Natural disturbances shape wildlife habitats by altering patterns of resource distribution and abundance as well as predation risk. Eastern North America’s boreal forests are characterized by the predominance of late-successional stands driven by gap-phase dynamics, due to forest fire cycles exceeding 200 years. Regeneration within canopy gaps may create conditions suitable for species associated with early-successional forests, such as snowshoe hare. The use of gaps, however, may entail a trade-off between access to forage and increased risk of predation. The nature of this trade-off should be gap-size dependent, as predation risk generally increases with distance from cover. According to principles of optimal foraging theory, an animal should leave a food patch when the benefits of remaining in the patch no longer outweigh the costs. Giving-up densities at experimental food patches can be used to measure changes in a forager’s perception of predation risk. We assessed the snowshoe hare’s perception of predation risk using the diameter at point of browse (DPB) of jack pine boughs as a measure of giving-up density. We predicted that hare would clip boughs to larger diameters under forest cover than within gaps, and that DPB would decline with increasing distance from cover within the gap. Boughs were placed along a transect extending from the center of canopy gaps into adjacent forest cover in 88 gaps.
Results/Conclusions
Hare clipped boughs to larger diameters under forest cover, indicating that forest cover was perceived as safer than canopy gaps. Furthermore, the probability of use of boughs within gaps decreased with distance from the gap edge. Consistently, movement analysis of winter trails showed that hare increased their speed when crossing areas with reduced cover. Our study demonstrates how gap-phase dynamics structure the spatial organization of snowshoe hare by influencing the trade-off between access to food and predation risk.
