White-tailed deer (Odocoileus virginianus) in the midwestern and eastern United States typically persist at very high population densities. One cause contributing to high deer densities is minimal adult mortality due to natural predation. Coyotes (Canis latrans) overlap with much of the range of white-tailed deer. However, whether coyotes regularly consume adult deer or strictly fawns is a topic of debate. If coyotes do not prey upon adult deer though, it is still expected that deer will make fine-scale movements to avoid exposure to a potential threat.
We conducted a giving-up density (GUD) experiment that examined whether white-tailed deer avoided foraging in areas when indirect evidence (urine) of coyotes was present. The GUD indicates the amount of food that an animal is prepared to consume at a given location before it forages elsewhere. At three sites in northeast Ohio, we examined GUDs on transects that had feeders located at the forest-grassland ecotone and then 20 m and 60 m from the ecotone in both the forest and grassland. We collected baseline data six days prior to urine treatment. After the baseline, every feeder on a single transect at each of our sites received 10 ml coyote urine for six additional days.
Results/Conclusions
We found that the GUDs of white-tailed deer were influenced by the presence of coyote urine. Feeders located on the transects that received urine treatment had higher GUDs (high GUDs indicate reduced preference) than they did in the six days prior to receiving treatment. Feeders that received urine treatments also were found to have higher GUDs than other feeders at the same habitat and distance locations (e.g. woods at 20 m) that did not receive the urine treatment. However, increased GUDs associated with coyote-urine treatments only persisted for the first three days of the six day treatment. This short-term effect indicates that white-tailed deer only feared indirect cues for a short period without a direct threat being present. Future research examining the effects of indirect predatory cues should be done at a larger spatial scale, and in multi-predator systems. This will enable even further understanding of the foraging preferences and habitat use of white-tailed deer.