DO LIZARDS HIBERNATE?

by Whit Gibbons

November 27, 2005

The following are answers to several questions I have been asked recently about a common lizard of the Southeast, called green anoles by some people and American chameleons by others.

Q. I live in northern Alabama and recently saw 15 lizards (the chameleon type that change from brown to green and back) in the yard, and my husband wanted to know if there was some kind of food we could put out for them this winter. Also, do these lizards hibernate?

A. Yes, green anoles hibernate in colder regions of their geographic range, which includes the Carolinas, southern Tennessee to Arkansas and east Texas, and throughout the other Gulf states. They often hibernate in large groups and were probably congregating in late fall before it turned cold. Anoles spend winter under bark, inside rotten logs, or under boards of houses and barns. They can be seen on some bright, sunny days in winter, basking in the sun. As far as feeding them, they will do fine with no help from us as they eat little or nothing in winter. When spring arrives, they will begin feeding on small insects and spiders around the yard.

Q. I have noticed that the lizards around our yard in South Carolina are sometimes brown, or even gray, and sometimes brilliant green. I thought the lizards that changed colors were chameleons that mimicked the color of the object they were on. But I recently saw a green one sitting on a brown branch and on another day saw a brown one on some green vegetation. What gives?

A. The brown/green color changes of the green anole are not simple. Part of the confusion is because they are in a completely different family of lizards from African chameleons, which change color based on their substrate and background, creating a true camouflage. Color change in green anoles, however, is a response to other factors such as temperature and humidity and can also be influenced by their hormonal or emotional state. Being threatened by a predator, being challenged by another anole, or even increasing their level of activity can result in color changes. Most anoles hidden under bark or leaves in late fall and winter will be brown, whereas they usually turn green if they bask in the sun. However, as far as I know, scientists do not understand all the factors that make a green anole change color. Sounds like a worthwhile science fair project.

Q. We were wondering if the warmer winters we have had in Georgia the past few years could have produced an increase in the number of anoles we find around our house and yard.

A. Warmer winters could possibly result in more insects for anoles to eat in the spring, which could lead to an increase in reproduction in the species, and therefore more lizards. However, determining the exact cause of an increase or decrease in the population numbers of animals is extremely complex, even for population ecologists who study a particular species in a prescribed area. Part of the problem is the difficulty of differentiating whether an observed effect (such as change in population size) is the direct result of weather or climate changes that affect the animal itself or are an indirect result of an effect on another species (such as a parasite or predator) that might control population size. In addition, some changes in numbers of an animal species, even over a several-year period, may simply be coincidental with an observed environmental change that is unrelated to the species.

Q. Why do the lizards we see that can change from brown to green sometimes have a bright red throat?

A. Male anoles use a throat fan, or dewlap, to challenge other males, and sometimes even people. The dewlap is typically bright red in the native anole and is yellow, orange, or a combination of colors in some of the introduced anoles now found in southern Florida. The display of the dewlap is often accompanied by the male lizard doing push-ups and bobbing its head. Next time you see one with a red throat, watch the performance.



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