Echidnas also known as spiny anteaters, are four extant mammal species belonging to the Tachyglossidae family of the monotremes. Together with the Platypus, they are the only surviving members of that order. Although their diet consists largely of ants and termites, they are not actually related to the anteater species. They live in New Guinea and Australia. The echidnas are named after a monster in ancient Greek mythology.
Echidnas are small mammals that are covered with coarse hair and spines. Superficially they resemble the anteaters of South America, and other spiny mammals like hedgehogs and porcupines. They have snouts which have the functions of both the mouth and nose. Their snouts are elongated and slender. They have very short, strong limbs with large claws and are powerful diggers. Echidnas have a tiny mouth and a toothless jaw. They feed by tearing open soft logs, anthills and the like, and use their long, sticky tongue which protrudes from their snout to collect their prey. The Short-beaked Echidna's diet consists largely of ants and termites, while the Zaglossus species typically eat worms and insect larvae.
The long-beaked echidnas have tiny spines on their tongues that help capture their meals.
Echidnas and the Platypus are the only egg-laying mammals, known as monotremes. The female lays a single soft-shelled, leathery egg twenty-two days after mating and deposits it directly into her pouch. Hatching takes ten days; the young echidna, called a puggle, then sucks milk from the pores of the two milk patches (monotremes have no nipples) and remains in the pouch for forty-five to fifty-five days, at which time it starts to develop spines. The mother digs a nursery burrow and deposits the puggle, returning every five days to suckle it until it is weaned at seven months.
Male echidnas have a four-headed penis, but only two of the heads are used during mating. The other two heads "shut down" and do not grow in size. The heads used are swapped each time the mammal copulates.
The two fossil species are: