Coyote foraging ecology and selection for white-tailed deer fawns

Background/Question/Methods In the past decade coyotes have increased their range and density in northeastern North America and have established themselves as the top predator in the region. The addition of this prolific predator holds unknown consequences for white-tailed deer. If coyotes select for fawns in greater proportion to their availability under high and low deer density, then predation may limit growth of the deer populations. We evaluated whether diet selection and foraging behavior (movement paths and resource selection) varied as a function of fawn availability in two study areas in rural New York State that varied in coyote:deer ratios. We identified prey remains in coyote scat (N = 65-101) and estimated per capita fawn consumption based on coyote energy requirements in early and late summer 2007-2008.  To track searching behavior, we collared 14 coyotes with GPS units that that had a 20 min-6 hr fix schedule. We expected coyotes to selectively use open areas where fawns were disproportionately killed.  Further, we expected that the percentage of June locations in open habitat would be positively correlated with path tortuosity (indicating intensive search). Results/Conclusions Fawns comprised 47-54% of the coyote diet in summer, unexpectedly being lower in areas of higher deer density.  After correcting for differences in coyote population structure, the average coyote consumed 2.1-2.5 fawns in early summer and 0.5-0.9 fawns in late summer (the low deer density site having lower values), indicating that consumption of fawns did not differ with varying predator or prey densities. Coyotes in the low deer density site avoided open habitat in June when fawn consumption was greatest but selected for open habitat in August.  In the high deer density site there was no selection by coyotes for open habitat. There was also no correlation between the time coyotes spent in open habitat and path tortuosity (R^2 = 0.02, p = 0.0001) indicating that search effort was fairly constant regardless of habitat structure. While coyotes did not consume fawns in proportion to their availability, they did not search specifically for fawns above other prey items in either site. High density coyote populations may consume a greater proportion of available fawns, but if coyotes are not selectively foraging for fawns we can not conclude that coyote predation would significantly limit population growth.