Seasonal Shifts in the Diets of Wild Gray Wolves (Canis Lupus)

The Environment and Natural Resources Institute, University of Alaska, Anchorage, Anchorage, AK, USA http://www.uaa.alaska.edu/enri/

The Alaska Zoo, Anchorage, AK, USA

Determining seasonal shifts in the dietary ecology of gray wolf (Canis lupus) populations in North America is of great interest to researchers and managers, and is the focus of multiple recent studies in Alaska. This interest stems from the iconic nature and potential ecological importance of wolves, as well as the historic relationship between wolves and humans.

Carbon (13C) and nitrogen (15N) stable isotope analysis is a tool to study gray wolf dietary ecology. This technique makes use of the predictable fashion in which the isotope values of foods are incorporated into consumer tissues. However, despite its predictability, the affiliation between the isotopic values of foods and consumer tissues is rarely perfect. Instead, we see a slight disconnect (off set) between the isotopic values of resources and animal tissues. This disjunction, termed diet to tissue discrimination (δ13C tissue - δ13Cdiet or δ15Ntissue - δ15Ndiet, where δ is a standardized method of expressing isotope abundance) can vary in magnitude between species, tissues, and diets. Given this variation, a reliable understanding of the diet to tissue discrimination value for a particular consumer/resource combination is essential to drawing accurate conclusions on the types and quantities of resources consumed by animals in the wild.

With the help of the Alaska Zoo wolf pack, we are conducting an experiment designed to measure tissue-diet differences for 13C and 15N in gray wolf hair, blood, and vibrissae (whiskers). These tissues are popular for use in isotope – based dietary studies of large mammals. During the summer and fall of 2012, the wolves received an isotopically - consistent diet. We can measure diet to tissue discrimination in hair, blood, and vibrissae by comparing the δ13C and δ15N values of dietary resources to the δ13C and δ15N values of hair and vibrissae grown using these resources. With the help of the Alaska Zoo wolf pack, we will produce the necessary parameters to interpret stable isotope data from wild – caught wolves. Thus, allowing for a better understanding of wolf ecology and wolf management.

Resources:

Martinez del Rio, C., Wolf, N., Carleton, S. and Gannes, L. (2009). Isotopic ecology ten years after a call for more experiments. Biological Reviews. 84, 91-111.

Adams, L. G., S. D. Farley, C. A. Stricker, D. J. Demma, G. H. Roffler, D. C. Miler, and R. O. Rye. (2010). Are inland wolf-ungulate systems influenced by marine subsidies of Pacific salmon? Ecological Applications. 20, 251–262.

Darimont, C. T., and T. E. Reimchen. (2002). Intra-hair stable isotope analysis implies seasonal shift to salmon in gray wolf diet. Canadian Journal of Zoology. 80:1638–1642.