Nonnatives - Nile Monitor

Nile Monitor - Varanus niloticus

 

Florida's Exotic Wildlife. Species detail.

First year: 1990

Extirpated year:

Established status: Populations are confirmed breeding and apparently self-sustaining for 10 or more consecutive years.

Estimated Florida range: 1 county  At least 10 years, 6 counties  Not reported breeding

Statewide trend: Unknown status

Nile Monitor
Photograph by Dr. Todd S. Campbell © 2003

Threats to natives: Large carnivorous species that can dig up reptile eggs (including those of crocodilians and sea turtles) and prey upon birds, mammals, frogs, lizards, snakes, fish, and crabs. Cape Coral has the largest Florida population of burrowing owls (>1,000 pairs), which might be impacted by monitors usurping their burrows and preying upon adults, nestlings, and eggs.

Species Account: The Nile monitor(Varanus niloticus) is the longest lizard in Africa, attaining a maximum total length (TL) of 243 cm (7' 11'") (Faust 2001), but the median size for adult males is 155 cm (5' 1") TL and for adult females is 134 cm (4' 5") TL (de Buffrénil et al. 1994). The Nile monitor has 6-11 light-colored body bands on a black background and a bluish black, forked tongue (Faust 2001). It has the widest range of any lizard species in Africa and is the second most commonly sold African monitor species in the United States (Faust 2001), despite the fact that its large adult size and nervous disposition make it a difficult pet to keep. Nile monitors have been observed in various parts of Florida, but the only confirmed breeding population is in Cape Coral, Lee County (Enge et al. 2004a). From April 2001 through 7 July 2003, 159 sightings or collected specimens (including hatchlings) of Nile monitors were made in Cape Coral, and since then, over 50 have been trapped during an eradication effort by Dr. Todd Campbell (Enge et al. 2004a). Prior to this, a reptile dealer claims to have collected for resale ca. 50 monitors in Cape Coral (Enge et al. 2004a). Most monitor observations have been in residential areas in southwestern Cape Coral and along the spreader canal (Enge et al. 2004a). In Africa, the species occurs along desert fringes and from grasslands to rainforests in the vicinity of rivers, swamps, ponds, lakes, seashores, and human habitations (Faust 2001). It shelters in crevices or burrows, including those of other animals. The most suitable habitats in Florida are probably mangrove swamps, edges of freshwater and saltwater marshes, and banks of rivers, canals, and lakes. This species could potentially all wetland habitats and adjacent terrestrial habitats in peninsular Florida, including residential and agricultural areas containing water (Enge et al. 2004a). In Mali and Chad, females reach sexual maturity at ca. 36 cm (14 in) snout-vent length (SVL) or 24 months of age, and ca. 50% of mature females reproduce each year (de Buffrénil and Rimblot-Baly 1999). Large females (>71.5 cm or 28" SVL) oviposit 53-60 eggs (de Buffrénil and Rimblot-Baly 1999) that apparently take 6-10 months to hatch (Faust 2001). In Africa monitors prey or scavenge for a variety of arthropods, crabs, crayfishes, mussels, gastropods, fishes, anurans, lizards, turtles, snakes, young crocodiles, eggs, birds, and small mammals, including domestic cats. In Florida, Nile monitors could impact populations of nesting birds (especially burrowing owls), gopher tortoises, nesting sea turtles, nesting American crocodiles, and other listed species (Enge et al. 2004a).

Habitats: Freshwater river or stream, Estuarine community, Exotic plant community, Low density suburban development, areas peripheral to core urban areas, and small towns

County First Year Extirpated Year Breeding status Notes
DADE 1990s

 

Not reported breeding Card Sound Road (P. E. Moler, FFWCC, Gainesville; D. Roudebush, FFWCC, Marathon; T. Crutchfield, Fort Myers, personal communications); Matheson Hammock (K. L. Krysko, Fla. Mus. Nat. Hist., Gainesville, pers. commun.); gravid female captured (R. St. Pierre, Loxahatchee, personal communication)
LEE 1990

 

Multiple sightings and ca. 100 captures or roadkills in Cape Coral (Enge et al. 2004a)
BROWARD 1994

 

Not reported breeding Multiple sightings in Coral Springs-Tamarac area (M. Lucas, Coral Springs, personal communication)
ORANGE 2003

 

Not reported breeding Lake Price photograph (FLMNH voucher)
ALACHUA 1981

 

Not reported breeding Capture in Lake Kanapaha (K. Enge, FFWCC, Quincy, personal observation)
DE SOTO 2003

 

Not reported breeding Several sightings along the Peace River near Fort Ogden, Arcadia, and Brownville (C. Clark, Punta Gorda, personal communication)
COLLIER 2000

 

Not reported breeding Several sightings along Haldeman Creek, Naples (J. Sietz, Naples, personal communication)

References

de Buffrénil, V., and F. Rimblot-Baly. 1999. Female reproductive output in exploited Nile monitor lizard (Varanus niloticus L.) populations in Sahelian Africa. Canadian Journal of Zoology 77:1530-1539.

de Buffrénil, V., C. Chabanet, and J. Castanet. 1994. Données préliminaires sur la taille, la croissance et la longévité du varan du Nil (Varanus niloticus) dans la région du lac Tchad. Canadian Journal of Zoology 72:262-273.

Enge, K. M., K. L. Krysko, K. R. Hankins, T. S. Campbell, and F. W. King. 2004a. Status of the Nile monitor (Varanus niloticus) in southwestern Florida. Southeastern Naturalist 3:571-582.

Faust, R. J. 2001. Nile monitors: everything about history, care, nutrition, handling, and behavior. Barron's Educational Series, Hauppauge, New York. 95pp.

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