10/24/2026
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Between 2012 and 2016, Frank Mazzotti’s team at the University of Florida removed 68 Nile monitors from canals and neighborhoods in Palm Beach and Broward counties, opened them up, and catalogued everything inside. Sixty-five of the lizards had food in their gut. The total count was 1,484 individual prey items.
A Nile monitor is an African lizard that can grow over six feet long and weigh more than 20 pounds. It is semiaquatic, fast, and aggressive. It arrived in Florida through the pet trade, probably through both intentional and accidental releases, started breeding in the wild by the 1990s, and is now established in at least three counties. Florida banned possession in 2021. Mazzotti called them very active and very wild. “They don’t calm down,” he said. “They don’t make good pets at all.”
The diet breakdown showed an animal that eats everything and specializes in nothing. The 1,484 prey items spanned eleven categories: gastropods, millipedes, crabs, spiders, insects, fish, lots of frogs, snakes, reptile eggs, birds, and mammals. Adults had the broadest diet of any size class. Males and females ate the same things. Among the reptile eggs were whole clutches of green iguana eggs. Among the frogs were cane toads, found in 10 of the 65 stomachs.
Cane toads are lethally toxic to most Florida predators. Their parotoid glands secrete bufotoxin, a cardiac poison that kills dogs, raccoons, bobcats, and native snakes that bite into them. The Florida wildlife management strategy for cane toads is built partly around the fact that native predators cannot safely eat them. Nile monitors ate them whole with no apparent ill effects.
What the Mazzotti study did not cover is what residents across the state have been reporting for two decades. Todd Campbell, a University of Tampa biologist who ran the first eradication effort in Cape Coral for the Charlotte Harbor National Estuary Program, documented those accounts in his 2005 report.
In May of that year, a resident of southwest Cape Coral watched a large Nile monitor walk up and seize a Florida burrowing owl nesting in her yard. She threw a flower pot at the lizard. It dropped the owl and ran. The owl died anyway. Its body went to a state biologist, and it became the first confirmed case of Cape Coral’s monitors killing a protected species.
One man watched a monitor tear apart and eat a marsh rabbit in his backyard. Young monitors emptied two families’ goldfish ponds. A woman who lost two Dachshund puppies while they played in her yard believed a monitor took them, though nobody confirmed it. Feral cats and domestic pets were disappearing at rates residents had not seen before. In 2013, a Nile monitor is believed to have killed a cat in the Cape.
The largest lizard Campbell’s team captured was nearly six and a half feet long and weighed about 27 pounds. He called the species nearly untamable. Over a hundred monitors were caught and euthanized during his study, and Campbell concluded that total eradication from Cape Coral was no longer feasible.
The monitors raid nests. They dig into gopher tortoise burrows, which are protected under state law, and eat the occupants. In Africa, Nile monitors routinely raid crocodile nests, eating both eggs and hatchlings. In Florida, they have been documented doing the same to alligator nests. One was found near Key Largo close to nesting habitat of the endangered American crocodile.
Mazzotti’s team concluded that the combination of broad diet and active foraging behavior meant that food availability was unlikely to limit the spread of Nile monitors in Florida. The lizard eats what is available, switches when something runs out, and tolerates prey that kills its competitors. The Palm Beach population along the C-51 canal has resisted trapping efforts that worked on the same species in Cape Coral. The monitors are too fast, too wary, and too well fed.
Image is for illustration purposes only.
Source: Mazzotti, Nestler, Cole et al. (2020), Journal of Herpetology 54(2): 189-195 / Campbell (2005), Charlotte Harbor National Estuary Program / FWC / USGS
