Effects of levels of human exposure on flight initiation distance and distance to refuge in foraging eastern gray squirrels (Sciurus carolinensis)

Abstract

Flight initiation distance (FID), the distance at which an organism begins to flee from an approaching predator or threat, is associated to prey escape decision-making processes with benefit and cost trade-offs to remaining in a patch. Factors that may affect FID can be altered by human-stimulated predation risk, although the magnitude of response may depend on human exposure. We investigated how FID and distance to refuge of foraging eastern gray squirrels ( Sciurus carolinensis Gmelin, 1788), vary in seven sites corresponding to three levels of human exposure. We predicted that both FID and distance to refuge increase as exposure to human stimuli decreases; FID increases with the starting distance of the approaching human; and FID increases with distance to refuge. We found that FID increased with decreasing human exposure and that FID increased with increasing starting distance. We found no difference in distance to refuge between exposure levels. Our results suggest that risk posed to gray squirrels in areas frequently visited by humans is minimized or reduced, leading to differences in FID between exposure levels and may be attributed to habituation to increased nonlethal stimuli in the form of exposure to humans.