Nile monitor

Members of the Nile monitor species group were already well known to Africans in ancient times. For example, they were commonly caught, likely as food, in the Djenné-Djenno culture at least a millennium ago.[8]

The Nile monitor twice was given a scientific name by Carl Linnaeus: First as Lacerta monitor in 1758 in the 10th edition of Systema Naturae, the starting point of zoological nomenclature. He described it again in 1766 as Lacerta nilotica. Despite being older, the name proposed in 1758 is invalid because it was rejected in ICZN opinion 540, making the name of 1766 valid.[5][9] The genus Varanus was coined in 1820 by Blasius Merrem. Six years later Leopold Fitzinger moved the Nile monitor into this genus as Varanus niloticus,[10] the currently accepted scientific name for the species.[5]

Nile monitor eating crocodile egg, Katavi National Park

The Nile monitor is Africa's longest lizard.[13] They grow from 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).[14][15] In an average-sized specimen, the snout-to-vent length will be around 50 cm (1 ft 8 in).[16] 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.[17][18][19] 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.[20] 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.[20]

Their nostrils are placed high on their snouts, indicating these animals are very well adapted for an aquatic lifestyle. They are also excellent climbers and quick runners on land. Nile monitors feed on a wide variety of prey items, including fish, frogs, toads (even poisonous ones of the genera Breviceps and Sclerophrys),[21] small reptiles (such as turtles, snakes, lizards, and young crocodiles),[22] birds, rodents,[23] other small mammals (up to domestic cats and young antelopes [Raphicerus]),[24][25] eggs (including those of crocodiles, agamids, other monitor lizards, and birds),[22] invertebrates (such as beetles, termites, orthopterans, crabs, caterpillars, spiders, millipedes, earthworms, snails, and slugs),[23][22] carrion, human wastes, and feces.[22]

Nile monitors are native to Sub-Saharan Africa and along the Nile.[26] They are not found in any of the desert regions of Africa (notably Sahara, Kalahari and much of the Horn of Africa), however, they thrive around rivers.[27][28] Nile monitors were reported to live in and around the Jordan River, Dead Sea, and wadis of the Judaean Desert in Israel until the late 19th century, though they are now extinct in the region.[29]

Nile monitors are often found in the pet trade despite their highly aggressive demeanor and resistance to taming. Juvenile monitors will tail whip as a defensive measure, and as adults they are capable of inflicting moderate to serious wounds from biting and scratching. Nile monitors require a large cage as juveniles quickly grow when fed a varied diet, and large adults often require custom-built quarters.

"There are few lizards less suited to life in captivity than the Nile monitor. Buffrenil (1992) considered that, when fighting for its life, a Nile monitor was a more dangerous adversary than a crocodile of a similar size. Their care presents particular problems on account of the lizards' enormous size and lively dispositions. Very few of the people who buy brightly-coloured baby Nile monitors can be aware that, within a couple of years, their purchase will have turned into an enormous, ferocious carnivore, quite capable of breaking the family cat's neck with a single snap and swallowing it whole."[33]