Invasive wall lizard seen on Salt Spring Island
An invasive lizard species that has over-run gardens from Sidney to Colwood is confirmed to have made landing on Salt Spring, and officials are asking members of the public to help keep tabs on the situation.
Channel Ridge resident Pat Miller discovered the first known instance of the common wall lizard on Salt Spring, which has been confirmed by the Royal BC Museum’s curator of vertebrate zoology, Gavin Hanke. Miller said she first noticed the reptile outside her home last year but thought it might have been a native alligator lizard. When it reappeared this spring, though, she had done some more reading and suspected it was an invasive native to Italy.
“I’m a retired biologist. I’m just interested in what creatures are out there,” Miller explained.
Miller took a photo of the lizard and posted it to iNaturalist for identification. She also sent photos directly to Hanke, who has written several journal articles on the topic. She’s now trying to capture the lizard to send it to him.
Common wall lizards were introduced to the Saanich Peninsula in 1967 when a private zoo shut down and the owner released around a dozen of the reptiles into the wild. There are now an estimated 700,000 in the area, and there are known populations in Duncan, Crofton, Nanaimo, Denman Island, Courtenay and Campbell River.
“I kind of expected [them to appear on Salt Spring] since you’re so close to Vancouver Island and they’re super abundant on Vancouver Island. I’ve actually been kind of dreading it,” Hanke said.
In Hanke’s own neighbourhood, every garden has at least 10 resident wall lizards, and he knows of one neighbour nearby who has something like 200. He said the wall lizard is well-adapted to the local climate since it’s very similar to its native Italy, and Salt Spring is especially ideal because it favours garden structures, rock walls and open sunny areas.
“This region is just so hospitable. The winters are short and mild and the summers are warm, and with climate change it’s just going to get worse,” he said.
Although many native species as well as domestic cats prey upon them, wall lizards are such prolific breeders predation can’t keep the population down. Native alligator lizards only hatch young once per year, but wall lizards have at least two clutches and sometimes three, with five or more eggs per clutch. Once hatched, the hatchlings scatter wide to avoid being eaten by their parents.
On the flip side, wall lizards are fearful predators in the own right, and they target everything from native snake and lizard hatchlings to important pollinators. There is concern about local ecosystems due to the large number of insects they eat, and for rare or endangered species like the sharp-tailed snake.
Wall lizards may appear similar to alligator lizards, especially as juveniles when they are a coppery brown. As adults, though (usually around 15cm but up to 21 centimetres from nose to tail), wall lizards are distinct for their green and black patterning and for having scales that are almost too tiny to see with the naked eye. Another difference is that wall lizards scurry away quickly if approached, while alligator lizards tend to let people get closer, and wall lizards like more sun while alligator lizards can tolerate spending a lot of time in the cool forest.
So far Miller has seen just the one invader, but islanders are being urged to watch out for others.
“My feeling is it would be pretty unlikely that I was the only person on Salt Spring with a wall lizard,” Miller said.
Hanke encourages people to take photos if they see a lizard. Those photos can be uploaded to iNaturalist and sent to him directly at firstname.lastname@example.org.
Once properly identified, capturing wall lizards may be possible using a noose on the end of a long stick. Hanke recommends people put lizards in a tub in the refrigerator to send them into hibernation and then finish them off in the freezer once they’re asleep.
Since the B.C. coast is so hospitable to so many species, Hanke additionally urges people never to release pets or fish into the outdoors if they can no longer care for them. They should be re-homed, or if that’s not possible, brought to a vet to be euthanized.
“There’s still a lot of things in the pet trade that could get established here and we’re just lucky they haven’t been released,” Hanke said. “The pet trade is a great vector for exotic species and it’s a great threat.”