Nile Monitor Carcass Found - June 16, 2008

In June 14, 2008, Sanibel Police responded to a call of a possible dead alligator floating in an inland lake on Surf Sound Court, off of Rabbit Road and adjacent to the Sanibel River. Upon arrival, Sanibel Police contacted the City’s Exotic Lizard Control contractor who confirmed the animal to be a 6-foot, 30 to 40 pound Nile Monitor Lizard. The carcass has been frozen and scheduled for a necropsy. Results of the necropsy will be provided as soon as they are available.

The recovery of this Nile Monitor Lizard reconfirms that there is an established population of Nile Monitor Lizards on Sanibel Island. There have been two other confirmed Nile Monitor Lizard sightings on Sanibel Island in months previous to recovering this carcass. Last year, the City of Sanibel launched an Exotic Lizard Management Program to manage the Green Iguana (Iguana Iguana) and the Nile Monitor Lizard (Varanus Niloticus.) Both species are invasive exotics not native to Sanibel Island. Since September 2007, the City of Sanibel has removed a total of 750 Green Iguanas (312 in 2007 and 438 to date 2008).

Nile Monitor Lizards, which are native to Africa, can reach lengths upwards of 7 feet in length. These lizards usually live on vacant lots along vegetated canal banks where they can evade capture by diving into an adjacent burrow or canal. They are extremely good swimmers and may remain submerged for up to an hour. These lizards have a high reproductive rate and may lay as many as 84 eggs in a single clutch with the average being around 60 eggs. Their high reproductive rate coupled with a lack of predators to keep them in-check, make them a very serious threat to the island's wildlife. Although they look similar to another unwanted invader the green iguana, they are easily distinguishable by their elongated head, lack of spiny crest and dorsal spines.

A major danger for Sanibel is that Nile Monitor Lizards are particularly fond of eggs including those of birds and gopher tortoises and could greatly impact their populations. They climb very well allowing them to invade bird rookeries completely destroying their nests, and as an exotic it could interfere with the population balance of wildlife on Sanibel. The Nile Monitor Lizard is an omnivorous predator and will readily consume almost anything that will fit in their mouth such as snails, clams, crabs, fish, amphibians, reptiles, and mammals, including domestic pets. In addition, large Nile Monitor Lizards may also pose a threat to small infant humans if left unattended.

Green Iguanas have a spiny crest on their neck and back and adults have a loose hanging flap of skin under their chin called a “dewlap” that also has a serrated crest. Full-grown Green Iguanas are usually between four and six feet in length, including the tail, which can make up about half the body length. Green Iguanas can vary greatly in color. Adults are more uniform in color while young may appear blotchy or banded, between green and brown. Green Iguanas in Florida eat shrubs, trees, landscape plants, orchids, and fruits such as figs, mangos, berries and tomatoes. Ornamental vegetation can be decimated by one large Iguana taking up residence in a yard. In addition to destroying landscaping efforts, Iguanas also cause problems by digging nesting burrows that can undermine sidewalks, sea walls and foundations. Iguana feces are odiferous, unsightly, and may harbor Salmonella bacteria. Because Iguanas often prefer to defecate in or around water, it is not uncommon for an Iguana to use a private pool as a defecation area. Large adults may be aggressive towards people and pets if they feel threatened. Adult Iguanas spend most of their time high above ground in trees overhanging salt or freshwater sources, such as bays, lakes, ponds, or rivers so when threatened by a predator they can dive into the water and swim swiftly away. Green Iguanas have a high reproductive rate with a single clutch producing up to 65 eggs. The incubation time for the eggs is about 12-16 weeks.

Citizens of Sanibel are being asked to help eliminate these exotic lizards imminent threat to the Island's wildlife. If you see what appears to be a Nile Monitor Lizard or Green Iguana, keep the animal in your sight if possible and contact the Sanibel Police Department at the non-emergency number (239) 472-3111. The Sanibel Police Department field confirm the lizard sightings. Iguana sightings are forwarded to the City’s licensed trapper. Due to the potential environmental threat from Monitor Lizards, as well as their characteristic of moving quickly through a large territory, the City’s Natural Resource and Police Departments prioritize Nile Monitor Lizard sightings.

Green Iguana

Nile Monitor Lizard

If you have any questions regarding the City of Sanibel’s Nile Monitor Lizard or Iguana Management Program please contact the Department of Natural Resources at 472-3700.