Population profile of an introduced species, the common wall lizard (Podarcis muralis), on Vancouver Island, Canada

Abstract

Introduced species represent one of the greatest potential threats to persistence of native species. Therefore, it is important to understand the ecology of introduced species in order to develop appropriate mitigation strategies if required. In this study, using data collected in 1992–1993, we describe some fundamental population attributes of common wall lizards, Podarcis muralis (Laurenti, 1768), of Italian origin, introduced near Victoria, British Columbia, in the early 1970s. Male and female wall lizards reached similar snout–vent lengths, but males had relatively longer tails and were heavier. However, when gravid, females attained a body mass similar to that of males of equal snout–vent length. We found gravid females in all months from May to July, inclusive, but hatchlings did not appear in the field before late July. Growth rate was inversely related to body size, and lizards probably reached maturity in their second full summer. Larger lizards were more likely than smaller lizards to have experienced tail loss prior to capture, but the probability of tail loss upon capture was higher for smaller lizards than for adults. Our results suggest no fundamental differences in population characteristics between P. muralis on southern Vancouver Island and populations at sites within the species' natural range in Europe. Whether P. muralis on Vancouver Island is a threat to the native northern alligator lizard, Elgaria coerulea (Wiegmann, 1828), remains an open question.