Eat or Be Eaten: Implications of potential exploitative competition between wolves and humans across predator- savvy and -naive deer populations

Abstract

Predator recolonization often evokes innate as well as learnt anti-predatory responses in prey. To test white-tailed deer risk allocation amidst an expanding wolf population in Michigan, we used a paired experimental approach to investigate deer behavior in areas with and without wolves. We treated sites with wolf urine, a novel scent (lemon juice), and a control (distilled water), and used remote cameras to observe deer vigilance, diel activity, and abundance before and after treatment. We also examined the effect of vegetation cover/predator ambush potential on deer vigilance. For most deer-response metrics, wolf urine had no effect irrespective of actual wolf presence or absence. However, we observed a difference in the overall diel pattern of deer in areas with wolf presence versus without. Further, we detected significant shifts in diel activity in both areas pre- and post-treatment. While such shifts were not consistent, we could detect a reduction in crepuscular deer activity in areas where deer coexist with wolves. While deer vigilance was typically unaffected by treatments, habitat cover was found to be pivotal. We observed a significant positive effect of vegetation cover on deer vigilance at sites where wolves were present. These results likely indicate that predator cues affect deer vigilance more acutely in denser habitats, which presumably facilitate higher predator success. We did not observe a similar response in the predator-naive deer population. In areas where human and non-human predators hunt the same prey, predator presence may thus negatively impact human hunting success through exploitative competition by making deer more vigilant. However, hunters may avoid such competition by choosing hunting/bait sites located in open areas. Our results on fundamental predation ecology have strong applied implications for fostering human-predator coexistence.