Experimental trials of the northern flying squirrel (Glaucomys sabrinus) traversing managed rainforest landscapes: perceptual range and fine-scale movements

Abstract

Successful dispersal in many species may be a function of the distance at which animals can perceive a particular landscape feature (i.e., perceptual range), as well as energetic costs associated with traversing the distance towards that feature. We used a model, relating perceptual range to body size of mammals, to predict the perceptual range of the northern flying squirrel ( Glaucomys sabrinus (Shaw, 1801)) in fragmented forests of Southeast Alaska. We hypothesized that the perceptual range of flying squirrels would be 325.5–356.5 m in clearcuts and 159.7–174.9 m in second-growth stands. The distance advantage in clearcuts may, however, be lost if the cost of transport in that habitat is higher. Our results suggest that as heuristically predicted by the model, the perceptual range of flying squirrels was greater in clearcut habitats than in second-growth stands. Nonetheless, for both habitats the actual perceptual range was significantly shorter than predicted by the model. We found that precipitation, and associated cloud cover and illumination, and wind speed, which affect olfaction capabilities, influenced orientation success. Although squirrels more often oriented towards the forest edge in clearcuts, they paused more often during their movements, which may lead to higher costs of dispersing through this habitat. The application of the mass-based model to nonagricultural landscapes should be done with caution, and variables such as wind and illumination be measured concurrently. Our data illustrate that dispersing squirrels likely will not venture into managed habitats because logging creates clearcuts larger than the perceptual range of these mammals.