Risky behavior and its effect on survival: snowshoe hare behavior under varying moonlight conditions

Abstract

Predation and predation risk can exert strong influences on the behavior of prey species. However, risk avoidance behaviors may vary among populations of the same species. We studied a population of snowshoe hares (Lepus americanus) near the southern edge of their range, in Pennsylvania. This population occupies different habitat types, experiences different environmental conditions, and are exposed to different predator species and densities than northern hare populations; therefore, they might exhibit differences in risk avoidance behaviors. We analyzed hare survival, movement rates, and habitat use under different levels of predation risk, as indexed by moonlight. Similar to previous work, we found snowshoe hare survival decreased with increased moon illumination during the winter, but we found differences in behavioral responses to increased predation risk. We found that snowshoe hares did not reduce movement rates during high‐risk nights, but instead found that hares selected areas with denser canopy cover, compared to low‐risk nights. We suggest that behavioral plasticity in response to predation risk allows populations of the same species to respond to localized conditions.

Use of Acceleration and Acoustics to Classify Behavior, Generate Time Budgets, and Evaluate Responses to Moonlight in Free-Ranging Snowshoe Hares

“…We removed all nights preceding a snowfall measurement >0, and all times when the relative humidity was >85%, since cloud cover is highly correlated with relative humidity (Sandor et al, 2000). Although we did not measure moonlight illumination levels ourselves and do not know the exact values that occurred, moon phase and lunar position are commonly used in studies of the effects of moonlight on wildlife (e.g., Johnson and De León, 2015;Gigliotti and Diefenbach, 2018).…”

Contingent strategies of risk management by snowshoe hares

“…It thus appears that hares tune their foraging to match the effectiveness of vigilance at reducing risk in different contexts and conditions. Gigliotti and Diefenbach (2018) reached a similar conclusion: flexible behaviour allows hares to match risk avoidance with local conditions. Vigilance alone cannot ameliorate risk that effects changes in apprehension revealed by GUDs (Dall et al 2001;Kotler et al 2010).…”

“…(iv) Moon phase: I assessed all three factors during the full moon (risky) and subsequent new moon (less risky). Snowshoe hares combat reduced winter survival during the full moon (Griffin et al 2005) by occupying dense and putatively safer habitats (Gilbert and Boutin 1991;Gigliotti and Diefenbach 2018), but not in all studies (e.g., Griffin et al 2005).…”

“…1d). Even so, net risk typically intensifies for nocturnally foraging prey as the moon waxes towards full (Gilbert and Boutin 1991;Kotler et al 2010;Gigliotti and Diefenbach 2018), so hares were more vigilant at stations where traversing the open habitat took them far from safety ( Fig. 1a) and made them more visible to predators.…”

“…The existence of multiple options, and their dependence on numerous features of the foragers and their environment, suggests flexible foraging strategies that are contingent on the temporal and spatial dynamics of risk (Gigliotti and Diefenbach 2018). If we are to test underlying theory, sort through the many possible ways that different behaviours might interact (Kotler et al 2016), and evaluate why they do or do not change through time, then we need replicated studies that measure multiple risk-reduction options (e.g., Altendorf et al 2001).…”