Animals in urban areas that experience frequent exposure to humans often behave differently than those in less urban areas, such as exhibiting less vigilance or anti‐predator behavior. These behavioral shifts may be an adaptive response to urbanization, but it may be costly if animals in urban areas also exhibit reduced anti‐predator behavior in the presence of natural predators. In trials with only a human observer as the stimulus, urban squirrels exhibited reduced vigilance and anti‐predator behavior compared to those in less urban areas. Next, we exposed squirrels in multiple urban and less urban sites to acoustic playbacks of a control stimulus (non‐predatory bird calls), a natural predator (hawk), and dogs and recorded their vigilance and three different anti‐predator behaviors when a human approached them while either broadcasting one of these three playbacks or no playbacks at all. Squirrels at urban sites also did not differ in their behavioral responses to the playbacks from possible predators (hawks or dogs) when they were compared to those at less urban sites exposed to these playbacks. Urban squirrels also exhibited increased vigilance and anti‐predator behavior when exposed to a human paired with hawk playbacks compared to the control playbacks. Together, our results indicate that urban squirrels did perceive and assess risk to the natural predator appropriately despite exhibiting increased tolerance to humans. These results provide little support for the hypothesis that increased tolerance to humans causes animals to lose their fear of natural predators.

Animals in urban areas that experience frequent exposure to humans often behave differently than those in less urban areas, such as less vigilance or anti-predator behavior. These behavioral shifts may be an adaptive response to urbanization and caused by habituation to humans. A possible negative consequence is cross-habituation to natural predators where urban animals exhibit reduced anti-predator behavior in the presence of humans but also to their natural predators. We tested the hypothesis that habituation to humans in urban populations of fox squirrels (Sciurus niger) causes cross-habituation to stimuli from two possible predators (hawks and domestic dogs). We exposed squirrels in multiple urban and less urban sites to acoustic playbacks of a control stimulus (non-predatory bird calls), a natural predator (hawk), and dogs and recorded their vigilance and three different anti-predator behaviors when a human approached them while either broadcasting one of these three playbacks or no playbacks at all. In trials with no playbacks, urban squirrels exhibited reduced vigilance and anti-predator behavior compared to those in less urban areas but there was little evidence that urbanization altered the correlations among the different behaviors we quantified. Urban squirrels exhibited increased vigilance and anti-predator behavior when exposed to a human paired with hawk playbacks compared to the control playbacks. This indicates that urban squirrels did perceive and assess risk to the natural predator appropriately despite exhibiting habituation to humans. There is currently little evidence that habituation to humans causes animals to lose their fear of natural predators.