For other uses, see Echidna (disambiguation).

Echidnas, sometimes called Piggibillas or spiny anteaters, are the only surviving monotremes apart from the platypus. The three surviving species belong to the Tachyglossidae family.

Description

All are covered with coarse hair and 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. A baby echidna is called a puggle.

General behavior

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 search of food, with a distinctive 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.

Few predators can overcome these defences. An experienced dog can attack the vulnerable belly of an adult caught on very hard ground (the tightly-curled ball of spines is not complete), and it is thought that goannas take the young. Surprisingly for such a rotund and clumsy creature, they swim well.

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.

Classification

Echidnas are classified into two genera. The Zaglossus genus includes two surviving species, and two extinct species known only from fossils; while only one species of the Tachyglossus genus is known.

Zaglossus genus

The two living Zaglossus species are endemic to New Guinea. Both are rare, and hunted for food. They forage in leaf litter on the forest floor, eating worms and other insects.

• The Long-beaked Echidna (Zaglossus bruijni) of the highland forests.
• The Cyclops Long-beaked Echidna (Zaglossus attenboroughi), recently discovered, and prefers a still higher habitat.

The two extinct species are:

• Zaglossus robustus, known only from fossils.
• Zaglossus hacketti, also known only from fossils.

Tachyglossus genus

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 of the Outback: essentially anywhere that ants and termites are available. Its size is smaller than the Zaglossus species. Its hair is longer: Tasmanian varieties have hair so long the spines can be hidden.

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.

Status

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.

External links

• Animal Diversity Web (http://animaldiversity.ummz.umich.edu/site/accounts/information/Tachyglossidae.html) Tachyglossidae
• Echidna Central (http://www.isidore-of-seville.com/echidnas/) web directory
• "The Enigma of the Echidna" (http://www.nwf.org/nationalwildlife/article.cfm?articleId=763&issueId=61) by Doug Stewart, National Wildlife, April/May 2003.
• New South Wales Parks and Wildlife Service (http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Echidnas) on behavior of short-beaked echidnas