by Whit Gibbons

May 18, 2014

Milan, Italy, and Cincinnati, Ohio, are seldom mentioned in the same sentence. One reason to do so is that both are home to a reptile known as the common wall lizard.

In books about U.S. lizards, the wall lizard has become a standard entry because it's become naturalized, meaning it is a non-native species that is reproducing successfully and maintaining sustainable population levels.

Wall lizards arrived on the North American continent more than 60 years ago. They thrive on outdoor walls of brick or concrete with plenty of crevices, presumably a preadaptation from living in rocky habitats of cliffs and boulders in their native range of southern Europe.

They are handsome creatures, reaching lengths of over 9 inches from nose to tail. Like many birds, the males become more brightly colored during the mating season, displaying a row of bright blue spots down their sides.

Cincinnati's local habitat is perfect for the wall lizards; so is the climate. Milan and Cincinnati could use the same weather map much of the year as daily and seasonal temperatures, rainfall, and humidity are similar.

When wall lizards arrived in Cincinnati they may not even have known they had left Italy. As often happens with invasive species, they could have become exceedingly unpopular with local residents.

But according to an upcoming publication by Jeff Davis, wall lizards "are beloved creatures, and (the residents) enjoy seeing them scurry about their landscape." Jeff is an Ohio herpetologist who has done more research and is more knowledgeable about the species than anyone else I know.

Recently, I talked with Jeff about wall lizards. The most plausible story of how a European lizard made its way to Ohio involves a boy named George Rau, who returned home to Cincinnati from a vacation in northern Italy in the early 1950s.

Like many another youngster of that era, George collected critters. While he was on vacation in Milan, he caught some lizards that were common in the area.

Turns out he brought 10 of them home with him. He released them in his Cincinnati neighborhood, which proved ideal habitat because of the stacked rocks and brick retaining walls in the hilly residential areas.

Jeff says wall lizards probably number in the hundreds of thousands today in densities as high as 1,500 per acre in some areas. How an animal survives and how widespread it becomes in a region depends on a variety of ecological factors.

What kills it and how it disperses over the landscape can be critical. Cats and cars are primary sources of mortality. Nonetheless, although wall lizards are subject to the same hazards as other wildlife when crossing streets, they are apparently expanding their geographic range beyond Hamilton County.

They have been documented in another county in Ohio as well as south to Kentucky and west to Indiana.

Jeff and his colleagues have confirmed the presence of wall lizards in more than 100 localities and investigated how they might have gotten to various places. Some undoubtedly have been carried to other areas on purpose or as stowaways.

The fact that several survived transport from Italy to Ohio attests to their hardiness, so taking a trip of a few hours in a vehicle should be no problem. He also has a record of individual lizards sitting on logs that floated down rivers.

Smaller wildlife often disperse unintentionally during such rafting adventures and end up downstream, far from their point of origin.

Not all introduced species become hardcore invasive pests that cause problems for other wildlife. Most are probably inconsequential and are never heard from again after a brief visit as a tourist.

Some, like honey bees, camellias, and wall lizards, have even earned stellar reputations. They not only do no harm to local wildlife, they have become species that people actually want to have around.

Looks like wall lizards will soon offer themselves up to become "beloved" in communities far away from the hillsides of Cincinnati.

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