It lives among the mangrove swamps and coastal rainforests of the southeastern part of New Guinea, feeding opportunistically on everything from birds and small mammals to eggs, other reptiles, amphibians and carrion.

It is described as an evil spirit that "climbs trees, walks upright, breathes fire, and kills men", yet the local people maintain that it gives warnings if crocodiles are nearby.

Around 15 Mya, a tectonic connection between Australia and Southeast Asia allowed the varanids to spread into what is now the Indonesian archipelago.

It inhabits the high and low canopies of the lowland rainforests and coastal mangrove swamps, sometimes venturing out of these areas during floods in the rainy seasons.

[13] Males reach a considerably larger size than females in both weight and length, and also tend to have a more robust head.

[14][15] The evolutionary development of the gular pump is functionally analogous to that of the diaphragm in mammals, which ventilates the lung independently of locomotion.

[3][14] Investigation supports the idea that gular breathing is an evolutionary development that masks the effect of Carrier's constraint.

[14] The crocodile monitor's typical reported length is less than 200 cm (79 in) with a matching body mass of about 20 kg (44 lb).

[18] The average size of crocodile monitors caught in one study was 99.2 cm (39.1 in) with a weight of 2.02 kg (4.5 lb), but these must have been young specimens.

[19] Crocodile monitors are unique among extant varanid species in that its tail is much longer than the snout-to-vent length in both juveniles and adults.

It possibly attains the greatest length among extant species of lizards, although it is considerably less massive than the Komodo dragon.

[7][22] Claims of crocodile monitors attaining large weights also are unverified; the species is much more slender than Komodo dragons of comparable length.

[6] In general crocodile monitors avoid human contact, but their bite is capable of causing infection, like the Komodo dragon's.

[3] Their upper teeth are long, fang-like, set vertically in the jawbone, adapted to hooking into fast-moving prey such as birds, bats, and rodents.

[3][29] Varanus salvadorii is currently protected under the CITES Appendix II,[30] which requires an exportation permit for international trade.

[31] It faces threats from deforestation and poaching, as it is hunted and skinned by native peoples, who consider the monitor an evil spirit that "climbs trees, walks upright, breathes fire, and kills men", to make drums.