by Whit Gibbons
November 27, 2005
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.
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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