Italian lizards invade Greenwich, CT – via Herp Digest

Greenwich Time, By Peregrine Frissell, Sunday, July 24, 2016

GREENWICH — Non-native Italian wall lizards have begun to appear in town, according to a Harvard researcher who says they may be riding the Metro-North train into Fairfield County.

Harvard post-doctoral fellow Colin Donihue has been studying their migration and plans to return to Greenwich next month as he tries to solve the mystery of how they got here and how they are surviving in a much cooler climate than they are used to.

There has been a population living in Bronx, N.Y., since a pet truck crashed and led to their escape to the urban wild in the 1960s, Donihue said. He it’s possible this population has spread north using the Metro-North train lines.

“It’s a really nice expressway for them to travel distances,” Donihue said. “Those little guys move pretty fast.”

He said the loosely packed stone beneath the tracks provides good shelter from predators and easy access to backyards full of insects and warm laundry ducts.

“It seems these little Italian wall lizards are really making use of human heat sources in order to make it through the winter,” Donihue said. “It’s also great habitat to hide from predators.”

Another explanation could be that an area resident went on vacation to Italy, where they are very common, and brought some back to live in their garden, Donihue said. He said there are populations in Kansas and Los Angeles that are known to have started that way.

He has sent tissue samples to geneticists at the University of California-Merced to see if the lizards, which are harmless to humans and pets, found in Greenwich are related to those from the Bronx.

Donihue is trying to find more specific information about the migration patterns of these lizards. He has considered trying to put GPS chips on them like people do with their pets or larger wild animals, but all the current models are too large for the small, 4-inch body of the lizard to handle.

He has seen some backyards with as many as 15 to 20 lizards, which leads him to suspect the entire Greenwich population is in the hundreds, but somewhere shy of 1,000. Donihue said he first needs to figure out how far from the tracks they have strayed to determine a more accurate population estimate.

He is also trying to determine if they have reached beyond Greenwich’s border into Stamford.

Donihue’s research is focused on how animals adapt to live in human landscapes. He has been studying a sister species of the lizard in Greece for the past five years, and is interested in discerning how the Connecticut lizards are changing to thrive in such a different environment.

“It would feed into this bigger question of what makes an invasive species successful, and how can we understand how those species are evolving to live side-by-side with humans,” Donihue said

He believes their metabolisms are slowing down and becoming better regulated than their relatives in Greece and Italy to adjust to the cold, but he doesn’t think that’s the only thing allowing them to expand this way.

“We’re starting to talk about animal personalities, so maybe these lizards right at the invasion front are more risk-taking or interested in trying out new types of food or exploring different areas,” Donihue said.

The only lizard native to Connecticut is a skink, which has a blue tail that is much longer than the Italian invaders, which tend to be greener in color.

Greg Watkins-Colwell, collection manager at the Peabody Natural History Museum at Yale University, has worked in the field locating lizards with Donihue.

He said Donihue first learned about the lizards when someone posted a picture of one on Facebook.

“It’s one of those odd things where social media actually made a difference,” Watkins-Colwell said.

Watkins-Colwell isn’t sure how far north the species will reach, but the rest of the communities along Metro-North could be fair game.

“It kind of makes sense for a lizard that is adapted to live on stone walls and archeologic ruins to use what is effectively a pile of rock as its habitat,” he said. “It’s interesting from a conservation perspective, because you can predict where they will be. You can start watching for them up the line.”

If you have seen a wall lizard, contact Donihue at colin_donihue@fas.harvard.edu.