Prugh, L.R., Arthus, S.M. & Ritland, C.E. 2008: Use of faecal genotyping to determine individual diet. - Wildl. Biol. 14: 318-330.
Faecal genotyping has been proposed as a method to examine the diets of individuals, but this application has been virtually unexplored by wildlife biologists. We used faecal genotyping and conventional scat analysis to determine the diets of 42 coyotes Canis latrans belonging to nine social groups in Alaska. We use rarefaction to examine the effect of scat sample size on the accuracy and precision of individual diets, and we simulate diets from scats to determine how diet richness and evenness affect sample size requirements. We then demonstrate the utility of this technique by examining variation in diet among individual coyotes and social groups in relation to prey availability. Estimates of diet diversity and composition were highly variable when < 10 scats were used to construct the diet. Diets simulated with a uniform (i.e. even) distribution of prey items required generally smaller sample sizes to estimate diet diversity and richness than diets with exponentially distributed items; however, items in actual scats were exponentially distributed. We found moderate dietary variability among individuals in our study area, and diet overlap was higher among coyotes within social groups than between groups. As predicted by optimal foraging theory, the niche widths of all coyote groups expanded as their primary prey (the snowshoe hare Lepus americanus) became scarce during our three-year study. Despite increased niche width, diet overlap among groups remained constant, suggesting that coyotes selected differing alternative prey. Spatiotemporal variation in snowshoe hare availability explained 70% of the variation in hare consumption among groups, indicating that variation in local
prey availability may be the primary cause of diet variation among coyotes. Although faecal genotyping can be used to address ecological questions at the individual level, studies should be designed specifically for this purpose so that sufficient numbers of faeces can be obtained.
Key words: Alaska, canid, faecal genotyping, individual specialization, noninvasive genetics, rarefaction, resource use
Laura R. Prugh*, Zoology Department, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada - e-mail: prugh@nature.berkeley.edu Carol E. Ritland, Genetics Data Centre, UBC Department of Forest Sciences, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada - e-mail: critland@interchange.ubc.ca
*Present address: UC Berkeley, Environmental Science, Policy, and Management, 137 Mulford Hall, Berkeley, CA 94720, USA
Corresponding author: Laura R. Prugh
Received 28 June 2007, accepted 17 September 2007
Associate Editor: Lisette Waits