Monitors are native to Africa, Asia and Australia. The Australian monitors (Varanidae) are collectively referred to as goannas and are quite varied in both size and habitats. There are about 25 species of Australian monitors. The term monitor is derived from the habit they have of standing on their back legs and looking around or monitoring their surroundings. They have forked tongues like snakes and unlike some other lizards they cannot regrow lost tails or limbs. Australia’s largest monitor is the Perentie monitor which can grow in excess of two metres in length. Sand, Lace and Yellow-spotted monitors can grow as long as 2 metres also. These monitors have strong limbs and powerful tails; and they walk with a swaggering gait. They have very sharp claws and teeth and are also thought to have toxin glands in their mouths which inhibit blood from coagulating and induce infections. They will not intentionally attack humans but if interfered with or cornered will try to escape and can do damage to people in those circumstances.
Most monitors look fairly similar apart from the obvious size variations and some species have adaptations to suit their particular habitats. The canopy goanna and the emerald monitor have prehensile tails (tails that are adapted to grasp) to assist in arboreal activities and the Merten’s and Mitchell’s water monitors have flattened tails to assist in swimming.
The group monitor lizards also contains the world’s largest living lizard, the Komodo Dragon (Varanus komodoensis) from Indonesia which grows to more than 3 m. The Komodo Dragon is most closely related to the Lace Monitor (Varanus varius) and there is fossil evidence suggesting that Komodo Dragons once also occurred in Australia.
All the monitors are carnivorous and will eat anything that they can overpower and swallow including other reptiles, amphibians, birds, eggs, insects and small mammals. They have the ability to detach their jaw to enable eating larger prey. Larger monitors will tackle venomous snakes. They will also take carrion, of any size including dead stock.