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

We studied the effect of road edges an foraging activity by introduced ship or roof rats Rattus rattus in road-fragmented laurel and pine forests on T enerife (Canary Islands). By using selective baited stations enabling only foraging by rats we assessed bait removal rates along a road-interior gradi ent and different topographic locations. We recorded higher removal rates i n 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 alon g road habitats in forest ridges and slopes than in ravine beds in the laur el forest. There was no difference between topographic locations in rat act ivity at any distance from the road in the pine forest. It is suggested tha t variation in foraging intensity by introduced rats in road-fragmented for ests on these islands may depend, among other factors, on forest type, road edge effects and topographic pattern of the landscape.