Overwater Movement of Raccoons (Procyon lotor) in a Naturally Fragmented Coastal Landscape

Abstract

Procyon lotor (Raccoon) is a major predator of beach-nesting and colonial waterbirds on the Virginia barrier islands. An understanding of water as a barrier to inter-island movement by Raccoons will be essential to effective management of these predators in this naturally fragmented coastal environment. We examined 4 independent lines of direct evidence for Raccoon movement between 1999 and 2007: 1) locations of recaptured, ear-tagged Raccoons on both the islands and the adjacent mainland, 2) overland movements of radio-collared Raccoons, 3) inter-island movements of radio-collared resident Raccoons, and 4) movements of translocated Raccoons. We recaptured 78 of 177 ear-tagged island Raccoons, all on the same island as the initial capture. We also tagged and released 65 mainland Raccoons, none of which was ever recaptured on an island. We often observed overland movements >1 km per day by radio-collared animals on both the islands and the mainland. Nevertheless, only 3 of 51 (6%) collared animals (2 males and 1 female) moved overwater from the location where they were captured. None of the 4 Raccoons radio-collared on the mainland moved to an island. Although Raccoons in this system are highly mobile, overwater movements seem to be infrequent events; only 3 of 234 tagged/ collared island individuals moved between islands, and none of the 69 tagged/collared mainland individuals moved to an island. Finally, we observed return movements by 22 of the 32 (69%) animals (11 males and 11 females) that were translocated either from the mainland to a nearby island or between adjacent islands. Translocated animals exhibited a much greater tendency than resident animals to make overwater crossings. In all cases of overwater movement, the water channels were relatively shallow and relatively slow moving. None of the 335 marked animals in this study crossed a tidal inlet. The mobility observed here is consistent with the idea that the distribution of Raccoons on the islands has expanded in recent decades. Predation management on these islands will require a strategic approach that takes into account both island isolation and Raccoon mobility.