Road and topography effects on invasion: edge effects in rat foraging patterns in two oceanic island forests (Tenerife, Canary Islands)

Abstract

We studied the effect of road edges on foraging activity by introduced ship or roof rats Rattus rattus in road-fragmented laurel and pine forests on Tenerife (Canary Islands). By using selective baited stations enabling only foraging by rats we assessed bait removal rates along a road-interior gradient and different topographic locations. We recorded higher removal rates in the laurel than in the pine forest regardless of the distance to road. We detected an edge effect of paved roads on introduced rat foraging. Removal rates were significantly greater along road edges than in forest interior in the laurel forest but not in the pine forest. Rats were more active along road habitats in forest ridges and slopes than in ravine beds in the laurel forest. There was no difference between topographic locations in rat activity at any distance from the road in the pine forest. It is suggested that variation in foraging intensity by introduced rats in road-fragmented forests on these islands may depend, among other factors, on forest type, road edge effects and topographic pattern of the landscape.