By Kim Smiley
Florida’s warm climate has made it an appealing home to many invasive species, such as Burmese pythons (see our previous blog) and giant African land snails. Researchers fear another species, the Nile monitor lizard, is also threatening native wildlife. Nile monitor lizards are intimidating reptiles, growing up to 5 feet long, and they are not fussy about what they eat, consuming almost anything smaller than they are. They will feed on mammals, birds, reptiles, amphibians, fish and eggs. There have even been reports of Nile monitor lizards making a meal out of pet cats.
This issue can be analyzed by building a Cause Map, a visual format for performing a root cause analysis. A Cause Map visually lays out the cause-and-effect relationships that contribute to an issue so that they are easily understood. The first step in building a Cause Map is to fill in an Outline to help define the problem. Basic background information is recorded in the Outline in addition to how the problem impacts the overall goals. To build a Cause Map, start at one of the impacted goals, start asking “why” questions and add the answers to the Cause Map. For this example, we will focus on the environmental goal.
Invasive Nile monitor lizards impact the environmental goal because they can have a negative impact on native wildlife. Why? Monitor lizards eat a varied diet and there are permanent breeding populations of these lizards in Florida. Why are there populations of Nile monitor lizards in Florida? They were introduced into the environment and the number of Nile monitor lizards in the wild quickly increased. (It’s a bit awkward to write out the “why” questions in this way, but click on “Download PDF” above to see how the Cause Map would visually lay out for this example.)
Nile monitor lizards are basically a perfect (or perfectly bad, depending on your point of view) invasive species. They grow quickly and breed at an early age. They lay many eggs at once, as many as 60 eggs in a single clutch. Their natural habitat is very similar to southern Florida and they have a tendency to wander over long distances so it isn’t surprising that they would quickly spread from where they were originally introduced into the wild.
Researchers don’t know exactly how Nile monitor lizards were first introduced into the wild, but it typically occurs when pets escape or are released. Nile monitor lizards are sold as pets. Often they are small when sold, but they quickly grow large and can be aggressive. Owners may release their pets into the wild if they become tired of them or are unable to continue caring for the lizards. It’s easy to see how a small pet lizard may seem like a good idea, but turn out to be a less than ideal roommate when they have grown into a large, active predatory adult lizard, complete with sharp claws and teeth. Not to mention, the cost of feeding such a pet might be more than anticipated.
Researchers are still working on developing the best methods to control Nile monitor lizard populations in Florida. (It is unlikely that Nile monitor lizards will ever be eradicated from Florida, but officials hope to control the numbers.) Three permanent breeding populations of Nile monitor lizards have been identified, one of which is estimated to be hold over 1,000 lizards.
DNA testing has shown that there are actually two distinct species of Nile monitor lizards and all lizards tested in Florida have been determined to be the newly-named West African Nile monitor lizards. West African Nile monitor lizards aren’t likely to spread too far north in Florida and beyond because they aren’t adapted to cold weather. The other species of Nile monitor lizards is native to a cooler part of Africa and could potentially spread to a wider area if ever introduced into the wild in the United States.
Bottom line: please don’t release any nonnative species anywhere (even goldfish – see our previous blog). You may think you are doing the right thing for your pet, but invasive species can do massive damage to native wildlife. Call a pet store or your local fish and wildlife service if you can no longer care for a pet. You can also help by reporting sightings of nonnative species to your local fish and wildlife services.