Echidnas are egg-laying mammals in a four-species club
Spiny anteaters of the family Tachyglossidae share Australia and New Guinea with the platypus as the only living egg-laying mammals. Four echidna species survive, descended between 20 and 50 million years ago from an amphibious, platypus-like ancestor—which is why these spiky diggers can still swim.
The name may honour Echidna, the half-woman, half-snake of Greek myth, since the animal seemed part mammal and part reptile, or it may stem from the Greek word for hedgehog or sea urchin. A mid-nineteenth-century British encyclopaedia called it the hedgehog of the colonists at Sydney. The first European drawing was made in Tasmania by George Tobin, a lieutenant on William Bligh's second breadfruit voyage. Despite the resemblance, echidnas are not close kin to hedgehogs or to American anteaters.
Their spines are hairs made of keratin, the protein in claws and horn. A slender snout doubles as mouth and nose and carries electroreceptors: about 2,000 in the long-beaked species and no more than 400 in the short-beaked one of drier country, against the platypus's 40,000. Toothless, they rip open logs and anthills and lick up prey with a sticky tongue; short-beaked echidnas eat mostly ants and termites, while long-beaked ones take worms and larvae. At 33 °C their active body temperature is the second lowest of any mammal.
A female lays a single leathery egg of under two grams straight into her pouch about 22 days after mating. The young, called a puggle, hatches after ten days using an egg tooth, laps milk from two milk patches because monotremes lack teats, and leaves the pouch as spines appear after 45 to 55 days. In the breeding season, trains of up to ten males may trail one female.
Wild echidnas live about 14 to 16 years, and one captive reached 50. When alarmed they dig in or curl into a spiky ball. Feral cats, foxes, dogs and goannas hunt them, and snakes raid burrows for spineless puggles.
Source: Echidna
