Are Green Anoles Disappearing From Florida?

By Karen Tremmel, Thursday, Sept. 11, 2008
Tampa Bay Newspapers on-line Edition

How beautiful it is to watch the dazzling, emerald green anole bask in the morning sun upon the back gate.

A couple of weeks ago I was by mere chance afforded the opportunity to shoot firsthand snapshots of the mating of two green anoles in my garden.

Fortunately I had a long lens close by which provided me some comfortable distance from the amorous pair. They seemed to pay me no mind as I snapped away, eager to capture the ardent moment on film.

The green anole, Anolis carolinensis, is the only official native member to the vertebrate genera in Florida. Expressing concern, TBN readers have written Back to Nature inquiring about the scarcity of green anoles at play in their gardens. „In the past when I worked in my garden I would always see the little green lizards upon the garden wall playing and sunning themselves. Now all I see are those ugly brown things,‰ one reader wrote.

While researching I found several reports pointing to the dominance of the nonnative brown anole, Anolis sagrei over the green Anolis carolinensis. Although there does seem to be evidence that there are less green anoles today than in the past some research indicates that brown anoles may not actually be the main culprit for the decline in their populations. In fact, there are areas where green anoles are dominant over brown anoles.

How can someone distinguish between a green and a brown anole?

For identification purposes: Green anoles can turn brown, but brown anoles are unable to turn green. Brown anoles can turn darker brown and even black. Brown anoles have strong markings down their backs. Green anoles have a bright blue eye ring while in their green color change and their dewlaps are a quieter shade of burgundy.

Brown anoles naturally display near ground level, moving back and forth, up and down while showing off their bright orange dewlaps to impress other males. Green anoles prefer higher and more secretive perches out of the way so, in fact, they may not actually be as visible.

One aspect that may play in the decline of the green anole is competition for food. In a report by J. Masterson of the Smithsonian Marine Station: „In areas where this exotic species (brown anole) has become established, it is very often the most abundant reptile species present. Anolis sagrei is among the most abundant lizards throughout Florida ∑ ‰

The first anecdotal suggestions implicating the exotic brown anole in the decline of native green anole populations in Florida were published in the 1960s (Collette 1961, King and Krakauer 1966). Direct studies of interspecific associations between the two congeners appear much less significant than interspecific (within-species) competitive interactions within these aggressive, territorial animals (Brown and Echternacht 1991).

Field observations and experimental manipulations have demonstrated that brown anoles in Florida prey directly on other small vertebrates including hatchlings of the native green anole.

Another factor noted: brown anoles simply multiply more prolifically than green anoles. Green anoles typically reproduce during the months of April through July when levels of sex steroids and behavior are maximal.

And yet one more intriguing explanation attributed for the brown anole‚s high profile in the garden as opposed to the secretive green anole: The brown anole prefers to display conspicuously low to the ground, under foot, to be exact. They seem to run from every corner as we walk along a path. They posture from lamp posts, leafy plants, picnic tables, the handle of a shovel or atop a garden statue.

Brown anoles are quite visible. As a result this also renders them easy targets for roaming predators such as large birds and cats. House cats are one of the lizard‚s most formidable foes. House cats (a nonnative species to North America and unnatural predator) are frequently left to roam backyard gardens at their leisure to hunt down prey such as native birds and lizards. Once a cat becomes adept at capturing the conspicuous brown anole the cat may turn predatory interest to capturing the more secretive green anoles. Since the green anoles do not breed as prolifically as the brown anoles, the green anoles are killed off and the more heavily populating brown anole survives to be seen.

Reptiles have been evolving on our planet for more than 300 million years so the causes of a species‚ decline are often more complicated than the apparent obvious theory. However, we have discovered with a wide variety of plants provided in the garden, the lack of pesticides, in conjunction with the scarcity of nonnative predators roaming freely in the garden, the green anole seems to be living and reproducing naturally here, perhaps even making somewhat of a comeback. For now we‚re waiting in anticipation for the prodigies of these two lovely, charismatic gems to beautify the garden in jeweled sunbeams on another summer‚s day ∑ back to nature.

Are they disappearing? Good question. I just returned from Florida, and like in former visits, it was hard to find one green anole in Central Florida. The introduced Brown anoles are everywhere...

I've had long discussions about this issue with a close friend who lives in Florida. His theory is more displacement by sagrei than replacement. Sure enough, after looking up in the brush, walls etc., the greens are still there. They have just moved higher. Whether or not this makes them more vulnerable to avian predation etc. remains to be seen.