RECENT RAPID EXPANSION OF COMMON WALL LIZARDS (PODARCIS MURALIS) IN BRITISH COLUMBIA, CANADA

Abstract

The Common Wall Lizard (Podarcis muralis) has existed in southwestern British Columbia since 1967, but expanded its range rapidly in the last decade. In 2006, P. muralis was thought restricted to 4 populations on southeastern Vancouver Island: 3 on the Saanich Peninsula and 1 in the Triangle Mountain area. However, increased reporting and exploration led to the recognition that these populations have merged. Further, P. muralis have also appeared along the eastern side of Vancouver Island north to Campbell River; and on Denman Island. In 2015, P. muralis was also reported from two BC mainland locations: Osoyoos in the southern Okanagan, and the city of Vancouver. Introduced lacertid populations are reported to spread from their points of origin at a relatively slow rate (∼1 km every 10 y), so given that P. muralis has been found at least 200 km north, 300 km west, and from Vancouver Island to Denman Island and the British Columbia mainland over the last 52 y, human-assisted dispersal likely contributed to its apparently rapid radial expansion in southwestern BC. As they expand into rural and protected areas on Vancouver Island, P. muralis may have increasing opportunities to interact with the native Northern Alligator Lizard (Elgaria coerulea). Where E. coerulea and P. muralis coexist on southern Vancouver Island, the latter seems more abundant, which raises concern and warrants study.