Ecology of fear alters behavior of grizzly bears exposed to bear-viewing ecotourism

Humans are perceived as predators by many species and may generate landscapes of fear, influencing spatiotemporal activity of wildlife. Additionally, wildlife might seek out human activity when faced with predation risks (human shield hypothesis). We used the anthropause, a decrease in human activity resulting from the COVID-19 pandemic, to test ecology of fear and human shield hypotheses and quantify the effects of bear-viewing ecotourism on grizzly bear (Ursus arctos) activity. We deployed camera traps in the Khutze watershed in Kitasoo Xai'xais Territory in the absence of humans in 2020 and with experimental treatments of variable human activity when ecotourism resumed in 2021. Daily bear detection rates decreased with more people present and increased with days since people were present. Human activity was also associated with more bear detections at forested sheltered sites and less at exposed sites, likely due to the influence of habitat on bear perception of safety. The number of people negatively influenced adult male detection rates, but we found no influence on female with young detections, providing no evidence that females responded behaviorally to a human shield effect from reduced male activity. We also observed apparent trade-offs of risk avoidance and foraging. When salmon levels were moderate to high, detected bears were more likely to be females with young than adult males on days with more people present. Should managers want to minimize human impacts on bear activity and maintain baseline age-sex class composition at ecotourism sites, multiday closures and daily occupancy limits may be effective. More broadly, this work revealed that antipredator responses can vary with intensity of risk cues, habitat structure, and forage trade-offs and manifest as altered age-sex class composition of individuals using human-influenced areas, highlighting that wildlife avoid people across multiple spatiotemporal scales.

Spatial prey availability and pulsed reproductive tactics: Encounter risk in a canid-ungulate system

Predation risk is a function of spatiotemporal overlap between predator and prey, as well as behavioural responses during encounters. Dynamic factors (e.g. group size, prey availability and animal movement or state) affect risk, but rarely are integrated in risk assessments. Our work targets a system where predation risk is fundamentally linked to temporal patterns in prey abundance and behaviour. For neonatal ungulate prey, risk is defined within a short temporal window during which the pulse in parturition, increasing movement capacity with age and antipredation tactics have the potential to mediate risk. In our coyote-mule deer (Canis latrans-Odocoileus hemionus) system, leveraging GPS data collected from both predator and prey, we tested expectations of shared enemy and reproductive risk hypotheses. We asked two questions regarding risk: (A) How does primary and alternative prey habitat, predator and prey activity, and reproductive tactics (e.g. birth synchrony and maternal defence) influence the vulnerability of a neonate encountering a predator? (B) How do the same factors affect behaviour by predators relative to the time before and after an encounter? Despite increased selection for mule deer and intensified search behaviour by coyotes during the peak in mule deer parturition, mule deer were afforded protection from predation via predator swamping, experiencing reduced per-capita encounter risk when most neonates were born. Mule deer occupying rabbit habitat (Sylvilagus spp.; coyote's primary prey) experienced the greatest risk of encounter but the availability of rabbit habitat did not affect predator behaviour during encounters. Encounter risk increased in areas with greater availability of mule deer habitat: coyotes shifted their behaviour relative to deer habitat, and the pulse in mule deer parturition and movement of neonatal deer during encounters elicited increased speed and tortuosity by coyotes. In addition to the spatial distribution of prey, temporal patterns in prey availability and animal behavioural state were fundamental in defining risk. Our work reveals the nuanced consequences of pulsed availability on predation risk for alternative prey, whereby responses by predators to sudden resource availability, the lasting effects of diversionary prey and inherent antipredation tactics ultimately dictate risk.