Invasive Reptiles Are Taking Over Florida—and Devouring Its Birds Along the Way

GCC Faculty Insights:

“I think this article nicely underscores the tension between the right of people to own non-regulated animals and the reality that many cannot handle them. They believe they are doing the humane thing by releasing them into the wild, only to accidentally initiate an invasion. Fairly common story actually. Demonstrates the need for both better education of the public (and pet trade in particular) and tighter regulation of trade animals.”

Jacob Barney, Associate Professor of Invasive Plant Ecology in the School of Plant and Environmental Sciences

Birds like Roseate Spoonbills and Burrowing Owls are ending up in the stomachs of hungry pythons and nile monitors. Is it too late to stop them?

t’s a sweaty morning last June on the outskirts of Tampa, and droves of reptile enthusiasts are streaming into an air-conditioned expo center. Some have woken early to trek out to the Florida State Fairgrounds to get first crack at the animals of Repticon, a weekend-long extravaganza that’s similar to a baseball card convention, except instead of mint-condition Mickey Mantles and Pete Roses there are green anacondas and meat-eating lizards. One vendor’s table is covered in flimsy plastic catering trays that are filled with ball pythons. Others are selling Asian water monitors, gargoyle geckos, yellow rat snakes, and bearded dragons. A guy strolls by wearing a “Snakes Lives Matter” t-shirt. Another man, who has a three-foot-long lizard slung across his chest like a bandolier, is at a nearby booth admiring a young boa constrictor that’s twirling around his girlfriend’s fingers. Price? $100. Sold.

Roughly 60 Repticons take place each year, from Phoenix to Oklahoma City to Baltimore, attracting an estimated 200,000 visitors. These shows represent but a tiny sliver of the live-reptile trade, a loosely regulated industry that spans the globe and generates an estimated $1.2 billion in revenue annually, according to the United States Association of Reptile Keepers. In much of the continental United States, these cold-blooded creatures aren’t likely to fare well outdoors should they escape or be set free. But the sub-tropics of South Florida are different, and the best adapted have not only survived in the wild, they have thrived. To date the Florida Fish and Wildlife Conservation Commission, or FWC, has identified 50 types of non-native lizards, turtles, crocodilians, and snakes within state limits, more than anywhere else in the world.

For the birds of Florida, this blitz of exotic predators poses an existential-scale threat. The Burmese pythons, which stalk wading birds in the Everglades, have become so menacing that the state has hosted derby-style competitions to catch them. Farther north, Nile monitors—the largest lizard in Africa—have been terrorizing a population of Burrowing Owls in the city of Cape Coral. And on the outskirts of Florida City, just outside Everglades National Park, egg-eating Argentine tegus could soon raid the nesting grounds of one of the last remaining populations of the endangered Cape Sable Seaside Sparrow. Each of these reptiles found their way to Florida via the pet trade—but while most people acknowledge that’s a leaky pipeline, few agree on whether and how to plug it.

Take Ed Poelsma, who’s wandering Repticon with Pugsly, a five-and-a-half-foot-long black-throated monitor that’s a close relative of the Komodo dragon. Pugsly is a stunning creature that looks to be from prehistoric times, with claws like steak knives, camouflaged skin, and a muscular tail. What does Pugsly eat? “Meat,” Poelsma says. “He would eat anything you put in his cage that’s meat. Literally anything.” No, Pugsly has never bitten Poelsma, and yes, he considers the giant lizard to be part of his family. He takes Pugsly for walks in his neighborhood, maintains an Instagram page for the animal, and happily answers questions from curious onlookers. You don’t need a permit to buy a Pugsly of your own, and that’s how Poelsma thinks it should be. “If you want to look at invasive animals in the wild, the very worst thing in the world is a domestic cat,” he tells me. “Go to the local ASPCA or local pound and look at all the dogs and cats . . . But everybody wants to blame the reptile owners for being an irresponsible pet owner.”

Five-year-old Drew Belliston walks “Rock,” an Argentine black and white tegu, in his backyard. A Florida trapper caught Rock as a yearling in the wild and sold it at a reptile expo. Drew’s father Devin, who owns several other lizards and reptiles, acquired Rock when the original owner could no longer keep it. Photo: Karine Aigner

It’s a sentiment that almost everyone I meet at Repticon echoes, including Greg Graziani, who has starred on National Geographic’s The Python Hunters and now runs a reptile-breeding facility and serves as an amnesty point for FWC. If someone wants to get rid of a reptile they shouldn’t have or can no longer control, Graziani can arrange a no-questions-asked drop off. Of course invasive reptiles are a problem, he says, but so are invasive plants, trees, and mammals. And as for the risks Argentine tegus, Burmese pythons, and Nile monitors pose to the menagerie of birds that depend on Florida’s lush landscapes, Graziani is empathetic but unconvinced. “The bird people are worried,” he says. “I understand their concern. But I haven’t seen the science.”

Truth is, scientists have never seen anything quite like this.

It’s the Monday morning after Repticon and I’m in a vacant lot in Cape Coral watching Bob Mondgock smack a package of frozen chicken with the claw end of a hammer. He pries free a hunk of raw poultry and tosses it to the back of a spring-plated trap in hopes of luring in one of the invasive Nile monitors that haunt this Gulf Coast city.

Over the years Mondgock has tangled with more monitors than he can remember. He works for the Cape Coral Environmental Resources Division, a six-person unit that might very well have been the inspiration for Parks and Recreation. Mondgock is the Ron Swanson of the group: a mustachioed Libertarian who will under no circumstances let me turn on my tape recorder. Before getting back into the truck, he clips an armful of fronds from a nearby bush and piles it around the trap. It’s less about camouflage than it is about making sure there’s enough shade to keep curious cats and raccoons from baking to death if they get stuck.

A graduate student and biological technician at the University of Florida baits a tegu trap with an egg and a potato. The egg is the tegu bait and the potato serves as a source of hydration to prevent death if a mammal gets trapped instead. The traps are checked daily. Photo: Karine Aigner

Nile monitors have no business in this hemisphere. As their name implies, they should be basking along the shores of Africa’s Nile Delta, but they got popular in the pet trade and rumor has it that the owner of a now defunct pet store, scheming a source of free inventory, let some loose behind his shop so they would breed in the wild. Unsurprisingly, the lizards quickly fanned out across Cape Coral’s extensive canal system. The first sighting likely dates back to before 1990, though it wasn’t until the early 2000s that they began regularly popping up in people’s backyards. If you’re not accustomed to large lizards, an adult Nile monitor dashing across your lawn might be terrifying. They can top seven feet, swim like Michael Phelps, and eat rodents, birds, rabbits, wasp nests, venomous rattlesnakes, poisonous cane toads, and, according to some residents, cats and dogs.

There’s no telling how many Nile monitors are out here. Since 2000, the city has logged more than 2,500 sightings and trapped 564 of the animals. Over all those years, though, no one has uncovered a monitor nest, an unsettling tidbit given that the lizards can lay up to 60 eggs at a time. Conservative estimates put their population at 1,000, a lowball number in Mondgock’s eyes. The city usually sets traps in response to residents calling in sightings, he explains, and many residents are so accustomed to the animals that they don’t bother calling one in. Today Mondgock will bait 11 traps, all within view of nice homes with pools, screened-in porches, and garages.

As we drive from site to site, we pass a handful of dusty lots where Burrowing Owls perch on wooden stakes and look like adorable stuffed animals. That the city is home to one of the world’s largest populations of Burrowing Owls is a point of pride among some residents, not to mention a good tourism draw. The owls are staring down a long list of threats, including significant habitat loss, and FWC declared them a threatened species in November 2016.

It’s known that Nile monitors eat Burrowing Owls—after all, the lizards are expert burrowers and ground hunters. What’s unknown is the number of owls they have devoured. One of the first confirmed cases dates to May 2005, when a woman saw a large monitor in her yard with one of the tiny tawny owls clenched in its jaws. Unfazed, she grabbed a flowerpot and threw it at the lizard. It dropped the owl and bolted away, but the bird did not survive. At least two other instances of monitors eating owls have been reported, and it seems certain that other attacks have gone unseen and undocumented.

Owls aren’t the only birds in monitors’ crosshairs. The lizards hunt cooperatively and are known to team up to lure birds off their nests so they can pillage the eggs, according to a report by Todd Campbell, a biologist at the University of Tampa and a leading expert on Nile monitors. “Many of Florida’s wading birds would be an easy target while foraging in mangroves and along tidal creeks and artificial canals,” the 2008 report warns, “and Nile monitors are excellent tree-climbers, so the nests of wading birds are also at risk.”

Cape Coral is home to one of the largest populations of Burrowing Owls. Nile monitors, invasive lizards that also abound in the area, are known to eat the birds—but just how often is still a mystery. Photo: Karine Aigner

 

Back at Repticon, I saw at least five different types of monitors for sale. It’s a family of lizards that has roughly 70 species and only two—the Komodo dragon and the Nile monitor—are now tightly regulated here. FWC classifies the Nile monitor as a Conditional Species, along with only seven other reptiles, including the Burmese python and reticulated python (at nearly 30 feet, one of the largest snakes in the world). These species can’t be sold as pets, but with the right permits you can have them for commercial, research, and exhibition purposes. Dozens of other monitor species—crocodile monitors, Argus monitors, tree monitors—can be brought and sold no problem.

It’s a situation that draws criticism from both sides. Those who would like to see more control over the reptile trade consider it a gaping regulatory hole that could allow new invasive species to flourish. Those in the pet trade see it as evidence of how arbitrary and inconsistent the rules are. When I met Ed Poelsma and Pugsly at Repticon we were standing a few feet away from a female Asian water monitor that had a $1,000 price tag. Under the right conditions, it could grow up to 8 feet long, weigh 100 pounds, live for 15 years, and is every bit as capable of surviving in a South Florida suburb as a Nile monitor. The two animals have similar diets, reproductive habits, and hunting tactics. “A Nile monitor is basically the African version of an Asian water monitor,” Poelsma told me, pointing at the one for sale. Yet one is regulated and one is not.

Mondgock, the city employee, isn’t keen on discussing whether or how the pet trade should be controlled other than saying that Nile monitors “ARE. NOT. PETS.” He’s been bitten, scratched, peed on, and pooped on enough times (he was chasing them, not the other way around, he says) to know that these animals never play nice.

Two days after we part ways, one of the 11 traps we set nabs a three-foot Nile monitor that was first spotted climbing a resident’s front door. Like nearly all the monitors Mondgock traps, it was placed into a sealed plastic tube and exposed to a lethal dose of chloroform. Death by asphyxiation—a grisly fate, but what other options are there?

Biological invasions aren’t necessarily blitzkriegs. It doesn’t matter if a pet store releases a few dozen lizards or a hurricane damages a breeding facility and sets free hundreds of snakes, as has happened. Some of the invaders die off, scooped up by predators or unable to adjust to their new environs. Others find food, find a mate, and survive. It’s in those early days of their arrival, before generations of the species are hatched, that there’s a chance at eradication. But with each new egg that’s fertilized and each animal that reaches sexual maturity, the monetary and ecological costs of the problem goes up. Biologists call this the invasion curve, and right now Nile monitors fall somewhere in the middle. Any hope of eradication in Florida faded long ago, but it may be possible to keep them contained to a few small pockets around the state—one is in Cape Coral, another is in Palm Beach County, where President Trump’s Mar-a-Lago resort is located.

Containing the booming Burmese python population has become virtually impossible for the Florida Fish and Wildlife Conservation Commission, and so the agency and its partners created the month-long Python Challenge to enlist the help of the public. Pythons are believed to have decimated the Everglades’ populations of small mammals, but they will also eat waterbirds like herons, egrets, ibises, and spoonbills. Photo: Karine Aigner

Keep following the invasion curve upward, past the point of containment, past the Nile monitor, all the way to the top, and you will find the Burmese python. This apex predator can grow more than 18 feet long and was for a long time one of the most popular snakes in the pet trade. Now, there are estimated tens or hundreds of thousands of Burmese pythons in South Florida and they’re eating everything—rabbits, rats, bobcats, deer, even alligators. On the invasion curve, they fall in the “resource protection and long-term management” section. In other words, they’re taking over, and our only hope is to safeguard what they have not yet destroyed.

“Pythons are definitely eating birds,” says Brian Smith, a biologist who works for Cherokee Nation Technologies, a company contracted by the United States Geological Survey to help manage the invasive Burmese python population. A few years ago, Smith went to capture a python in Everglades National Park. The snake was in a shallow marsh and Smith noticed a bulge in its stomach. He moved in and grabbed the python near the base of its head. Suddenly two bird feet popped out of the snake’s mouth. A moment later, another two feet shot out. The snake writhed and in one fell swoop regurgitated a pair of full-grown Great Blue Herons. Smith couldn’t believe his eyes as the corpses poured out and flopped to the ground. Both birds’ heads were missing; other than that the animals were intact and easy to identify.

Smith’s gruesome anecdote raises an important question: Could Burmese pythons devour resident birds of the Everglades the same way they did the small mammals? In 2012, a team of researchers reported in the Proceedings of the National Academy of Sciences that marsh rabbits, raccoons, and opossums had all but vanished from sight in Everglades National Park. One of the culprits, they suggested, was the arrival of the Burmese python, which records show was established in the park around 2000. If that’s the case, it took the snakes just a decade to eat their way through that section of the ecological menu. Knowing whether they have completely shifted their diet to wading birds for their next course is difficult to determine, though.

Christina Romagosa is a wildlife ecologist at the University of Florida, where she specializes in biological invasions. After a Burmese python is captured, it is euthanized and necropsied by biologists who remove the gut contents, freeze them, and then send them to Romagosa’s lab to decipher. Photo: Karine Aigner

“I think that it is possible,” says Christina Romagosa, an assistant research professor at the University of Florida, “but I am having a hard time showing it because we really don’t know what’s out there for them to eat.” Some evidence sits on Romagosa’s desk: several plastic bags containing the remains of a Roseate Spoonbill. One is filled with bones; another has the bird’s feet. The biggest bag holds dozens of soft pink feathers, some still in sheath. A few days earlier, the remains of the spoonbill were found in the gut of a Burmese python that had been run over by a motorist. “It looks like maybe this bird was molting,” Romagosa speculates.

It is anyone’s guess as to what one heap of python poop might reveal. There can be tufts of mammal fur, fragments of bird feathers, crushed bones, disembodied beaks, and occasionally flecks of eggshell, and accurately identifying what species trace evidence originated from is tedious. Sometimes the bird parts are so degraded that Romagosa cannot identify the species, so she ships them off to Carla Dove, head of the Smithsonian Institution’s Feather Identification Laboratory. Dove is very concerned by the variety of birds eaten by pythons. “It’s crazy,” she tells me. “These birds didn’t evolve with this kind of predator.”

 
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