Along with platypuses, echidnas are the only egg-laying mammals.

Life span
They are long-lived - reaching up to 49 years in captivity.

Statistics
Head-body length: 30-45cm, Weight: 2.5-8kg. Males are 25 per cent larger than females.

Physical description
Echidnas have a light-brown coat with spines on the back and sides. The spines are made of hair. They have a long, tubular, hairless snout and a short blunt tail. Males have a horny spur on the ankle of their hind himbs.

Distribution
They live on mainland Australia, Tasmania and New Guinea. The short-beaked echidna is possibly Australia's most widely distributed mammal.

Habitat
They inhabit virtually all types of habitat in their range.

Diet
Echidnas feed on ants and termites. They use their long, sticky tongue (18cm from tip of snout) to collect prey.

Behaviour
They are solitary, except during the breeding season. Their home ranges vary according to the availablity of resources in their habitat. Activity varies according to temperature. They are ususally active at dawn and dusk, but in the summer they are typically nocturnal and during the winter they may be active in the middle of the day. When inactive, they rest in hollow logs and in dense vegetation. Those inhabiting montane ranges hibernate during cold spells.

When threatened, echidnas roll up in a ball or dig a hole so that only their spines are exposed.

Reproduction
During the breeding season, females leave a scent trail. Males will then follow her in a train, sometimes of up to six. Females have a gestation period of 14 days.

The pouch is difficult to see for most of the year, but folds of skin and muscle on the sides of the abdomen enlarge during the breeding season. Echidnas have milk patches rather than teats.

The female lays a leathery egg by lying on her back and extending her cloaca (outlet into which the intestinal, urinary and genital tracts open) into the pouch. The egg hatches after 10 days and the puggle (baby echidna) stays there until it begins to grow spines. When it is old enough, she leaves it in a nursery burrow while she forages. The puggle becomes independent after 12 months.

Conservation status
The Kangaroo Island subspecies (T.a.multiaculeatus) is listed as Lower Risk/Near Threatened. Echidnas are hunted as food.

Notes
Echidnas have a very good sense of hearing and smell. Their closest relatives are duck-billed platypuses.

Records
Echidnas and platypuses have the lowest body temperatures of any mammal, around 30 degrees centigrade, which also fluctuates a lot.