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Short-beaked Echidna

2007 Schools Wikipedia Selection. Related subjects: Mammals

              iShort-beaked Echidna

                             Conservation status

   Least concern (LR/lc)
            Scientific classification

   Kingdom:  Animalia
   Phylum:   Chordata
   Class:    Mammalia
   Subclass: Prototheria
   Order:    Monotremata
   Family:   Tachyglossidae
   Genus:    Tachyglossus
             Illiger, 1811
   Species:  T. aculeatus

                                Binomial name

   Tachyglossus aculeatus
   ( Shaw, 1792)

   The Short-beaked Echidna (Tachyglossus aculeatus), also known as the
   Spiny Anteater because of its diet of ants and termites, is one of four
   living species of echidna and the only member of the genus
   Tachyglossus. The Short-beaked Echidna is covered in fur and spines and
   has a distinctive snout and a specialized tongue, which it uses to
   catch its prey at a great speed. Like the other extant monotremes, the
   Short-beaked Echidna lays eggs; the monotremes are the only group of
   mammals to do so.

   The species is found throughout Australia, where it is the most
   widespread native mammal, and in coastal and highland regions of
   southwestern New Guinea, where it is known as the Mungwe in the Daribi
   and Chimbu languages. It is not threatened with extinction, but human
   activities, such as hunting, habitat destruction, and the introduction
   of foreign predatory species and parasites, have reduced the
   distribution of the Short-beaked Echidna in Australia.

Taxonomy

   The Short-beaked Echidna was first described by George Shaw in 1792. He
   named the species Myrmecophaga aculeata, thinking it might be related
   to the South American anteater. Since Shaw first described the species,
   its name has undergone four revisions: from M. aculeata to
   Ornithorhynchus hystrix, Echidna hystrix, Echidna aculeata and,
   finally, Tachyglossus aculeatus. The name Tachyglossus means "quick
   tongue", in reference to the speed with which the Echidna uses its
   tongue to catch ants and termites, and aculeatus means "spiny" or
   "equipped with spines".

   The Short-beaked Echidna is the only member of its genus, sharing the
   family Tachyglossidae with the extant species of the genus Zaglossus
   that occurs in New Guinea. Zaglossus species, which includes the
   Western Long-beaked, Sir David's Long-beaked and Eastern Long-beaked
   Echidna, are all significantly larger than T. aculeatus, and their diet
   consists mostly of worms and grubs rather than ants and termites.
   Species of the Tachyglossidae are egg-laying mammals; together with the
   related family Ornithorhynchidae, they are the only extant monotremes
   in the world.

   There are five subspecies of the Short-beaked Echidna, each found in a
   different geographical location. The subspecies also vary from each
   other in terms of hairiness, spine length and width, and the size of
   the grooming claws on their hind feet.
     * T. a. multiaculeatus is found on Kangaroo Island;
     * T. a. setosus is found on Tasmania and some islands in Bass Strait;
     * T. a. acanthion is found in Northern Territory and Western
       Australia;
     * T. a. aculeatus is found in Queensland, New South Wales, South
       Australia and Victoria;
     * T. a. lawesii is found in coastal regions and the highlands of New
       Guinea, and possibly in the rainforests of Northeast Queensland.

Physical Description

   Short-beaked Echidnas are typically 30 to 45  centimetres in length,
   have a 75- millimetre snout, and weigh between two and five kilograms.
   However, the Tasmanian subspecies, T. a. setosus, is larger than its
   Australian mainland counterparts. Because the neck is not externally
   visible, the head and body appear to merge 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 snout. The nostrils and the mouth
   are at the distal end of the snout; the mouth of the Short-beaked
   Echidna cannot open wider than 5 mm. The body of the Short-beaked
   Echidna is, with the exception of 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. Insulation is provided by
   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. Colouration of the fur and spines varies 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 limbs of the Short-beaked Echidna are adapted for rapid digging,
   their limbs are short and have strong claws. The claws on the hind feet
   are elongated and curve backwards to enable cleaning and grooming
   between the spines. Like the Platypus it has a low body temperature —
   between 30 and 32  °C, but 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. Like all monotremes, it has one orifice for
   the passage of faeces, urine and reproductive products, which is known
   as the cloaca. The male has internal testes, no external scrotum and a
   highly unusual penis with four knobs on the tip. The gestating female
   develops a pouch on its underside, where it raises its young.
   A Short-beaked Echidna curled into a ball; the snout is visible on the
   right.
   Enlarge
   A Short-beaked Echidna curled into a ball; the snout is visible on the
   right.

   The musculature of the Short-beaked Echidna has a number of unusual
   aspects. The panniculus carnosus is an enormous muscle that is just
   beneath the skin and covers the entire body. By contraction of various
   parts of the panniculus carnosus, the Short-beaked Echidna can change
   shape—the most characteristic 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 musculature of the face, jaw and tongue is specialised to allow the
   Echidna to feed. The tongue of the Short-beaked Echidna is the animal's
   sole means of catching prey, and can protrude up to 180 mm outside the
   snout. The tongue is sticky because of the presence of
   glycoprotein-rich mucous, which both lubricates movement in and out of
   the snout and helps to catch ants and termites, which adhere to it.
   Protrusion of the tongue is achieved by contracting the circular
   muscles that change the shape of the tongue and force it forward, and
   contraction of two genioglossal 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 longitudinal
   muscles, known as the sternoglossi. When the tongue is retracted, the
   prey is caught on backward-facing keratinous "teeth", located along the
   roof of the buccal cavity, allowing the animal both to 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.

   Numerous physiological adaptations aid the lifestyle of the
   Short-beaked Echidna. Because the animal burrows, it can tolerate very
   high levels of carbon dioxide in inspired air, and 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, which 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. It has a highly sensitive optic nerve, and has been
   shown to have visual discrimination and spatial memory comparable to
   those of a rat. 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.

Reproduction

   The underside of a female Short-beaked Echidna; the pouch which carries
   her eggs is shown in the middle of the abdomen.
   Enlarge
   The underside of a female Short-beaked Echidna; the pouch which carries
   her eggs is shown in the middle of the abdomen.

   The solitary Short-beaked Echidna looks for a mate between May and
   September; the precise timing of the mating season varies with
   geographic location. Both males and females give off a strong odour
   during the mating season. 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 arousal from hibernation.

   Before mating, 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. Each mating results in the production of a single
   egg, and females are known to mate only once during the breeding
   season; each mating is successful.

   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. Hatchlings attach
   themselves to their mothers' milk areolae, a specialised patch on the
   skin that secretes milk (monotremes lack nipples). The way in which
   puggles imbibe the milk is not yet known, but they have been observed
   ingesting 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 fucosyllactose and saialyllactose;
   it is high in iron content, giving 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

   A Short-beaked Echidna on the move
   Enlarge
   A Short-beaked Echidna on the move

   No systematic study of the ecology of the Short-beak Echidna has been
   published; however, 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 typically active in the daytime;
   however, they are ill-equipped to deal with heat, because they have no
   sweat glands and do not pant. Therefore, in warm weather they change
   their pattern of activity, becoming crepuscular or nocturnal. They can
   tolerate cold temperatures, and hibernate during the winter in very
   cold regions.

   Short-beaked Echidnas can live anywhere that has a good supply of food.
   Short-beaked Echidnas locate food by smell, using sensors in the tip of
   their snout, and regularly feast on ants and termites. They are
   powerful diggers, using their clawed front paws to dig out prey and
   create 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
   abundant termite-filled fallen logs. In agricultural areas, they are
   most likely to be found in uncleared scrub; they may be found 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 in the east, where they may be found
   in open woodland.

Conservation status

   The Short-beaked Echidna is common throughout 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 preyed on by birds,
   the Tasmanian Devil, cats, foxes and dogs. They were eaten by
   indigenous Australians and the early European settlers of Australia.
   The most common threats to the animal in Australia are motorised
   vehicles and habitat destruction, which 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 due to 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
   maturity. This has conservation implications for the endangered species
   of echidna from the genus Zaglossus, and to a lesser extent for the
   Short-beaked Echidna.
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