Hunter or hunted? Perceptions of risk and reward in a small mesopredator

Apex predators directly and indirectly influence prey and predators at lower trophic positions (mesopredators). The lethal effect of apex predators on mesopredators is well documented, but they also could affect mesopredators in non-lethal ways. We investigated foraging decisions and perceived risk in the bat-eared fox (Otocyon megalotis), a small canid that is often killed by larger terrestrial carnivores and birds of prey. We used giving-up-density (GUD) experiments and observations of vigilance behavior to assess the influence of temporal, spatial, and anthropogenic factors on perceived risk in a population of bat-eared foxes at the Kuruman River Reserve, Northern Cape, South Africa. GUDs were higher during periods around the new moon and lower in the presence of researchers, suggesting that foxes are warier in darker conditions, but perceive an increase in relative safety in the presence of humans. Vigilance, however, did not vary with these same factors. Observational data revealed foraging success outside the experimental context did not differ with lunar period, implying that higher GUDs associated with new moons were not due to higher missed opportunity costs associated with foraging at patches. These results suggest that GUDs may be capable of detecting more subtle differences in perceived risk when compared to vigilance rates. We highlight the important considerations of using GUDs to examine perceived risk for a predatory species and emphasize that future studies using GUDs should quantify predators’ risk-related decisions by documenting missed opportunity costs to determine the implications behind patch-use behavior.