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Nile Monitor Lizards


Monitor lizards, of the genus Varanus, are medium-to-large carnivorous lizards that can either be terrestrial or arboreal, depending on the species. Diversity of monitors is highest in Australia to southern Asia. The largest lizard (by girth not length) in the world is the Komodo Monitor (Varanus komodensis), often referred to as the Komodo dragon. Nile Monitors (Varanus niloticus) have been seen on Sanibel Island. They are native to Africa and can exceed six feet in length.

Monitor lizards are imported regularly for the pet trade and many species are bred in captivity. Nearly half of the approximately 60 monitor species in the world are kept as pets in the United States. Many species are highly prized in the pet trade and sell for over $1,000. However, the Nile monitor is an inexpensive large monitor species that is considered expendable because of their over-availability and cheap price (about $30 retail). Another reason for their low price is their “wild” temperament, which is unlike many monitor species kept in captivity that are easily tamed and do not pose a threat to their owner.

Nile monitors have been documented in Cape Coral, FL since 1990. That population was estimated to be greater than 1,000 animals in 2005. This exotic and invasive species is established and reproducing in southwest Cape Coral and its range has expanded to Pine Island, Punta Rassa and Sanibel. The Florida Fish & Wildlife Conservation Commission (FFWCC) has passed a new law (Reptiles of Concern) that takes effect on January 1, 2008. No person is able to own a Nile Monitor and four other exotic reptiles (three species of python and one anaconda) in Florida without having a $100 annual permit. This permit was created to deter impulse purchases and to allow the state to monitor how many people keep these animals. All Reptiles of Concern must have a microchip installed so any escaped or released reptiles can be identified. You must be 18 years old and fill out a knowledge-based questionnaire.

The first documented sighting (documented in a picture) of a Nile monitor on Sanibel was in the Heron’s Landing subdivision in 2005. After many failed attempts to capture this animal -- and having received consistent calls from Heron’s Landing residents as to its whereabouts over the past two years -- we believed that the lizard was “staying put.”

The video filmed on June 25, 2007 by the Sanibel Police Department showing a Nile monitor on Periwinkle Way, proved that a monitor was seen in a place other than Heron’s Landing. This could be the same monitor from the west end of Sanibel, but it is unlikely.

In early July 2007, an employee of SCCF spotted a Nile monitor travelling east across the entrance to Gulf Pines subdivision. These two occurrences within weeks of each other really got the attention of the City of Sanibel, J.N. “Ding” Darling NWR, and SCCF. We cannot say that the population is established on Sanibel since no eggs, nests or juveniles have been seen on the island but it is a possibility. Nile monitors are able to swim across Pine Island Sound to reach Sanibel but this may only be males that are expanding their home range or seeking new territory.

Regardless, these animals pose a very serious threat to the native fauna on Sanibel. Its diet in Cape Coral comprises mostly insects, amphibians, reptiles and also birds. To date, three Burrowing Owls (a Florida Species of Special Concern) have been documented as being eaten by Nile monitors in Cape Coral.

Sanibel is a very different place. We do not know what the ecological impacts of Nile monitors on Sanibel Island will be. With a greater diversity of birds, reptiles and amphibians, one can only guess as to how this predator will adapt. With sea turtle nests, bird rookeries and the endangered Sanibel Rice Rat (Oryzomys palustris sanibeli) trying to survive changes in our environment, we cannot afford an exotic predator whose role in the ecosystem can only be guessed.

An effort must be made now to eradicate this exotic lizard before it becomes numerous and cannot be totally eliminated. If you see a Nile monitor on Sanibel, please call the Sanibel police.  If you would like to support an eradication program, please contact your state and federal legislative contacts and request funding

If you have questions about Nile monitor lizards on Sanibel, please contact Brad Smith or Chris Lechowicz in Wildlife Habitat Management, 472-3984. Any pictures of Sanibel monitor lizards should be sent to Chris Lechowicz, clechowicz@sccf.org.