The perentie is a carnivorous lizard, eating a wide variety of animals such as small mammals, birds, other lizards, turtle eggs and insects (5). Like all monitors of the Varanus genus, it is able to effectively track its prey using its long tongue, which picks up chemical signals in the air. Mates may also be located in this way (10). Like other varanids, the perentie learns to recognise good locations for food and other resources, returning regularly to these sites when foraging (11). When prey is caught, it is shaken violently until dead, and then swallowed whole (5).
Monitor species are unique in their ability to run extremely fast over great distances (12). The perentie holds its legs underneath its body, walking erect like a mammal (13), and it is also able to run solely on its hind legs (6). It can reach speeds of up to 40 kilometres per hour, enabling it to catch fast-moving mammals such as rabbits. The perentie is able to do this due to its ability to expand and contract the sides of its neck, effectively making the throat behave like bellows, pumping air from the nostrils down to the lungs while it is running (12). In addition to this athletic ability, monitor lizards also have extremely good eyesight (2).
Perentie courtship resembles that of other monitors. The male perentie licks and nuzzles the female, and several copulations will take place over a few days (10). Breeding in spring to early summer, the female perentie lays one clutch of 8 to 11 eggs per year (3). Reptile eggs are vulnerable to damage due to their thin casing, and are not fully impervious to water, allowing them to be laid in the absence of open water. To protect its eggs and keep them at constant optimum temperature and humidity, the perentie lays its eggs inside a termite nest. Termites maintain the temperature and humidity of their nests with the utmost vigilance, and the conditions are ideal for perentie eggs (12).
In general, male monitor lizards are territorial and will fight other males for access to a female. During combat, males grasp each other with their forelegs while standing on their hind legs, trying to push their rival to the ground. Defensive behaviour includes lashing the tail, clawing, and hissing (10). When threatened, the perentie will often rise on its hind legs, swell its throat and hiss (5).