Mammals forage under different constraints that affect foraging efficiency. These constraints range from direct predatory cues (e.g. urine) to indirect cues that influence predation risk such as cover or ambient moonlight. The fear of predation via direct predatory cues is an important constraint and may have a strong behavioral effect on mammals. We measured how foraging behavior of Woodland Deer Mice (Peromyscus maniculatus gracilis) changed on different substrate types (indirect cues) in the presence or absence of predator scents (direct cues). To test these effects, we captured wild mice and tested their responses in experimental laboratory trials. The treatments used in trials consisted of an indirect cue, substrate (wet or dry paper leaves), and a direct olfactory cue (mink urine or water). Mice responding to predation cues are expected to forage more often on wet leaves (a quiet substrate) in the absence of predator scent.
Results/Conclusions
We found that P. maniculatus foraged more often on the dry-leaf substrate with water as a control predator scent (F[1,24] = 7.56, P = 0.011), counter to our hypothesis. In addition, we discovered that P. maniculatus on average handle seeds longer in the presence of mink urine (F[1,24] = 6.24, P = 0.019). P. maniculatus incurred a time-cost for being vigilant and subsequently spent more time handling seeds when mink urine was present. These results suggest that olfactory cues do affect P. maniculatus foraging behavior and may be more influential than substrate type, contrary to recent findings on the interaction of indirect and direct cues. These findings are important for understanding how rodents balance their energy budgets with perceived predation risk and are consistent with optimal foraging theory.