Vesa Selonen

Theoretically, dispersers should target the habitat where prospects for fitness will be highest. Aiming for a habitat similar to the natal area (natal habitat-biased dispersal) has been hypothesized as a probable rule of thumb for dispersers, but has received very little empirical support to date. We investigated similarities between natal and post-dispersal settlement sites with radio-collared Siberian flying squirrels (Pteromys volansL.). Juveniles born in small patches and raised in nests close to patch edge settled in small patches and used nests close to edges after dispersal. In addition, post-dispersal use of dreys (versus cavities) was similar to that observed in natal sites. However, the quality of settlement habitat was unrelated to the quality of the natal site, which suggests that natal experience on average-quality habitats may not lead to ecological traps for flying squirrels. This study provides evidence that habitat selection at the landscape scale is influenced by habitat of natal area.

Dispersal is a key determinant of the population dynamics of species. Thus, a better understanding of how dispersal is affected by the landscape structure and how animals make decisions about moving across different landscapes is needed. We studied the dispersal of 60 radio-collared juvenile Siberian flying squirrels (Pteromys volans) in southern Finland. The effect of landscape structure on selected dispersal direction, dispersal distance, and straightness of dispersal path was studied. Flying squirrels were capable of dispersing over long distances in fragmented forest landscapes. The patches used as temporary roosting sites during dispersal were of a lower quality than were those used as finally occupied patches. The patches used were larger than were patches on average in the study areas. There was a very clear directional bias in the dispersal path (i.e., it was nearly a straight line), which remained over a large scale, but wide-open areas obstructed the straightness of the path. As the distances between crossed patches increased, short-distance dispersers were found further away from their natal home range. However, there were no differences in the landscape that could explain the differences between individuals in decisions to remain philopatric or to become short- or long-distance dispersers. In addition, whereas short-distance dispersers dispersed in random directions, long-distance dispersers started to disperse in directions dominated by preferred habitat. Thus, there were behavioral differences between dispersers. Our results supported the hypotheses stating that individuals decide to disperse long or short distances before the onset of dispersal.

Elements of the landscape, such as patches of preferred habitat, matrix between patches, and corridors linking patches, differ as movement habitat for animals. To understand how landscape structure influences the movement and thus, population dynamics of animals, clear empirical knowledge on patterns of movement is needed. The Siberian flying squirrel inhabits spruce‐dominated boreal forests from Finland to eastern Siberia. Numbers of flying squirrels have declined severely in Finland in past decades, probably due to modern forestry. We studied the movement of radio‐collared adult flying squirrels in preferred (spruce forest) and in matrix habitat (open areas and other habitats with trees) in Finland 1997–2000, and determined whether the woodland strips connecting patches of preferred habitat could function as ecological corridors for flying squirrels. Flying squirrels used woodland strips for inter‐patch movements, but also used matrix with trees and were able to cross narrow open gaps. Males moved longer total distances and crossed edges more often than females. Males used matrix habitats for movement between spruce patches, and moved faster and more directly in the matrix than in the spruce forest. Females seldom changed spruce patches, but instead used the matrix for foraging. For both sexes probability of leaving the spruce forest patch correlated negatively with the size of the patch, but the type of connection the patch had to other patches did not affect the leaving probability. Due to efficient movement abilities of the flying squirrel and forest‐dominated landscape structure of southern Finland, we suggest that conservation acts for maintaining viable populations of flying squirrels should focus on the quality of managed forest and the area of suitable breeding habitat (i.e. on habitat loss), but not necessarily on ecological corridors.