NILE (WATER) MONITOR
(Varanus niloticus)
Swahili: MBURUKENGE
A big, dark green and yellow monitor with distinctive pointed snout and long, flexible neck. The body is long, robust and cylindrical, with well-developed muscular limbs and large, strong claws. The jaws are strong and muscular, and the dark tongue is long, smooth, retractile and forked like a snake. Eyes are large with round pupils, yellow and black irises and yellow eyelids. Nostrils are round and situated mid-way between the eyes and the end of the snout. Ear openings are obvious. The tail is tough and whip-like, laterally compressed, triangular in section, with a hard vertebral ridge, and is about 60% of the total body length. It cannot be shed. The oar-like tail is used for climbing and swimming, and as a defensive weapon.
The skin is tough and leathery, with small, non-overlapping, bead-like or button-like scales in 128 to 183 rows at mid-body. Ground color is black, brown, dark olive green or grayish-green, spotted with yellow. There are 6 to 11 yellow crossbars of spots on the body. The limbs are spotted yellow on black, the flanks vertically barred or blotched green/black and yellow. The tail has 10 to 18 vertical yellow bars on a dark background. The belly and throat are dirty yellow or cream with black or dark blue crossbars or blotches. Big adults can become very dull, especially if foraging away from water
Ecology and Behavior |
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Distribution: Found throughout sub-Sahara Africa from along the Nile River in Egypt south to the Cape in southern Africa, from East Africa west to Mauritania.
Habitat: Near water sources, from sea level to 5,000 feet, especially lakes and major perennial river systems. Found on the East African coast and most of the large islands except Pemba. Only absent from high-altitude areas and the dry north and east of Kenya. Proliferation of dams in parts of Africa have provided extra habitat for monitors.
Food and Feeding Methods: Varied carnivorous diet of invertebrates, including slugs, spiders and water beetles, and small vertebrates, including frogs, fish, lizards, birds and bird eggs. Monitors are very fond of freshwater crabs and mussels, which they crush with their rounded, peg-like teeth. They are known for raiding unattended crocodile nests as well as nests of sea turtles and freshwater terrapins. They also are known to raid chicken runs. With an excellent sense of smell, they will search for and eat carrion. Food is swallowed whole or is torn to pieces with their strong claws. They forage both on land and in the water. Juveniles have sharper, recurved teeth than adults and eat mostly insects and frogs in marginal reed beds where they hunt.
Behavior: Diurnal, terrestrial and aquatic. Active in the water and on the ground, the Nile monitor also climbs trees and rocks. It is fast moving, running with a serpentine motion. Using its blade-like tail, it is a superb swimmer, with limbs tucked in, and can stay underwater for 20 minutes, though its underwater behavior has yet to be studied. When inactive, it basks or rests on waterside vegetation, trees, logs and rocks, often in a prominent position. In colder parts of South Africa, it hibernates in rock cracks but hasn’t been observed hibernating in East Africa.
Nile monitors are very wary and if approached, will run away or jump into the water, often at a considerable height. Juveniles are more cautious than adults but will not enter deep or fast-flowing water. If approached, they prefer to scramble away and hide in vegetation in shallow reed beds. If cornered, monitors will inflate their throats and hiss loudly, while raising themselves up high and stiff-legged, and lashing with their tails. If seized, they will bite savagely and scratch with their claws. Monitors are not poisonous.
Crocodiles and pythons are major predators on adult monitors.
Reproduction: The female excavates a hole in a living termite mound and lays her eggs over a period of 2 to 3 days. The termites then repair their nest, sealing the eggs inside, where they develop at a constant warm temperature and humidity. Between 20 and 60 large, soft-shelled eggs, 1 x 2 inches in size, are laid in the clutch. Incubation in East Africa is unknown but in South Africa, it takes up to a year for the young to emerge from the nest. In captivity at 86 degrees F, eggs hatch in 129 to 175 days.
Hatchlings, 9 ¾ to 13 inches in size, emerge together, digging themselves out of the rain-softened nest. In East Africa, hatchlings have been observed in southern Kenya in January, and in northern Kenya and Tanzania in July.
Status: Widest distribution of any African lizard though they may be under threat in certain parts of Africa where they are heavily exploited for their skin and meat. Widespread throughout East Africa where there are suitable water sources. Protected by CITES, Appendix II.
Remarks: The monitor family (Varanidae) includes the world’s largest lizards, ranging from Australia through Asia to Africa. Very large fossils, almost 20 feet long, are known from the Pleistocene period. Four species of monitors are found in Africa and the Nile monitor is Africa’s largest lizard.
Monitor lizards are persecuted for their skin that is sought after for leather in some countries, for their white, palatable meat and for their fat that is used for tribal medicine.
In Egypt, some people believe that they bring good luck and truck drivers often have stuffed monitors mounted on their radiator grills.
Length: Avg. 5 - 7 ft. (up to 8 ft.)