Like all lizards, they don't produce their own body heat, but rely on the warmth of their surroundings to raise their body temperature. In cold weather they usually remain inactive, buried deep in their shelter sites.
When threatened, blue-tongues turn towards the threat, open their mouth wide and stick out their broad blue tongue that contrasts vividly with the pink mouth. This display, together with the large size of the head, may frighten off predators. If the threat doesn't go away, they hiss and flatten out their body, making themselves look bigger. A frightened blue-tongue can bite if it is picked up, so don't pick them up!In the bush the major predators of blue-tongues are large predatory birds (such as Brown Falcons and Laughing Kookaburras) and large snakes (including the Eastern Brown Snake, Red-bellied Black Snake and Mulga Snake). Feral cats and dogs also eat blue-tongues.
They are solitary for most of the year. In mating season, the males fight aggressively among themselves. Mating may be rough, with females carrying scrape marks from the male's teeth. Females give birth three to five months after mating. The young are ready to look after themselves straight after birth, and disperse within a few days. Up to 19 (but usually about 10) young are born in one litter.
They are long-lived. Several captive animals have lived for 20 years, and they may live much longer.
Blue-tongues are often found in suburban back yards. Unfortunately, they will eat snails and slugs poisoned by snail baits and can be poisoned themselves. Care should be taken in using snail baits and insecticides when blue-tongues are living in a garden. Blue-tongues can squeeze through small holes in and under fences, and garden pests can also cross fences, so chemicals used by neighbours can also affect your blue-tongue.
Look out for blue-tongues when mowing long grass! They will try to escape the lawn mower by hiding in the grass rather than running away. Blue-tongues like to bask on warm surfaces, and black tar roads which warm up quickly in the sun "lure" many to their deaths.
Blue-tongues are also easy prey for suburban dogs and cats, as well as predatory birds like kookaburras.