Habitat loss and sometimes habitat fragmentation per se affect species survival, reproduction, dispersal, abundance and distribution. However, understanding the independent effects of fragmentation (i.e., landscape configuration) has been limited because it is frequently confounded with landscape composition (i.e., habitat amount). We assess the independent effects of landscape composition and configuration on the occurrence of northern flying squirrels (Glaucomys sabrinus) in New Brunswick, Canada after controlling for local site conditions. We measured landscape structure using an ‘‘organismbased’’ approach; landscape structure was characterized quantitatively using a spatially explicit localscale distribution model for northern flying squirrels. Flying squirrels occurred more frequently in old forest, at sites with mixed coniferous–deciduous microhabitat composition and greater amounts of habitat cover at the neighbourhood (within homerange) scale. Squirrels were less likely to occur at sites surrounded by greater proportions of non-habitat matrix (non-treed or early seral open areas). The occurrence of flying squirrels was not strongly correlated with patch size or edge contrast. We detected no interaction between the effects of patch size and habitat composition. Landscape composition was clearly a more important predictor of flying squirrel distribution than configuration. We conclude that management practices that maximize the amount of old forest cover, maintain diverse tree species composition and minimize the creation of open areas should enhance the conservation value of landscapes for northern flying squirrels. Manipulating landscape pattern though forest management likely has limited use in mitigating the negative influence of habitat loss on this species.

Landscape structure Habitat loss Fragmentation Acadian forest Spatial modelling Scale Glaucomys sabrinus