THE EFFECTS OF HABITAT FRAGMENTATION BY FORESTRY AND AGRICULTURE ON THE ABUNDANCE OF SMALL MAMMALS IN THE SOUTHERN BOREAL MIXEDWOOD FOREST

To determine the effects of forest fragmentation on the abundance of s mall mammals, we livetrapped at edges and in the interior of forest pa tches in contiguous, logged, and agricultural landscapes in the southe rn boreal mixedwood forest of Saskatchewan. From 1994 to 1996, we capt ured 1548 small mammals (11 species) during 8172 trap-nights. The abun dance of all small mammals combined was lower in forest patches isolat ed by logging than in contiguous forest or farm woodlots surrounded by agricultural land. This pattern was consistent in all years, despite significant annual fluctuations in numbers of the boreal red-backed vo le (Clethrionomys gapperi), one of the most abundant species in our st udy area. Red squirrels (Tamiasciurus hudsonicus) and northern flying squirrels (Glaucomys sabrinus) were more abundant in farm woodlots. Th e abundance of deer mice (Peromyscus maniculattus) was significantly l ower in forest patches surrounded by clearcuts, and we speculate that they may have used clearcuts more than forest patches. In contrast, th e numbers of boreal red-backed voles were similar among landscapes. Th e only species showing a response to edge was the deer mouse, which wa s significantly more abundant at edges of farm woodlots than in interi ors. We also found no significant difference in abundance of any speci es between small(10 ha) and large (>20 ha) farm woodlots. For most spe cies, within-landscape attributes such as edge and patch size seemed t o have little effect on their abundance. However, for a variety of rea sons, small-mammal numbers seem to vary considerably among forest patc hes in different landscapes.