Originally published on August 1, 2014. Amended in 2018.
When I first arrived in Florida with my family in the 1970's, the state's wildlife was something to behold for a family from Pennsylvania. It seemed like everywhere we looked there were exotic animals and plants we had previously only seen in books or on television. My brothers and I were quick to get our our hands on just about anything within reach that crawled, swam, slithered or flew, and lizards were abundant most anywhere you looked outdoors on dry land.
Also known as the Carolina anole, was the one we saw the most of back in those days. As a native species, they're meant to inhabit Florida and other states like the Carolinas. These interesting animals also play important roles in the grand scheme by keeping insect populations in check, and unwittingly offering themselves up as a valuable food source for many larger predators including birds and other reptiles like snakes and north american alligators.
Over time, we saw less and less green anoles in Florida. It wasn't sudden, but like a pot of boiling water, they seemed to slowly disappear. It was while on assignment in Beaufort, North Carolina in 2013, that my brother, Brooks and I were reunited with the species. We almost immediatly talked about how how it's actually pretty rare to see a green anole in our adopted home state of Florida, nowadays.
More recently, while observing a reptilian mating ritual just outside a front window at my home back in the Sunshine State, I recalled that conversation in North Carolina. This common display of rough sex in the wild also reminded me of a precarious balancing act playing out, and how turf wars between even the smallest of animals are signs of a much larger conflict taking place all around the wild kingdom.
I don't do my own dental work either, so when it comes to lizards, I dialed up friend and wildlife expert, George Cera, to get his experience and take on a notable population shift in lizard species. He confirmed that greens are indeed native to Florida, while browns are native to Cuba and the Bahamas, meaning they are classified as exotics or non-natives in Florida. Like me, George also remembers a more abundant population of greens here in Florida a few decades ago. We discussed the reasons behind their conspicuous absence today and what that means.
COSTLY AND CONTROVERSIAL ISSUES DESERVE CLARITY
Consider this. 'Nonnative', 'alien' or 'exotic' are terms that can be used interchangeably to describe species that may or may not become 'invasive' or 'naturalized', once introduced to an environment. In any case, they will never be considered 'native'.
If that sounds a little confusing, you're not alone so let's break it down. According to the Florida Fish and Wildlife Conservation Commission (FWC), most nonnatives are introduced or exotic species, meaning they have been brought to Florida by humans. These types of species are also sometimes referrred to as alien. Brown anoles were first observed in the Florida Keys in 1887, arriving in cargo through the major seaports of South Florida during the 1940's. They became firmly established in most large urbanized areas south of Gainesville by 1980. This would confirm my own timeline and observations. As noted previously, my family and I saw the native green anoles all over the place in Florida during the mid to late 1970's. Right about the same time their decline began, and the same period during which browns were firmly established. According to the FWC, over 500 nonnative fish and wildlife species and 1180 nonnative, exotic or alien plant species have been documented in the state ... so far ... that we know of.
Contrary to popular belief in some circles, including more than a few news and media outlets and even some experts sources, nonnative, alien or exotic doesn't always mean the same thing as invasive; a catchy term thrown around too loosely at times. the United States Department of Agriculture (USDA) defines an invsive species this way.
An invasive species is one that is:
1) non-native (or alien) to the ecosystem under consideration and
2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.
Invasive species can be plants, animals, and other organisms (e.g., microbes). Human actions are the primary means of invasive species introductions.
Important related note here. Whether or not a species is intentionally or unintentionally introduced by humans, if it has adapted to, and reproduces successfully in its new environment, it is considered naturalized. Other nonnative species arrived in Florida by natural range expansions. For example, cattle egrets, a bird species, native to Africa and Asia, flew across the Atlantic Ocean and are said to have arrived in Florida in the 1950s. Other species like the coyote and red fox, spread into Florida by natural range expansions from other states and are now considered 'naturalized'. According to the FWC, a naturalized species is a species not native to an area but one that has adapted and established a stable or expanding population and does not require human assistance for survival and reproduction.
As for our lizards, because evidence suggests the naturalized nonnative/alien/exotic brown anole is the main cause behind reduced populations of native green anoles, the brown anole is therefore also classified as an invasive species in Florida. Again this is based on thier established threat to native species and subsequent harm on the environment.
MOTHER NATURE PLAYS REFEREE
It turns out, the adult male browns are not only superior competitors for the same food sources as green anoles, but are also known to eat green anoles eggs and the species' vulnerable young. Over time, the more aggressive and dominating brown anole species has displaced green anoles through a natural version of eminent domain. To survive this exile, green anoles were forced to adapt from their primary ground territory to an elevated existence in the branches of bushes and trees. This dramatic reduction in their native range and disruption to their routine sustainability caused notable drops in their population causing the powers of natural selection and its key mechanism of evolution to kick in. As a result, green anoles adapted their hunting methods and diet to shift from slower moving ground dwellers like beetles and roaches to more agile flying insects.
Even more compelling are documented physical changes to the anatomy of green anoles that took place during the time since their forced habitat change in Florida. In a study conducted by Yoel Stuart, a postdoctoral biologist at the University of Texas says their feet are now bigger and stickier. In 2014, published findings by Stuart and a handful of other researchers state this evolution took place in just 20 generations of the lizard or about 15 human years. The study states that for greens forced to live in trees and bushes, the toe pad on their longest or fourth toe is larger than greens in areas where the species can still inhabit the ground. The study shows this toe pad also exhibits more scales and thousands of microscopic hairs that enable it to better cling to surfaces; a feature that makes climbing more efficient for this evolved green anole.
A nonnative species that becomes established in a new environment creates a scenario where it could become invasive. If not, for the most part, it's no harm - no foul. However, when a destructive nonnative becomes naturalized and gains enough firm footing, it can be devastating environmentally, culturally and economically. The Cuban tree frog is one example of a species introduced in 1931 through cargo packing materials. It rapidly spread to Florida's natural habitats by the 1970's and is an effective predator of native tree frogs. Burmese pythons became invasive headliners after their prolific expansion into the Everglades where this highly efficient and resilient predator has wreaked havoc on numerous native species populations. Birds and other reptiles including turtles, alligators and their eggs have become a part of the python's diet; an imbalance completely unintended by Mother Nature in this part of the world.
A few thoughts to close. This is not an anti-brown anole or otherwise derogatory wild species message. Instead, it's a cautionary tale about nature's ongoing high wire act where in one instance a curious upside twist of Darwinian fate is displayed for the seemingly insignificant green anole. In another we're baring witness to just how vulnerable the Florida Everglades can be. One thing is certain, in almost every case of destructive invasive wildlife, the cause is either human error, carelessness or just the unintended consequence of man's travels from hither and yon. The full scope and effect of this problem may not be realized for many years to come. More chilling, though, in some cases, a ruinous fallout may ultimately be unavoidable. The fact is some animals simply have no business being here so it is imperative we continue with campaigns to eradicate or at least control those species' advance while avoiding further intrusion from others in the future. For now, out of respect for the bigger picture, consider the following, according the the U.S. Fish and Wildlife Service.
That, my friends, was millions...with a B. The cost is ongoing, astronomical and paid, in part, by the taxable citizenry for often failed attempts at even trying to control the constantly spreading problem. Just a little something to keep in mind the next time you're outside in Florida and see a brown, or if you're lucky, a green anole. Let 'em be, but realize there's an important and pricey turf war taking place all around us.
Thanks for reading. -sp-
Footnote: This extremely broad and highly controversial topic of invasive species has intrigued me since I can remember. I'll definitely be diving deeper into it here and welcome your own thoughts on this subject. Feel free to leave a comment below or let me know, personally.