The Water, or Nile, Monitor is one of the three largest lizards occurring in Africa, growing to a total length of up to almost 2.5m and a weight of up to 15kg or more!
As its name suggests, this enormous lizard is very much at home in aquatic habitats (streams, rivers, pans, lakes, dams, marshes, etc.) and is an excellent swimmer, often diving beneath the water surface to hunt for prey or escape enemies. They feed predominantly on crustaceans and molluscs, but will also prey on insects, frogs, fish and the eggs of birds, tortoises and crocodiles. They’re often seen basking in the sun on rocks or logs close to the water and are very good climbers, often hibernating in the tops of trees in temperate regions like South Africa. When cornered they lash out with their long, muscular tails in self-defense, often inflicting serious damage to any bold attacker.
After the first spring rains, females dig holes in occupied termite mounds in which they lay between 20 and 60 eggs. The termites then fix the nest and the monitor eggs then develop inside it at a constant temperature and humidity. The eggs can take anything between 6 months and a year to hatch, with the young then digging themselves out of the termite mound.
In South Africa, the Water Monitor occurs along all the river systems running to the Indian Ocean north of Port Elizabeth, as well as along the rivers making up the Orange-Vaal system running to the Atlantic. North of our borders they occur widely in sub-Saharan Africa and along the Nile River into Egypt. Sadly they are a target species of the exotic pet trade.