Nile Monitor

The Nile monitor (Varanus niloticus), often referred to as water monitor or water leguaan, particularly in South Africa, is the largest lizard in Africa. It is found across almost all of sub-Saharan Africa. It can reach lengths of more than 220 cm (7 ft 3 in), although it typically averages a length of 150 cm (5 ft). Although it is the largest lizard in Africa, the bulkier rock monitor (Varanus albigularis) is a little heavier on average (with Nile monitors averaging around 6-7 kg (13-15 lb) and rock monitors averaging 6-8 kg (13-18 lb). However, the heaviest African lizard recorded is a Nile monitor that weighed 20 kg (44 lb).

The Nile monitor has a long snout, a slender body, and sharp claws which it uses for digging, climbing, defense, and attacking prey. It is prominently dark with greenish-yellow patterns on its body. The pattern varies between individuals and even more between subspecies. The pattern is typically solid bands down its tail, with spotted bands across its back and solid bands across its belly. It was once believed that the Nile monitor was separated into several species across sub-Saharan Africa, but most of these are now subspecies. One exception is the West African Nile monitor (Varanus niloticus stellatus) which recently has been suggested to be a separate species due to significant genetic differences.

The Nile monitor is generally found close to water bodies and spends a lot of time in water. It also very often seen basking in the sun on rocks and banks nearby water. As long as there is water nearby, they can be found in most habitats, such as grasslands, savannas, forests, and rainforests. They are even found in some desert regions, as long as there is nearby water. In addition to rivers and lakes across most of sub-Saharan Africa, Nile monitors are also found along the entire Nile River, all the way up north to Egypt. It was once also found along rivers and water bodies in Israel, but it is now extinct here.

The Nile monitor is a carnivorous species with a broad diet. It will eat anything as long as it is within a suitable size range. Prey can be as small as invertebrates, such as insects, spiders, earthworms, and slugs, and as large as young antelopes, and everything in between. Typical medium sized prey for a Nile monitor is small reptiles, frogs, crabs, fish, birds, and rodents. It commonly eats eggs, and will also eat carrion, human leftovers and even feces. It will hunt prey on land, in trees, underground, and in the water. It has a venomous bite, which helps in subduing and killing its prey. This venom is not deadly to humans.

Nile monitors reach sexual maturity when they reach a length of almost 1 meter (3 ft), which typically takes 2-3 years. Breeding season varies between region, but typically coincides with the rainy season. Males often fight each other for mating rights, and females may mate with several males. A female will excavate a burrow, either in the ground or in a termite mound, where she eventually lays her eggs. A clutch of 20-60 eggs is laid, and the burrow will be closed. It could take as much as 10 months to a year before the eggs hatch. After hatching the baby monitors may have to wait for rain to open up the burrow. Sometimes the mother comes to help open it. Once freed from the burrow, the baby monitors must fend for themselves.

The Nile monitor is common and widespread across much of sub-Saharan Africa. It can fair well close to human habitation, as it readily feeds on human waste. The population is believed to be stable and it is listed as least concern on the IUCN Red List.

The Nile monitor has become an invasive species in Florida, United States, where it is causing problems for native species. One such problem is the raiding of nests belonging species such as American alligator (Alligator mississippiensis) and American crocodile (Crocodylus acutus).