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| Tachyglossus aculeatus|
This species is the only member of the genus Tachyglossus. The Short-beaked Echidna is covered in fur and spines. It has a special nose (snout) and a special tongue that lets the echidna catch its prey at a great speed. Like the other monotremes, the Short-beaked Echidna lays eggs. The monotremes are the only mammals that lay eggs.
The echidna lives throughout Australia, and in coastal and highland regions of southwestern New Guinea. In Australia, it is the most widespread native mammal. It is not threatened with extinction, but human activities, such as hunting, habitat destruction, and the introduction of foreign predators and parasites, have reduced the places where it lives.
The Short-beaked Echidna, first described in 1792, is called Tachyglossus aculeatus. The name Tachyglossus means "quick tongue". This is about the speed with which the echidna uses its tongue to catch ants and termites. The word aculeatus means "spiny" or "having spines".
The Short-beaked Echidna is the only member of its genus, sharing the family Tachyglossidae with the surviving three species of the genus Zaglossus that live in New Guinea. The Zaglossus species includes the:
These are all bigger than T. aculeatus. They eat mostly worms and grubs, rather than ants and termites. Species of the Tachyglossidae are egg-laying mammals; together with the related family Ornithorhynchidae, the Platypuses, they are the only living monotremes.
There are five subspecies of the Short-beaked Echidna, each live in different areas. The subspecies are also different from each other as to hairiness, spine length and width, and the size of the claws on their back feet.
- T. a. multiaculeatus on Kangaroo Island;
- T. a. setosus on Tasmania and some islands in Bass Strait;
- T. a. acanthion in Northern Territory and Western Australia;
- T. a. aculeatus in Queensland, New South Wales, South Australia and Victoria;
- T. a. lawesii in coastal regions and the highlands of New Guinea, and possibly in the rainforests of Northeast Queensland.
Short-beaked Echidnas are usually 30 to 45 centimetres in length. They have a 75-millimetre beak, and weigh between two and five kilograms. The Tasmanian subspecies, T. a. setosus, is larger than the Australian mainland species.
Because the neck cannot be seen, the head and body appear to join together. The earholes are on either side of the head, with no external pinnae. The eyes are small and at the base of the wedge-shaped beak. The nostrils and the mouth are at the far end of the beak.
The body of the Short-beaked Echidna is, except for the underside, face and legs, covered with cream-coloured spines. The spines, which may be up to 50 mm long, are modified hairs, mostly made of keratin. They have fur between the spines, which ranges in colour from honey to a dark reddish-brown and even black. The underside and short tail are also covered in fur. Fur colour changes with geographic location. The Echidna's fur may be infested with what is said to be the world's largest flea, Bradiopsylla echidnae, which is about 4 mm long.
The legs of the Short-beaked Echidna are designed for rapid digging. Their legs are short and have strong claws. The claws on the back feet are longer and curve backwards to help cleaning and grooming between the spines. Like the platypus it has a low body temperature — between 30 and 32 °C. Unlike the platypus, which shows no evidence of torpor or hibernation, the body temperature of the echidna may fall as low as 5 °C. The Echidna does not pant or sweat and normally seeks shelter in hot conditions. In autumn and winter the Echidna shows periods of torpor or deep hibernation. Because of the low body temperature of the Short-beaked Echidna, it becomes sluggish in very hot and very cold weather.
The muscles of the Short-beaked Echidna have a number of unusual features. There is an enormous muscle that is just beneath the skin and covers the entire body. By contraction of various parts of this muscle the Short-beaked Echidna can change shape. The most common shape change is achieved by rolling itself into a ball when threatened, protecting its belly and presenting a defensive array of sharp spines. It has one of the shortest spinal cords of any mammal, extending only as far as the thorax.
The mouth of the Short-beaked Echidna cannot open wider than 5 mm.
The tongue of the Short-beaked Echidna is the animal's only way of catching prey. It can stick out up to 180 mm outside the snout. The tongue is sticky because of the presence of glycoprotein-rich mucous. This mucus both lubricates movement in and out of the snout and helps to catch ants and termites, which stick to it. Sticking out the tongue is achieved by contracting the circular muscles that change the shape of the tongue and force it forward, and contraction of two muscles attached to the caudal end of the tongue and to the mandible. The protruded tongue is stiffened by the rapid flow of blood, allowing it to penetrate wood and soil. Retraction requires the contraction of two internal muscles. When the tongue is retracted, the prey is caught on backward-facing keratinous "teeth" along the roof of the buccal cavity. This allows the animal to both capture and grind food. The tongue moves with great speed, and has been measured to move in and out of the snout 100 times a minute.
Many physiological adaptations fit the lifestyle of the Short-beaked Echidna. The animal burrows, and it can tolerate very high levels of carbon dioxide in inspired air. It will voluntarily remain in situations where carbon dioxide concentrations are high. Its ear is sensitive to low-frequency sound, which may be ideal for detecting sounds emitted by termites and ants underground. The leathery snout is covered in mechano- and thermoreceptors. These receptors provide information about the surrounding environment. The Short-beaked Echidna has a well-developed olfactory system, which may be used to detect mates and prey, and its other senses perform well. The brain and central nervous system of the Short-beaked Echidna have been extensively studied for evolutionary comparison with placental mammals.
The Short-beaked Echidna has the largest prefrontal cortex with respect to body size of any mammal. It shows rapid eye movement during sleep, and its brain has been shown to contain a claustrum that is similar to placental mammals, linking this structure to their common ancestor.
Like all monotremes, the echidna has only one orifice for the passage of faeces, urine and reproductive products, which is known as the cloaca. The gestating female has a pouch on its underside, where it raises its young.
The laying of eggs and the cloaca are basal traits which are present in all early amniotes, including reptiles, birds and early mammals. During courtship — observed for the first time in 1989 — males locate and pursue females. Trains of up to ten males may follow a single female in a courtship ritual that may last for up to four weeks; the duration of the courtship period varies with location. In cooler parts of their range, such as Tasmania, females may mate within a few hours of from hibernation.
Before , the male smells the female, paying particular attention to the cloaca. The male is often observed to roll the female onto her side and then assumes a similar position so that the two animals are abdomen to abdomen.
Fertilisation occurs in the oviduct. Gestation takes between 21 and 28 days, during which time the female constructs a nursery burrow. Following the gestation period, a single rubbery-skinned egg between 13 and 17 millimetres in diameter is laid directly into a small, backward-facing pouch that has developed on her abdomen. Ten days after it is laid, the egg hatches within the pouch. The embryo develops an "egg tooth" during incubation, which it uses to tear open the egg; the tooth disappears soon after hatching.
Hatchlings are about 1.5 cm long and weigh between 0.3 and 0.4 grams. After hatching, young Echidnas are known as puggles. The way in which puggles drink the milk is not yet known, but they have been observed drinking large amounts during each feeding period, since mothers may leave them unattended in the burrow for between five and ten days. The principal components of the milk are types of lactose. The milk has a high iron content, which gives it a pink colour.
Juveniles are eventually ejected from the pouch at around two to three months of age, because of the continuing growth in the length of their spines. Suckling gradually decreases until juveniles are weaned at about six months of age. The duration of lactation is about 200 days, and the young leave the burrow between 180 and 240 days.
The age of sexual maturity is uncertain, but may be four to five years. A twelve-year field study, published in 2003, found that the Short-beaked Echidna reached sexual maturity between five and 12 years of age, and that the frequency of reproduction varies from once every two years to once every six years. The Short-beaked Echidna can live as long as 45 years in the wild.
Ecology and behaviour
No systematic study of the ecology of the Short-beak Echidna has been published. There have been studies of several aspects of their ecological behaviour. Short-beaked Echidnas live alone and apart from the burrow created for rearing young; they have no fixed shelter or nest site. They do not have a home territory, but range over a wide area. Short-beaked Echidnas are usually active in the daytime; however, they have problems in hot weather, because they have no sweat glands and do not pant. Therefore, in warm weather they change their pattern of activity, becoming crepuscular (active at dawn or dusk) or nocturnal (active in the night). They can tolerate cold temperatures, and hibernate during the winter in very cold regions.
Short-beaked Echidnas can live anywhere where there is a good supply of food. Short-beaked Echidnas find food by smell, using sensors in the tip of their beak, and regularly feast on ants and termites. They are powerful diggers, using their clawed front paws to dig out prey and dig burrows for shelter. They may rapidly dig themselves into the ground if they cannot find cover when in danger.
In Australia they are most common in forested areas where there are many termite-filled fallen logs. In agricultural areas, they are most likely to be in uncleared scrub; they may be in grassland, arid areas, and in the outer suburbs of the capital cities. Little is known about their distribution in New Guinea. They have been found in southern New Guinea between Merauke in the west, to the Kelp Welsh River, east of Port Moresby, where they may be in open woodland.
The Short-beaked Echidna is common in most of temperate Australia and lowland New Guinea, and is not listed as endangered. In Australia, the number of Short-beaked Echidnas has been less affected by land clearing than have some other species, since Short-beaked Echidnas do not require a specialised habitat beyond a good supply of ants and termites. Despite their spines, they are eaten by birds, the Tasmanian Devil, cats, foxes and dogs. They were also eaten by indigenous Australians and the early Europen settlers of Australia. The most common threats to the animal in Australia are cars and habitat destruction. These have led to localised extinction. Infection with the introduced parasite Spirometra erinaceieuropaei is fatal for the Echidna. The Wildlife Preservation Society of Queensland runs an Australia-wide survey called Echidna Watch to monitor the species in Australia.
Captive breeding is difficult, partly because of the relatively infrequent breeding cycle. Only five zoos have managed to breed a captive Short-beaked Echidna, but no captive-bred young have survived to be adults. This has conservation implications for the endangered species of echidna from the genus Zaglossus, and to a lesser extent for the Short-beaked Echidna.
Short-beaked Echidnas feature in the animistic culture of Indigenous Australians, including their visual arts and stories. The species was a totem for some groups, including the Noongar people from Western Australia, who called the animal the Nyingarn. Many groups have myths about the animal; one myth explains that it was created when a group of hungry, young men went hunting at night and stumbled across a wombat. They threw spears at the wombat, but lost sight of it in the darkness. The wombat adapted the spears as its own defense and turned into an Echidna. Another story tells of a greedy man that kept food from his tribe; warriors speared him and he crawled away into the bushes, where he was turned into an Echidna, the spears becoming his spines.
The Short-beaked Echidna is an iconic animal in modern Australia. It appears on the Australian five-cent piece (the smallest denomination) and on a $200 commemorative coin released in 1992. The Short-beaked Echidna has been included in several postal issues: it was one of four native species to appear on Australian postage stamps in 1974, where it was the 25 cent stamp; it appeared on a 37 cent stamp in 1987, and again in 1992 when it was on the 35 cent stamp. The anthropomorphic Echidna Millie was a mascot for the 2000 Summer Olympics.
Citations in the article
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- Flannery T. 1990. Mammals of New Guinea Robert Brown. ISBN 1-86273-029-6
- Griffiths, M.E. 1978. The Biology of Monotremes. Academic Press : New York ISBN 0-12-303850-2
- Dawson T.J., Grant T.R. and Fanning D. 1979. Standard metabolism of monotremes and the evolution of homeothermy. Australian Journal of Zoology 27:511 - 515
- Hassiotis M., Paxinos G. and Ashwell K.W.S. 2004. Anatomy of the central nervous system of the Australian echidna. Proceedings of the Linnean Society of New South Wales 125:287-300
- Murray P.F. 1981. A unique jaw mechanism in the echidna, Tachglossus aculeatus (Monotremata). Australian Journal of Zoology 29: 1–5
- Doran G.A. and Baggett H. 1970. The vascular stiffening mechanism in the tongue of the echidna (Tachyglossus aculeatus). Anatomical Record 167: 197–204
- Iggo A., McIntyre A.K. & Proske U. 1985. Responses of mechanoreceptors and thermoreceptors in skin of the snout of the echidna Tachyglossus aculeatus. Proceedings of the Royal Society of London B 223: 261–277
- Burke D. 2002. Win-shift and win-stay learning in the short-beaked echidna (Tachyglossus aculeatus). Animal Cognition 5:79 - 84
- Nicol S.C. et al. 2000. The echidna manifests typical characteristics of rapid eye movement sleep. Neuroscience Letters 283:49-52
- Ashwell K.W.S., Hardman C.D. and Paxinos G. 2004. The claustrum is not missing from all monotreme brains. Brain Behaviour and Evolution 64:223-241 PMID 15319553
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- Nicol S.C., Andersen N.A. and Jones S.M. 2005. Seasonal variations in reproductive hormones of free-ranging echidnas (Tachyglossus aculeatus): interaction between reproduction and hibernation. General and Comparative Endocrinology 144: 204–210
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- Rismiller P.D. and McKelvey M.W. 2003. Body mass, age and sexual maturity in short-beaked echidnas, Tachyglossus aculeatus. Comparative Biochemistry and Physiology. A, Molecular & Integrative Physiology 136:851-865
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- Robinson, R. 1966. Aboriginal Myths and Legends. Sun Books, Melbourne
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|Wikispecies has information on: Tachyglossus aculeatus.|
- Tasmanian Department of Water, Primary Industries and Environment - Short-beaked Echidna
- Echidna Love Trains, article with sound clips and images of puggles
- Wildlife Preservation Society of Queensland - Echidna Watch
- Australian Mammal Species Files