PYGMY MULGA MONITOR Varanus gilleni Lucas and Frost, 1895
The Pygmy Mulga Monitor attains 30 cm and is found in drier parts of South Australia, southern Northern Territory, north-western Western Australia and Queensland near Birdsville.
An arboreal species, it is usually found in association with mulga and desert oaks or, less frequently, gum trees. Specimens retreat to cracks in trees or under bark when disturbed foraging. Diet consists principally of small lizards and some insects.
During warm weather this lizard is mainly crepuscular, being active during early morning and dusk.

The above was from the book Australian Reptiles and Frogs by Raymond Hoser and now available on a fantastic CD-Rom along with a vast amount of other information, papers and the like on reptiles, frogs and other wildlife.