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Professor at University of Tampa speaks about invaders from another part of the planet

Todd Campbell studies invasive reptiles and amphibians that have settled in Florida
Herpetologist Todd Campbell said more than 50 invasive species of reptiles and amphibians live in Florida.
Herpetologist Todd Campbell said more than 50 invasive species of reptiles and amphibians live in Florida. [ Photo: Courtesy Todd Campbell ]
Published Oct. 30

Times Correspondent

The Nile monitor lizard, a seven-foot-long creature with sharp teeth, has settled comfortably in two areas of Florida, says herpetologist Todd Campbell, a University of Tampa associate professor who led the effort in the early 2000s to study, trap and remove the predators that had taken over Cape Coral.

They join the Argentine black and white tegu lizard, a five-foot long animal that devours fruits, vegetables, bird and turtle eggs. It’s found in thriving populations in South Florida and Hillsborough County. And the plant-eating iguanas, so plentiful in Broward and Dade counties that you see them in the grass next to busy intersections.

Campbell, 60, researches invasive reptiles and amphibians. He talked with the Tampa Bay Times about the intruders.

Are monitor lizards still roaming Cape Coral?

Oh, absolutely. There are three separate populations of what’s called the Nile monitor lizard in Florida that we know of. There might be more. But right now the Cape Coral population is the largest and probably the oldest, resulting from some releases, we’re estimating, back probably in the late ‘80s. In the ‘90s they started expanding to the point where in… the early 2000s people started noticing them enough to complain about them to the city of Cape Coral.

Now there’s another population also in West Palm Beach along the C-51 canal. ... So that’s a different population that is absolutely established there. I would call it at least stable if not expanding.

There’s another population that I was notified about… over 10 years ago in the Homestead area, right in basically southern Homestead. I contacted the fish and wildlife and National Park Service people – actually they contacted me – and I went down there and trained them how to find burrows, how to trap them and all that. ... I think they caught something like 20 or more animals. I haven’t heard anything since so I think it’s possible that they got rid of that population. If not, they knocked it down pretty hard and it’s still fairly small.

OT_307704_PEND_Lizards (06/15/2009Cape Coral, FL) Todd Campbell, an Associate Professor of Biology at the University of Tampa, removes a Nile Monitor from a trap at the Cape Coral home of Robert Dudley Monday June 15, 2009.
OT_307704_PEND_Lizards (06/15/2009Cape Coral, FL) Todd Campbell, an Associate Professor of Biology at the University of Tampa, removes a Nile Monitor from a trap at the Cape Coral home of Robert Dudley Monday June 15, 2009. [ PENDYGRAFT | St. Petersburg Times ]

What do they eat?

They eat whatever they want to eat. All those questions about do they eat dogs and cats, I’m certain that they do. Whether or not that’s a prevalent thing is another aspect, but we’ve got what looks like cat hair in at least a couple of stomachs. They certainly could easily gobble up a litter of kittens with no problem. And a large male monitor could probably take down an adult cat or a small dog.

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How many different species of invasive reptiles and amphibians are there in Florida?

From my last knowledge, there are over 50 species of reptiles and there’s at least three species of non-native amphibians established in Florida, possibly four. … Almost all of the reptiles are lizards. We’ve only got a few snakes. As you know, we’ve got the pythons (in the Everglades) ... we’ve got a couple of species of pythons and the boa established in at least one place down in Miami. But for the most part there’s about 50 species of lizards… There’s more non-native species of lizards in South Florida than there are native lizards in the United States.

What are they doing to native populations?

We know a lot about… the brown anole, which is from the Bahamas and Cuba. ... We know a lot about this one because of my work on the interaction between the brown anole and the (native) green anole. I demonstrated in my dissertation a long time ago that brown anoles will cause green anole populations to decline by something like 80 percent… within a couple of years after their introduction. ...

Once the brown anoles come in, the green anoles move up in the trees… and they are forced to eat lesser quality and quantity of prey items that are harder to catch. …

But the more important thing is brown anoles eat green anoles’ hatchlings. Green anoles also eat brown anole hatchlings, but brown anoles are naturally much more abundant, probably 10 times more abundant in the environment. So what that means is green anole hatchlings have to run a gauntlet of brown anole adults. They’re just sitting there waiting for them.

Professor Todd Campbell an expert on the tegu and Nile monitor lizards, holds the frozen remains of a Nile monitor lizard.
Professor Todd Campbell an expert on the tegu and Nile monitor lizards, holds the frozen remains of a Nile monitor lizard. [ PHILIP MORGAN | Philip Morgan ]

The Argentine black and white tegu lizard is in Hillsborough County. Where else is it?

As far as I know … there are only two established populations of the Argentine black and white tegu. Just like the monitor, while you may find individuals... in other places, the established populations I think are only in Homestead and Florida City and along the canals in the Everglades and in southeastern Hillsborough county in some rural areas.

What do they do to the environment?

They are another large lizard. … The other thing about them is they are more omnivorous. The monitors are pure predators, 100 percent. … The tegus, they are truly omnivorous, they eat a lot of fruits and vegetables. … When we open their stomachs, they have a lot of palm fruits in their stomach, along with things like insects and other vertebrates and stuff. But one thing that they do eat which makes them easy to catch is they eat a lot of bird eggs. So when we trap them we exclusively use… chicken eggs.

Iguanas seem to have taken over South Florida.

People loved them, like, 20, 30 years ago. People absolutely loved them; They loved having them around. And I said it many years ago: Well, when they start becoming really abundant and they eat all of your flowers and all of your landscaping, you’re not going to feel the same way about them. ...

Because they’re a very tropical species, unlike the monitors and the tegus… when we get a cold snap, the next day you’ll have all kinds of news articles about iguanas falling out of the trees. Because they’re very, very sensitive to cold. So the populations keep getting knocked back during cold years, and then between cold years the populations just rebound.

How do you destroy invasive species?

If it’s a larger animal, it’s much better to take it to a veterinarian to get it properly euthanized in an ethical manner.

You say if it’s a small invasive animal, like a cane toad – whose poison is deadly to dogs – the general public can destroy it by putting it in the freezer.

You can also use Benzocaine. You can rub Benzocaine on a frog or a toad and that’s actually an accepted method for euthanizing amphibians, because they absorb it in their skin, and they will just go to sleep.