Echidnas (Tachyglossus aculeatus), or spiny ant eaters as they are sometimes known, are familiar to most Australians. Echidnas are monotremes (mammals that lay eggs). There are only three species of monotreme in the world -- the platypus and two species of echidna, one of which is restricted to the New Guinea highlands. They have many features which are reptilian in nature such as egg laying, legs that extend outward then downward, and a lower body temperature (about 31-320C), than other mammals.
Echidnas are 30 cm to 45 cm in length and weigh between 2 kg and 5 kg with Tasmanian animals being larger than their Australian mainland counterparts. The body, with the exception of the underside, face and legs, is covered with cream coloured spines. These spines, which reach 50 mm in length, are in fact modified hairs. Insulation is provided by fur between the spines which ranges in colour from honey to a dark reddish-brown and even black. The fur of the Tasmanian subspecies is thicker and longer than that of echidnas in warmer mainland areas and therefore often conceals the spines.
The echidna is common throughout most of temperate Australia and lowland New Guinea. In Tasmania, it is particularly common in dry open country on the east coast. It is also found on open heathlands and in forests and can sometimes be seen slowly wandering along roadsides in its characteristic rolling gait.
The echidna is shy and moves slowly and carefully, but can usually be approached by treading softly. It is solitary for most of the year but at mating time several males may follow a female. Their activity patterns differ with location and temperature -- in the warmer parts of Australia it is completely nocturnal, spending the daytime resting out of the heat. They typically shelter in rotten logs, stumps or burrows, or under bushes. In more temperate areas foraging occurs around dusk, while echidnas in southern Australia are often active during the day, particularly during winter.
If disturbed, echidnas will usually lower the head, and with vigorous digging, sink rapidly into the ground leaving only the spines exposed. On hard surfaces they will curl into a ball -- presenting defensive spines in every direction. They are also capable of wedging tightly into crevices or logs by extending their spines and limbs.
Echinda Hind FootThe echidna is adapted for very rapid digging, having short limbs and powerful claws. The claws on the hind feet are elongated and curve backwards; to enable cleaning and grooming between the spines. However, despite this, they are infested with what is said to be the world's largest flea -- Bradiopsylla echidnae, which is about 4 mm long.
Surprisingly, echidnas are good swimmers, paddling about with only the snout and a few spines showing. They have been seen to cross wide beaches to swim and groom themselves in the sea.
Echidna footprintsMale echidnas, like their relative the platypus, have a spur on each hindfoot. However, unlike the platypus the spur is blunt and the venom gland is not functional.
The breeding season for echidnas is from the end of June to September. Two weeks after mating, a single rubbery-skinned egg is laid directly into a small backward facing pouch which has developed in the female. After 10 days the egg hatches and the young remains in the pouch. During the following period of lactation the female spends most of her time in a burrow but will leave the young behind, covered with soil or wood fibre, to go foraging. As echidnas lack nipples, the mammary glands secrete milk through two patches on the skin from which the young suckle. Juveniles are eventually ejected from the pouch at around 2 - 3 months of age due to the continuing growth of their spines. Suckling gradually decreases up until the juvenile is weaned at about 6 months of age.
The diet of echidnas is largely made up of ants and termites, although, they will eat other invertebrates especially grubs, larvae and worms. The strong forepaws are used to open up the ant or termite nest and the echidna then probes the nest with its sensitive snout. Any insects in the nest are caught on the echidnas rapidly moving 15 cm tongue which is covered with a layer of sticky mucous, hence the name Tachyglossus meaning 'fast tongue'. The jaws are narrow and have no teeth so food is crushed between hard pads which lie in the roof of the mouth and on the back of the tongue. Large grubs are squashed and the contents licked up. Echidnas eat a lot of soil and ant-nest material when feeding, and this makes up the bulk of droppings.
The echidna is common and widespread. They are less affected by the clearing of land as much as many other native animals as they can live anywhere that there is a supply of ants. Despite their covering of spines they do have natural predators such as eagles and Tasmanian devils which even eat the spines. They were a favourite food of Aboriginal people and early white settlers although they are now wholly protected by law.