Invasion of the wall lizards: They are beyond eradication on Island

They are crawling all over Saanich and Victoria, in thick bunches on the Peninsula and in Langford. They’ve been spotted in Metchosin. There are large populations in Shawnigan Lake and Nanaimo and they’ve even been seen as far north as Campbell River.

Now they have made the move to Salt Spring and Pender islands.

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Wall lizards — native to temperate climates like Italy around the Mediterranean — have been on the move on the Island since they were first set free from a roadside Central Saanich zoo more than 50 years ago.

They’re so numerous in the capital region and other parts of the Island now that eradication of the invasive species is “impossible,” says a scientist tracking the scaled reptiles.

Gavin Hanke, curator of vertebrate zoology at the Royal British Columbia Museum, now estimates the Island population of the common wall lizard at between 500,000 and 700,000.

“They’re like dandelions … they just keep popping up everywhere,” Hanke said in an interview.

Wall lizards thrive in urban, man-made environments such as gardens, rock walls, wood piles and fences, and are often spotted soaking in sunshine on paving stones and rocks.

They are excellent climbers and move very quickly, fanning into new neighbourhoods and communities every year.

Eradication of the species should have started decades ago, Hanke said. But now, as populations scurry higher, it’s down to attempts at tracking and controlling their spread.

Wall lizards have spread across Europe from England to Turkey. Introductions into North America have now included high concentrations in Ohio, Kentucky and Indiana, said Hanke

Male wall lizards have black and green spots. Females are a little less flashy — they’re grey-brown with light green specks.

Hanke said there isn’t much known about the harm wall lizards are causing to the Island’s natural environment, but there is evidence they are eating pollinating bees and dining on young garter snakes.

Hanke also has fears they are preying on young sharp-tailed snakes, which are native and endangered.

The Habitat Acquisition Trust said the wall lizard also competes for food and shelter with sharp-tailed snakes and the native northern alligator lizard, which have fewer young over the course of a year and a smaller range for food sources. Both wall lizards and sharp-tailed snakes are egg-layers, and competition for nest sites is possible, the trust said in a report.

Hanke said northern alligator lizards bear their offspring live, and wall lizards could be eating those young because they are already known to eat their own.

Hitching a ride with humans

The wall lizard’s propensity to eat their own young may also explain the fast spread of the species, as juveniles quickly move into new areas to save their own skins.

The proliferation of the wall lizard on Vancouver Island, areas of the Fraser Valley and now the southern Gulf Islands has occurred with the helping hands of humans, says Hanke.

He said it’s sometimes intentional — children often take them home as pets — or they are hitchhikers in camping gear, loads of firewood and hay bales, livestock trailers and eggs left in plant pots.

“If you move wall lizard eggs by accident, you can have five to 10 wall lizards right away,” said Hanke. “If it’s a long, warm summer, a female can have two clutches a year. In some places, three a year have been reported.”

The B.C. Invasive Species Council said without human assistance, wall lizards typically spread at a rate of about 100 metres per year, so human assistance is helping to increase the lizard’s range by catching rides on vehicles, shipments of produce and plants or released by people who keep them as pets.

Wall lizards are omnivorous, feeding on a variety of insects, spiders, and other invertebrates, as well as fruits. They can reproduce up to three times per year during the spring and summer. The eggs are carefully hidden under rocks or pieces of wood on the ground, where they incubate for up to a month before hatching.

Where it all began

Hanke said the epicentre of the wall lizard explosion was a small private zoo in central Saanich on the road to Butchart Gardens. He traces the release — either intentional or by accident — of about a dozen wall lizards to around 1967. Rudy’s Pet Park closed in 1970.

The Habitat Acquisition Trust said for decades, the lizards were restricted to a small area around Brentwood. “Since the 1990s, they have spread at an alarming rate, raising concerns about their impacts on native species,” it said.

Their numbers exploded quickly on the Saanich Peninsula up to Sidney and Swartz Bay and eventually spilled into Saanich. The lizards are established on the West Shore and there are pockets of them in Shawnigan Lake, Mill Bay, Denman Island and almost every community south of Campbell River.

“They’re all over Saanich and Victoria, and just crawling in Langford,” said Hanke. “We’re seeing them in Metchosin now. There’s been a large population in Nanaimo since 2012. We have records of them in Campbell River, but we’re not sure if they are establishing there because the winters tend to be longer with more rain.”

Hanke, who lives in the Cedar Hill area of Saanich, says it’s not uncommon for him to see several wall lizards in his yard every day.

He said people he’s spoken are in favour of killing them, but there are others who want to let the lizards be.

“I know a guy who was catching five pounds a week on his property, and it never depleted the population,” said Hanke.

He said some properties he’s visited are so infested that he has caught a lizard a minute.

The new reported discoveries on Salt Spring Island were in the Fulford-Ganges and Vesuvius roads areas. On Pender Island, he said, the wall lizards have been reported at the Medicine Beach Nature Sanctuary on North Pender.

Hanke said it is essential to eradicate the lizards early in places like these before they can spread and establish themselves.

A wall-lizard buffet

The next phase of his research is to determine what is preying on the lizards.

Initial evidence is that house cats are killing the lizards. Raccoons have also been observed turning over rocks at night to eat them. There is also evidence that Great Blue Herons, crows and songbirds are developing appetites for the wall lizard, and spiders are dining on their young.

“It looks like there are a lot of predators, but they’re not keeping up,” said Hanke.

The Habitat Acquisition Trust also said wall lizards can reach high densities in suitable open or semi-open habitats, raising concerns about ecological impacts on woodland habitats, especially Garry oak ecosystems.

There is no government management plan for the wall lizard, said Hanke. The only thing people can do is report them in an attempt to control their spread.

To report a sighting, go to inaturalist.org. The site allows you to upload images and provide location details.

Hanke said he is monitoring the site.

People can also report the lizards to the B.C. Invasive Species Council at bcinvasives.ca.

dkloster@timescolonist.com

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