Predation dynamics of Mexican wolves in Arizona and New Mexico

The success of the Mexican wolf reintroduction project is based on whether captive reared animals can successfully prey on native livestock.  This is particularly important because almost all of the Mexican wolf recovery area has seasonal and year around grazing leases, and therefore livestock are available to wolves.  This is unlike the recovery areas in the Northern Rocky Mountains where there are large tracts of land without livestock (e.g., Yellowstone, Frank Church wilderness).  Historic reports of the diet of Mexican wolves, suggest that deer were their main food source.  But, these studies were conducted when the native Merriam’s elk were extirpated and Rocky mountain elk had not yet been translocated.

Therefore, as the reintroduction project moved forward, it was very necessary to develop a baseline for Mexican wolf diet.  The first diet study was based on years of opportunistic scat collection throughout the entire year.  Although this study was instrumental in developing a baseline knowledge of Mexican wolf diet, it did not comment much about pack-based variation, nor seasonal variation.  Furthermore, diets may change over time, and continued monitoring of Mexican wolf diet is necessary to understand predation and the success of the reintroduction.

My research was based on summer diet over 2 years.  We collected scats both opportunistically on roads and trails, and also at den sites.  We estimated pack-based diets, and overall diets of Mexican wolves.  Elk (Cervus elaphus) comprised 80.3% of diet of the Mexican gray wolf. Other prey included domestic cattle (16.8%), deer (Odocoileus spp.; 1%), squirrels (1%), other rodents (2%), and lagomorphs (1%).  Furthermore, in areas of year-around grazing, 21% more livestock were consumed, compared to areas grazed seasonally.  The implications of this research suggest that wolves can successfully capture and kill native livestock.  Furthermore, they do eat domestic livestock, but the amount of domestic livestock in the diet is pack-specific, and increases when wolves are exposed to year around grazing.  This means that some packs can live amongst cattle without preying on them, but in certain areas with consistent livestock presence, certain packs will always kill livestock (Merkle et al. 2009).

Collaborators: P. R. Krausman, School of Natural Resources at University of Arizona, U. S. Fish and Wildlife Service, Arizona Game and Fish Department, New Mexico Game and Fish