All are covered with coarse hair and their backs have spines. Their snouts are elongated and slender. They have very short, strong limbs with large claws and are powerful diggers. Echidnas have no teeth, a tiny mouth, and a weak jaw. They feed by tearing open soft logs, anthills and the like, and using their long, sticky tongue to sweep up termites, ants and other small arthropods, which are crushed between the tongue and the roof of their mouth.
New Guinea has two or three endemic species, scientists can't quite decide yet: Zaglossus bruiini the " Long-beaked Echidna of the highland forests, the recently discovered Zaglossus attenboroughi, which prefers a still higher habitat and is called the Cyclops Long-beaked Echidna, and possibly Zaglossus bartoni, discovered in 1907 but may only be a sub-species of Zaglossus bruiini. All are rare, are hunted for food, and are in danger of extinction. They forage in leaf litter on the forest floor, eating worms and other insects.
The Short-beaked Echidna (Tachyglossus aculeatus) is found in south east New Guinea and also occurs in almost all Australian environments: from the snow-clad Australian Alps to the deep deserts: essentially anywhere that ants and termites are available. Smaller than the Zaglossus species, it has longer hair (so long in the Tasmanian form that the spines can be hidden), more spines, and a shorter beak.
It is a fairly long-lived and highly adaptable animal. In the mountains it hibernates during winter; in the arid zones it shelters in caves or rock crevices during the heat of the day and becomes active only at night; in temperate regions it is largely crepuscular, though in colder weather it will remain active all day.
Echidnas are oddly self-contained creatures. Outside of the mating season (midwinter in most areas, mainly July and August) they are solitary, occupying overlapping home ranges with no particular fixed base. They wander, presumably in seach of food, with a disctinctive side-to-side gait, usually moving very slowly, particularly if the terrain is rocky or tussocked. Their sight is poor but they are nevertheless quick enough to detect movement near them, and if disturbed by it to take protective measures: wedging themselves into any convenient hollow log or rock crevice; or disappearing into even moderately hard soil at a surprising pace, remaining horizontal all the while until only a few spines on the uppermost portion of the back are visible; or, if on very hard, flat ground, simply curling into a ball.
The female lays a single soft-shelled egg about two weeks after mating; it is thought that she deposits it directly into her pouch. Hatching takes ten days; the young then sucks milk from the pores of the two mammaries (monotremes have no nipples) and remains in the pouch for an unknown further period. The mother begins to leave the young in the burrow while she forages well before they develop spines at three months old. It is not known at what age they stop suckling, but they are not normally found until they are about twelve months old.
The Short-beaked Echidna is sparsely distributed and nowhere common; however it has a vast range, no serious predators, and there seems to be no sign of any threat to its continued survival. In contrast, the future of its long-beaked cousins in overpopulated, protein-starved New Guinea appears grim.