The influence of environmental and social factors on high- and low-cost vigilance in bat-eared foxes

Abstract

Vigilance is commonly used to assess anti-predator behavior; however, the majority of studies assess only high-cost vigilance, which interrupts any other activities. Low-cost vigilance, by comparison, allows animals to be vigilant while engaged in other activities, thereby reducing the cost of vigilance. Here, we investigate the use of high- and low-cost vigilance in relation to environmental and temporal factors in a wild population of the bat-eared fox (Otocyon megalotis), a small mesopredator, using behavioral observations of eight habituated animals. We hypothesized that vigilance would increase with tall, dense vegetation, high wind speeds, and low ambient light, and that vigilance would decrease in the presence of conspecifics and over the period of a single observation session. Overall, bat-eared foxes spent significantly more time engaged in low-cost vigilance than in high-cost vigilance. High-cost vigilance increased with vegetation height, in the presence of adult conspecifics and in winter. We suggest these effects are due to impeded lines of sight with increases in vegetation height, increased competition in the presence of conspecifics, and increased social interactions in winter. Low-cost vigilance was highest at the start of observational sessions, and we suggest that this is due to observer effects, as foxes demonstrated increases in both high- and low-cost vigilance specifically towards observers during this time. This study demonstrates that foxes are highly dynamic in their vigilance behavior. Due to the low predation pressure in the study area, the use of mostly low-cost vigilance may be sufficient in this environment, and thus foxes can allocate more time to other activities. Our results indicate that, in this environment, vigilance is most likely driven by factors other than predation risk, but that foxes may still respond to certain cues of predation risk. Ultimately, in areas of low predation risk, species susceptible to predation may retain responses to cues of risk, but adapt behaviors to reduce the associated costs. While studies examining perceived risk in herbivores frequently assess vigilance, the examination of vigilance is largely under-investigated in mesopredators. Here, we present findings from one of the first studies to examine high- and low-cost vigilance in a small mesopredator. We demonstrate that in an area with minimal predation pressure low-cost vigilance is more intensively used and that despite the absence of predator sightings, ambush predators may still pose a perceived threat to foxes. Ultimately, when predation pressure is low, social interactions and competition may be some of the costliest activities. Results further indicate that while this small canid habituates quickly to observer presence, the initial presence of observers cannot be considered truly neutral.