There are six species of of blue-tongue lizard, which also includes two sub-species . The belly of the blue-tongue is usually quite pale with darker variegations adorning their back. Their eyes are small and reddish-brown to grey. The tongue is dark blue and the lining of the mouth is bright pink. Blue-tongues have a long body, large head and short legs and toes. The tail is shorter than the body and generally tapers evenly to a point. Male blue-tongues may have a proportionally larger head than females
Blue-tongue lizards are found throughout most of Australia. Blue-tongues usually live in open country with lots of ground cover such as tussocky grasses or leaf litter. They shelter at night among leaf litter, in burrows and under large objects on the ground such as rocks and logs. Early in the mornings blue-tongues emerge to bask in sunny areas and will then forage for food during the warmer parts of the day. Like all reptiles, blue-tongues do not produce their own body heat, relying on the warmth of their surroundings to raise their body temperature. Blue-tongues maintain a body temperature of about 30-35°C when active. During cold weather they mostly remain inactive, buried deep in their shelter sites, only emerging to bask on sunny days.
Blue-tongues eat a wide variety of vegetation and invertebrates. Their teeth are large and they have strong jaw muscles so they can crush snail shells and beetles.
Blue-tongues live alone for most of the year, but between September and November males pursue females and mating occurs. At this time, males may fight aggressively among themselves. Mating may be rough, with females carrying scrape marks from the male's teeth. Female blue-tongues give birth to live young three to five months after mating, between December and April. The young are independent at birth, and disperse within a few days. Of all the blue-tongues, the eastern blue-tongue has the largest litters and the smallest young. Up to 25 (but usually about 10) young are born, each measuring 130-140 mm in total length and weighing 10-20g. Blue-tongues are long-lived and several captive animals have lived for 20 years.
When threatened, blue-tongues turn towards the threat, open their mouth wide and stick out their broad blue tongue, which contrasts vividly with the pink mouth. This display, together with the large size of the head, may frighten off predators. If the threat does not go away, blue-tongues may hiss and flatten out the body to make themselves look bigger.