Florida's Invasive Species -- Nile Monitor Lizard
Another nightmare that moved to Florida.
When I was just beginning to think about what I wanted to write about next a friend came to my rescue. She had recently seen a news report about a Nile monitor lizard sighting in Cape Coral. I had a vague recollection of hearing about Nile monitor lizards but really didn’t know much about them. So here’s what I found out.
The Nile monitor grows to over 6 ft long and has strong jaws and sharp claws. Originally from West Africa where they’re a top predator they’ve even been known to prey on crocodile nests and young crocs. They’re strong swimmers and can run quite fast for short distances. They climb trees to find bird nests and eat fruit.
The Nile monitor also has a very wide range of food in its West African habitat:
Nile monitors feed on a wide variety of prey items, including fish, frogs, toads (even poisonous ones), small reptiles (such as turtles, snakes, lizards, and young crocodiles), birds, rodents, other small mammals (up to domestic cats and young antelopes [Raphicerus]), eggs (including those of crocodiles, agamids, other monitor lizards, and birds), invertebrates (such as beetles, termites, orthopterans (grasshoppers), crabs, caterpillars, spiders, millipedes, earthworms, snails, and slugs), carrion, human wastes, and feces.
So, how did such an awful pest get to Florida? Most likely in the exotic pet trade. Some people really like to have unusual pets. However the problem with many exotic pets come as they grow. They can get really hard to take care of. Or as Daniel Bennett, author of a book on monitor lizards says:
There are few lizards less suited to life in captivity than the Nile monitor. Buffrenil (1992) considered that, when fighting for its life, a Nile monitor was a more dangerous adversary than a crocodile of a similar size. Their care presents particular problems on account of the lizards' enormous size and lively dispositions. Very few of the people who buy brightly-colored baby Nile monitors can be aware that, within a couple of years, their purchase will have turned into an enormous, ferocious carnivore, quite capable of breaking the family cat's neck with a single snap and swallowing it whole.
So, yeah, pet Nile monitor lizards are a really bad idea. They’re illegal to keep as pets in Florida except for some permit owners that were grandfathered in when the ban was passed. But pet owners love their pets and most don’t have the heart to kill a pet they’ve been feeding and watching grow for a couple of years, no matter how vicious. Oftentimes the pet is taken to a wild area and released. Releasing tropical and subtropical pets in the north isn’t much of a problem. They wander around until winter then can’t survive the cold. In Florida they not only survive but may find others of their kind to start a breeding colony. That’s probably what happened with the Nile monitor.
So where are the monitor lizards? Well, not where I would have expected. I thought that the center of population would be in Miami-Dade, like a lot of other tropical invasive species. But I was surprised at the distribution. Here’s a chart from EDDMapS of Nile Monitor sightings by a group from the University of Georgia that creates tools to track sightings of invasive species:
There are some in Miami-Dade, but not as many as I would have thought. The epicenter of the Nile monitor invasion is the Coral Gables area with a smaller grouping in Broward County. What do these places have in common? They’re far enough south that the lizards can survive the cold winters but these places have lots of open water. This gives these semi-aquatic lizards a way to travel throughout the area and access a diversity of prey.
However the Florida Fish and Wildlife Commission sees the real risk is they will inhabit Central Florida. The lakes and rivers of central Florida will make them hard to control.
So what’s to be done about the pests? The options are limited. My first thought is that a bounty program where hunters are paid to kill Nile Monitors. But I’m not sure that would work well. These critters are too dangerous for untrained hunters to take on without the use of firearms. That may be tough since much of their range is in or near populated areas. Bounty hunters looking for iguanas in the Florida Keys use air rifles to stun or kill the smaller lizards. But I doubt that would work with Nile monitors.
But the only way to halt their movement may be by employing professional trappers to at least slow their spread. Coral Gables is doing this now to mixed results.
In the end the only thing they can do may be to slow the spread. Maybe in the intervening decades something will change to help with control — a disease, or maybe a new technology. That’s what it will take to keep Nile monitors out of Central Florida.