The Nile monitor (Varanus niloticus) is a semi-aquatic lizard that is not native to Florida. Nile monitors are olive green to black in color and have cream-colored or yellow stripes on the jaw and head. They have rows of yellowish, V-shaped stripes beginning at the base of the skull and neck which transform into bands or spots along the back. Their lightly banded tails are usually 1.5 times the length of their bodies and are shaped like a rudder to aid in swimming.
Nile monitors may be observed basking on rocks and branches and are often seen in or close to water. They are mostly active during the day. At night they may sleep on branches or submerged in water in warm weather or retreat to burrows in cooler weather. Nile monitors are skillful climbers and adept swimmers. They can remain under water for 12-15 minutes.
Female Nile monitors reach sexual maturity at about 2 years or when they attain lengths of about 14 inches. Eggs are typically deposited into burrows, and clutches consist of 12-60 eggs depending on the size of the female, with larger females laying more eggs. Males will mate with many different females and engage in fierce wrestling competitions with other males for mating opportunities. Nile monitors can live up to 20 years in captivity. They are the largest lizard species in Africa and can attain lengths of about 6.5 feet and weigh up to 17.8 pounds, although a typical adult averages 5 feet in length and weighs close to 15 pounds.
Nile monitors are generalist feeders and hunt for prey on the surface, below ground, in trees and in fresh and saltwater (Losos and Greene 1988). Their broad diet includes crabs, crayfish, mussels, snails, slugs, termites, caterpillars, beetles, spiders, grasshoppers and crickets, fish, frogs, toads, lizards, turtles, snakes, young crocodiles, and other reptiles, birds and their eggs, and small mammals.
Aside from desert regions, the Nile monitor occurs throughout the Nile River delta in sub-Saharan Africa. Thirty-three countries from Senegal to Somalia and from Egypt (Nile Valley) to South Africa also report observations of this lizard. Nile monitors may exist at altitudes as high as 6,560 feet above sea level.
Nile monitors have known breeding populations in Lee, Miami-Dade, and Palm Beach Counties, although observations have occurred throughout the state including multiple observations in Broward County. South Florida’s extensive canal system may provide dispersal corridors for the species, which tends to inhabit water edges. Researchers believe populations of Nile monitors in Florida stem from intentional and unintentional releases from animals in captivity. Nile monitors may escape confinement by pushing off the tops of cages or by using their sharp claws to tear through screens. They may be intentionally released if they become difficult to feed, manage or handle or if they are deemed unfit or too sick to sell in the reptile trading industry. Nile monitors may also escape from facilities destroyed by hurricanes.
Due to their generalist diet, Nile monitors may impact state- and federally-listed species including sea turtles, wading birds, gopher tortoises and the American crocodile. The largest population of burrowing owls in Florida occurs in Cape Coral, where the largest known Nile monitor population also occurs. The Nile monitor’s high reproduction rate, diverse diet, and ability to travel over land and in fresh and saltwater allows for potential establishment throughout Florida, particularly in coastal areas dominated by mangroves or salt marshes. In areas where Nile monitors are abundant, they have also attacked small pets and livestock such as chickens.
The State of Florida lists the Nile monitor as a Conditional Species, prohibiting personal possession and requiring a permit to possess or import this species by licensed dealers, public exhibitors or researchers that meet certain criteria and biosecurity measures.
Frequently Asked Questions
The Florida Fish and Wildlife Conservation Commission (FWC) currently monitors local populations of breeding Nile monitors in Miami-Dade, Palm Beach and Lee Counties. The FWC works with other agencies and organizations to assess the threat of this species and develop management strategies. Current efforts by the FWC include actively patrolling for and removing Nile monitors from known populations and responding rapidly to sightings of monitor species in new areas. Additionally, the City of Cape Coral in Lee County operates a trapping removal program for Nile monitors sighted in the area, and the federal government works to control the Nile monitor population at Homestead Air Reserve Base in Miami-Dade County.
Released pets remain a primary source of introduced species in Florida. Through the Exotic Pet Amnesty Program (EPAP), pet owners who are either unable to care for their exotic pets, such as Nile monitors, or who no longer wish to keep them can surrender them with no questions asked and without penalties, regardless of whether those pets are kept legally or illegally. The EPAP helps reduce the number of nonnative species being released into the wild by pet owners and fosters responsible pet ownership.
If you live near affected areas, you can make your yard less attractive to Nile monitors by removing excess debris and maintaining landscaping.
The FWC encourages reports of Nile monitor sightings. You can help by taking a picture, noting the location, and reporting this information using the free IveGot1 mobile app, calling IVE-GOT1 (888-483-4681), or by reporting online at IveGot1.org. Do not attempt to capture Nile monitors. Nile monitors have sharp teeth, strong jaws and sharp claws and, as with any wild animal, will defend themselves if aggravated or threatened.