Monitor lizards eat wildlife, scare people

The African predators are big, fast, smart and aggressive; experts fear their impact on waterfowl.

by Wes Smith, Sentinel Staff Writer, September 12, 2005

SANIBEL -- Wildlife biologist Kendra Willett searched the teeming waters of Tarpon Bay by boat, catching quick glimpses of a stingray, a manatee, a diving osprey and a leaping dolphin.

But it was the creature she couldn't find that worried Willett and other officials and residents on this posh island retreat with a 6,400-acre national wildlife refuge.

The Nile monitor lizard, a cunning carnivore of voracious appetite that has already put fear in the hearts of many in nearby Cape Coral, has made its way across San Carlos Bay to Sanibel, a 17-square-mile island on Florida's southwestern coast.

"We have more than 1,300 waterfowl nests on some of our satellite island rookeries, and we already have reports of Nile monitor lizards on Pine Island and Sanibel," Willett said as she looked for signs of the invader last month. "If these big lizards establish a breeding population and discover the rookeries as a food source, the birds may abandon them."

This is not a gecko-sized problem. And herons, terns and cormorants aren't the only species endangered. Nile monitor lizards are large, nonnative predators capable of wreaking havoc on indigenous wildlife -- and people, too.

"I got a shovel and chased one that hissed at me in my yard. When it ran past the neighbor's house, it saw his reflection in a window and lunged into it so hard I thought it would break," said Steve Sebesta of Cape Coral, where nearly 1,000 Nile monitor lizards are thought to be prowling despite a 2-year-old eradication program.

After reported sightings of the lizards on Pine Island, which lies between Cape Coral and Sanibel, wildlife experts went on the alert. And when a Sanibel resident photographed a Nile monitor in her backyard, city officials put out a warning to the island's more than 6,000 residents.

Sanibel police Chief Bill Tomlinson said traps were being set in the area where the Nile monitor was photographed.

A news release issued by Sanibel City Manager Judie Zimomra warned residents that the lizards pose "an imminent threat."

"Removal of this dangerous exotic lizard is a priority to the sustainability of our island's environmental health, and we are treating it as such," Zimomra said.

At risk are the island's snails, clams, crabs, fish, amphibians, reptiles, birds and mammals, including domestic pets. They also might pose a threat to human babies, the city manager said.

The presence of the menacing monitors is particularly sensitive on Sanibel. The island has had a series of alligator attacks on humans in recent years. Officials killed eight large gators and put a more aggressive removal program in place after two local residents died and two others were injured. A state study of the island's alligator population is expected to begin in October.

The Nile lizards are not as bulky as alligators but can grow to lengths of 7 feet. Though they will normally flee humans, they can become aggressive when cornered. Cape Coral residents have encountered Nile monitors raised up on their rear legs, slashing out with their curved claws and whipping at them with powerful tails.

This lizard's arsenal also includes a powerful bite and a pungent "squiddy smell" they emit when threatened, according to biologists.

"I used to like calamari, but now just a whiff of it gives me flashbacks to hiding in the bush tracking these lizards," said Harry Phillips, an environmental technician who has helped trap 110 lizards in Cape Coral.

Phillips said that the local Nile monitors also have exhibited disturbing Jurassic Park-raptor hunting techniques.

"They've been known to work together to distract a bird while one goes up and gets the eggs out of the nest," he said.

These long-necked, forked-tongue natives of Africa's Nile River basin have been imported and bred as exotic pets in the United States.

Biologists speculate that pet traders or owners in the Cape Coral area released breeding pairs in the city's southwestern neighborhoods where hundreds of miles of canals, vacant lots and mangrove swamps have provided them a haven.

"They don't have any natural enemies here unless we import some Nile crocodiles to prey on them. But they have been known to eat each other," Phillips said.

The Nile monitor lizards pose a considerable threat to Cape Coral's prized population of burrowing owls. Some suspect that they are also responsible for a sharp decline in the number of stray cats in the area.

Two years ago, officials in Cape Coral launched an eradication program to eliminate the lizards that "will eat anything that moves or smells good -- or even that smells bad," according to Todd Campbell, a University of Tampa biologist who has led the city's campaign.

Campbell said his worst fear has been that the lizards, which can stay submerged for an hour or more, would migrate from Cape Coral's residential areas to Sanibel's J.N. "Ding" Darling National Wildlife Refuge, which encompasses forests, marshes, and coastal islands within Pine Island Sound.

"I am not being an alarmist but these things get really large," Campbell said. "They are really intelligent. They can find bird rookeries. And they can remember from year to year where to go back."

The eggs of gopher tortoises, another prized Snail native species, also would be threatened by the Nile lizards, which eat the eggs and take over the burrows. The lizards reproduce at a high rate, laying as many as 84 eggs at a time. They are also highly mobile. They can swim long distances and are fleet of foot, having been clocked as fast as 18 mph.

"I encountered a 5-footer on a refuge on the East Coast, and it was literally leaving us in the dust as it ran down a levee," said Bill Thomas Jr., head of the Invasive Species Strike Team for the U.S. Fish and Wildlife Service, who is based on Snail Island.

"One of my workers ran as fast as he could after it, and he was not making up any ground. It was like a top-fuel dragster against a stock muscle car," Thomas said.

Note to birds, squirrels and tree frogs: Nile monitor lizards can climb, too.

"People have seen them on their roofs and up in trees. The top of a house is just a weird-looking cliff to them," said Phillips, who captured a 4-foot Nile monitor in a baited cage recently only to have a resident tell him that it wasn't "the big one" that has been roaming the neighborhood.

Cape Coral's Nile-monitor-lizard extermination program went through its $47,000 in grant funding in its first two years, but new funding is being sought. More than 350 complaints and sightings have come in so far, said Kraig Hankins, an environmental biologist with the public-works department.

Some residents have joined the hunt. A veteran alligator trapper lassoed a 6-foot-long Nile monitor lizard with an electric cord and tied it to his dock before calling Hankins one day, he said.

"But my favorite was this lady who shot and killed a footlong monitor lizard with the BB gun she'd just gotten her son for Christmas last year," the biologist recalled. "She wanted me to come and pick it up before her son got home. It seems she'd told him that people should never shoot what they weren't going to eat."

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