Nile monitor

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Nile monitor
Nile Monitor (Varanus niloticus) (6041517538).jpg
Nile Monitor (Varanus niloticus) juvenile (16622461748).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Lacertilia
Family: Varanidae
Genus: Varanus
Subgenus: Polydaedalus
Species: V. niloticus
Binomial name
Varanus niloticus
(Linnaeus, 1758)
Nile monitor (varanus niloticus) distribution map.png
Nile monitor range
  • Lacerta monitor Linnaeus, 1758
  • Lacertus tupinambis Lacépède 1788
  • Lacerta capensis Sparrman 1783
  • Lacerta nilotica Linnaeus, 1766
  • Tupinambis elegans Daudin 1802
  • Tupinambus ornatus Daudin 1803
  • Monitor niloticus Lichtenstein 1818
  • Monitor pulcher Leach 1819
  • Stellio saurus Laurenti 1768
  • Varanus niloticus Mertens 1942
  • Varanus (Polydaedalus) niloticus ornatus Mertens 1942
  • Varanus (Polydaedalus) ornatus BÖHME & ZIEGLER, 1997

The Nile monitor (Varanus niloticus) is a large member of the monitor lizard family (Varanidae) found throughout much of Africa but absent from the west where it is replaced by Varanus stellatus.[2] Other common names include the African small-grain lizard,[3] water leguaan[4] or river leguaan (leguan, leguaan, and likkewaan mean monitor lizard in South African English, and can be used interchangeably).[5]


Nile monitors can grow to about 120 to 220 cm (3 ft 11 in to 7 ft 3 in) in length, with the largest specimens attaining 244 cm (8 ft).[6][7] In an average-sized specimen, the snout-to-vent length will be around 50 cm (1 ft 8 in).[8] In body mass, adults have been reported to vary widely, one study claiming only 0.8 to 1.7 kg (1.8 to 3.7 lb), others state weights ranging from 5.9 to 15 kg (13 to 33 lb) in big monitors. Variations may be due to age or environmental conditions.[9][10][11] Exceptionally large specimens may scale as much as 20 kg (44 lb), but this species weighs somewhat less on average than the bulkier rock monitor.[12] They have muscular bodies, strong legs, and powerful jaws. Their teeth are sharp and pointed in juvenile animals and become blunt and peg-like in adults. They also possess sharp claws used for climbing, digging, defense, or tearing at their prey. Like all monitors, they have forked tongues, with highly developed olfactory properties. The Nile monitor has quite striking, but variable, skin patterns, as they are greyish-brown above with greenish-yellow barring on the tail and large, greenish-yellow rosette-like spots on their backs with a blackish tiny spot in the middle. Their throats and undersides are an ochre-yellow to a creamy-yellow, often with faint barring.[12]

Their nostrils are placed high on their snouts, indicating these animals are highly aquatic. They are also excellent climbers and quick runners on land. Nile monitors feed on fish, snails, frogs, crocodile eggs and young, snakes, birds, small mammals, insects, and carrion.They are also the second largest reptile in the Nile river.


Nile monitors are native to Africa and the species is distributed throughout the entire central and southern regions of the continent, including Sudan and a portion of central Egypt along the Nile river.[13] They are not found in any of the desert regions of Africa, however, as they thrive around rivers.[14][15]

Invasive species

In Florida, established breeding populations of Nile monitors have been known to exist in different parts of the state since at least 1990.[16] The vast majority of the established breeding population of the species is in Lee County, Florida, particularly in the Cape Coral and surrounding regions, including the nearby barrier islands (Sanibel, Captiva, and North Captiva), Pine Island, Fort Myers, and Punta Rassa. Established populations also exist in adjacent Charlotte County, especially on Gasparilla Island.[15] Areas with a sizeable number of Nile monitor sightings in Florida include Palm Beach County just southwest of West Palm Beach along State Road 80.[17] In July 2008, a Nile monitor was spotted in Homestead, a small city southwest of Miami.[18] Other sightings have been reported near Hollywood, Naranja, and as far south as Key Largo in the Florida Keys.[17] The potential for the established population of Nile monitors in Lee, Charlotte, and other counties in Florida, to negatively impact indigenous crocodilians (American alligator, Alligator mississippiensis, and American crocodile, Crocodylus acutus) is enormous, given that they normally raid crocodile nests, eat eggs, and prey on small crocodiles in Africa. Anecdotal evidence indicates a high rate of disappearance of domestic pets and feral cats in Cape Coral.[15]

In captivity

Nile monitors are beginners; they are often found in the pet trade. Nile monitors require a medium cage. Because of their decent size, adults are likely to need custom-built quarters. Soil, sand, or bark chippings can be used as substrate. The enclosure should contain things to make a suitable habitat such as rocks, driftwood, plastic plants or hollow logs. A water dish large enough for the lizard to soak in should be used. Nile monitors have a tendency to defecate in the water dish, which thus requires frequent cleaning.

Nile monitors should have a daytime temperature gradient of about 27–32 °C (81–90 °F) and a night time temperature of about 26–27 °C (79–81 °F). A basking spot of approximately 50 °C (122 °F) should be provided at least 12 hours a day. A thermometer can be used to verify the temperature. The humidity should be moderate.

This species is very hardy in captivity when properly maintained. Wild caught animals should be checked for internal parasites.

Albino (amelanistic) specimens have been found in the wild, but there is no evidence that they have ever been propagated in captivity.


  1. IUCN Red List and search for Varanus niloticus
  2. Dowell, S.A, D.M. Portik, V. de Buffrenil, I Ineich, E Greenbaum, S.O. Kolokotronis and E.R. Hekkala. 2015. Molecular data from contemporary and historical collections reveal a complex story of cryptic diversification in the Varanus (Polydaedalus) niloticus Species Group. Molecular Phylogenetics and Evolution. doi:10.1016/j.ympev.2015.10.004
  3. "Synonyms of Nile Monitor (Veranus niloticus)". Encyclopedia of Life. Retrieved 15 December 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. Varanus niloticus, The Reptile Database
  5. "leguan - definiton". Oxford Dictionaries. Oxford University Press. Retrieved 17 December 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. Nile Monitor Care Sheet
  7. Enge, K. M., Krysko, K. L., Hankins, K. R., Campbell, T. S., & King, F. W. (2004). Status of the Nile monitor (Varanus niloticus) in southwestern Florida. Southeastern Naturalist, 3(4), 571-582.
  8. "Varanus niloticus". Monitor Lizards – Captive Husbandry. Retrieved 15 December 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. Condon, K. (1987). A kinematic analysis of mesokinesis in the Nile monitor (Varanus niloticus). Experimental biology, 47(2), 73.
  10. Hirth & Latif 1979
  11. "ANIMALS - Varanus niloticus". Dr. Giuseppe Mazza's Photomazza. Retrieved 2013-06-06.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. 12.0 12.1 "Nile Monitors". L. Campbell's Herp Page. Retrieved 2013-06-06.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  13. (Schleich et al., 1996; Spawls et al., 2002).
  14. Reptile Specialists (Nile monitor)
  15. 15.0 15.1 15.2 "NAS - Invasive Species FactSheet: Varanus niloticus (Nile monitor)". Nonindenous Aquatic Species. USGS Nonindigenous Aquatic Species Database. Gainesville, FL: United States Geological Survey. Archived from the original on 2009-05-09. Unknown parameter |dead-url= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  16. (Campbell, 2003; Enge et al. 2004).
  17. 17.0 17.1 Everglades CISMA
  18. Hofmeyer, Erik (10 June 2008). "Homestead ARB home to diverse array of wildlife". Homestead Air Reserve Base News. Homestead Air Reserve Base. Retrieved 15 December 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>