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 Echidna has extremely strong front limbs and claws due to its mechanical advantage. This allows it to burrow quickly with great power. As it needs to be able to survive underground, it has a great tolerance to high levels of carbon dioxide and a lack of oxygen. It has no weapons or fighting ability and repels predators by curling into a spherical ball and deterring opponent with its spines. The Echidna lacks the ability to sweat and cannot deal with heat well, so it tends to avoid daytime activity in hot weather and can swim if needed. The Echidna's snout has mechanical and electroreceptors that help it to detect what is around it, and it also has the ability to reason.
During the winter, it goes into deep torpor and hibernation to save energy and reduce metabolism, before emerging as the temperature increases to breed. Female Echidnas only lay one egg a year, and the mating period is the only time that the otherwise solitary animals meet one another; the father has no further contact with the mother after mating. After the young is born, it is only the size of a grape, but grows rapidly on the mother's milk, which is very rich in nutrients. After a period they are too large and spiky to stay in the pouch, and after around six months they leave the burrow and have no more contact with their mother.
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. Attempts to breed the Echidna in captivity have not been successful to date, with none reaching maturity. However, as the Echidna can survive merely by foraging dead logs for ants and termites, it can survive in environments with restricted resources.
Taxonomy and naming
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 occur in New Guinea. Zaglossus species, which include 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 differ from one another in their hairiness, spine length and width, and the size of the grooming claws on their hind feet.
- 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;
- T. a. multiaculeatus is found on Kangaroo Island;
- T. a. setosus is found on Tasmania and some islands in Bass Strait.
The earliest fossils of the Short-beaked Echidna date back around 15 million years ago to the Pleistocene era, and the oldest specimens were found in caves in South Australia, often together with fossils of the Long-beaked Echidna from the same period. The ancient Short-beaked Echidnas are considered to be identical to their contemporary descendants apart from the fact that the ancestors are around 10%. This "post-Pleistocene dwarfing" affects many Australian mammals. Part of the last radiation of monotreme mammals, Echidnas are believed to have evolutionally diverged from the platypus around 65 million years ago, between the Cretacious and Tertiary periods. However, the Echidna's pre-Pleistocene heritage has not been traced yet and the lack of teeth on the fossils found thus far have made it impossible to use dental evidence.
The Short-beaked Echidna was commonly called the Spiny Anteater in older books, though this term has fallen out of fashion since the Echidna bears no relation to the true anteaters. It has a variety of names in the indigenous languages of the regions where it is found. The Noongar people from southwestern Western Australia call it the Nyingarn. In Central Australia southwest of Alice Springs, the Pitjantjatjara term is tjilkamata or tjirili, from the word tjiri for spike of Porcupine Grass (Triodia irritans). The word can also mean slowpoke. In central Cape York Peninsula, it is called (minha) kekoywa in Pakanh, where minha is a qualifier meaning 'meat' or 'animal', (inh-)ekorak in Uw Oykangand and (inh-)egorag in Uw Olkola, where inh- is a qualifier meaning 'meat' or 'animal'. In the highland regions of southwestern New Guinea it is known as the Mungwe in the Daribi and Chimbu languages.
Short-beaked Echidnas are typically 30 to 45 centimetres (12 to 18 in) in length, have a 75-millimetre (3 in) snout, and weigh between 2 and 5 kilograms (4.4 and 11 lb). However, the Tasmanian subspecies, T. a. setosus, is smaller 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, approximately a 9 mm (0.4 in) diameter sphere 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 (0.2 in). 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 (2 in) 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 (0.16 in) long.
The limbs of the Short-beaked Echidna are adapted for rapid digging: they are short and have strong claws. These strong and stout limbs allow the Echidna to tear apart large logs and move paving stones, and one has been recorded moving a 13.5 kilograms (30 lb) stone; there has also been a report of a captive Echidna moving a refrigerator in the home of a scientist around the room. The power of the limbs are based on strong musculature, particularly around the shoulder and torso area. The mechanical advantage of its arm is greater than that of humans as its biceps connect the shoulder to forearm at a point further down than for humans, and the chunky humerus allows for larger areas for more muscle to form.
The claws on the hind feet are elongated and curve backwards to enable cleaning and grooming between the spines. Like the Platypus, the Echidna has a low body temperature—between 30 and 32 °C (86 and 90 °F)—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 (41 °F). The Echidna does not pant or sweat and normally seeks shelter in hot conditions. Despite the inability to sweat, the Echidna still lose water as they exhale. The snout is believed to be crucial in restricting this loss to sustainable levels, through a bony labyrinth that has a refrigerator effect and helps to condense water vapour in the breath. The Echidna does not have highly concentrated urine, and around half of the estimated daily water loss of 120 grams (4.2 oz) occurs in this manner, while most of the rest is through the skin and respiratory system. Most of this is replenished by the Echidna's substantial eating of termites—one laboratory study reported that it would ingest around 147 grams (5.2 oz) a day, most of which was water. This can be supplemented by drinking water if available, or licking morning dew from flora.
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, known as the cloaca, for the passage of faeces, urine and reproductive products. 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.
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 being achieved by rolling itself into a ball when threatened, so 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. Whereas the human spinal cord ends at the first or second lumbar vertebrae, for the Echidna it occurs at the seventh thoracic vertebra. It has been conjectured that the shorter spinal cord allows the Echidna the flexibility to wrap into a ball.
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 (7 in) outside the snout. The snout's shape, resembling a double wedge, gives it a significant mechanical advantage in generating a large moment and therefore makes it efficient for digging to reach prey or to build a shelter. 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 circular muscles that change the shape of the tongue and force it forwards and contracting 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. This is partly achieved through the elasticity of the tongue and the conversion of elastic potential energy into kinetic energy. The tongue is very flexible, particularly at the end, allowing it to bend in U-turns and catch insects attempting to flee in their twisty nests or mounds. The tongue also has an ability to avoid picking up splinters while foraging in logs; the reason for this is unknown. It can eat quickly; a specimen of around 3 kilograms (6.6 lb) can ingest 200 grams (7.1 oz) of termites in ten minutes.
The Echidna has a stomach that is quite apart from other mammals. It is devoid of secretory glands and has cornified stratified epithelium, which resembles horny skin. Unlike other mammals, which typically have highly acidic stomachs, the Echidna has low levels of acidity, almost neutral with pH in the 6.2–7.4 range. The stomach is elastic and the gastric peristalsis grinds dirt particulates and shredded insects together. The digestion occurs in the small intestine, which is around 3.4 metres (11 ft) in length. The insect exoskeletons and dirt are not digested and ejected in the waste.
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. It can dig up to a metre into the ground to retrieve ants or evade predators, and can survive with low oxygen when the area is engulfed by bushfires. The Echidna can also dive underwater, an ability that can help it to survive sudden floods. During these situations the heart rate drops to around 12 beats per minute, around one fifth of the rate at rest. This process is believed to save oxygen for the heart and brain, which are the most sensitive to such a shortage, and laboratory testing has revealed that the Echidna's cardiovascular system is similar to that of the seal.
The Echidna's optical system is an uncommon hybrid of both mammalian and reptilian characteristics. The cartilaginous layer beneath the scleral layer of the eyeball is similar to that of reptiles and avians. The small cornea's surface is keratinised and hardened, possibly an evolution to protect the Echidna from chemicals secreted by preyed insects or self-impalement when it rolls itself up, something that has been observed. The Echidna has the flattest lens of any animal, giving it the longest focal length. This similarity to primates and humans allow it to see distant objects clearly. Unlike placental mammals—including humans—the Echidna does not have a ciliary muscle to distort the geometry of the lens and thereby change the focal length and allow objects at different distances to be viewed clearly, and it believed that the whole eye distorts so that the distance between the lens and screen instead changes to allow focusing. The visual ability of an Echidna is not great and it is not known whether it can perceive colour; however, it can distinguish between black and white, and horizontal and vertical stripes. Eyesight is not a crucial factor in the animal's ability to survive as blind Echidnas are able to live healthily.
Its ear is sensitive to low-frequency sound, which may be ideal for detecting sounds emitted by termites and ants underground. The pinnae are obscured and covered by hair, mean that opponents can not grab them in an attack, and that prey or foreign material cannot enter, although ticks are known to reside there. The ear has a macula which is very large compared to other animals. It is used as a gravity sensor to orient the Echidna. The large size is speculated to be due to importance of burrowing downwards for an Echidna.
The leathery snout is keratinised and covered in mechano- and thermoreceptors, which provide information about the surrounding environment. These nerves protrude through microscopic holes at the end of the snout. It also has mucous glands on the end of the snout that act as electroreceptors. It can detect electric fields of 1.8 mV/cm—1,000 times more sensitive than humans—and dig up buried batteries. The Echidna has a series of push rods protruding from their snout. These are columns of flattened, spinous cells, with roughly an average diameter of 50 micrometres and a length of 300 micrometres. The number of push rods per square millimetre of skin is estimated to be 30–40. It is believed that longitudinal waves can be picked up and transmitted through the rods and are mechanical sensors for the Echidna. It is thought that prey can be detected by these rods.
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, particularly with its fellow monotreme, the Platypus. The average brain volume is 25 mL, similar to a cat of approximately the same size, but while the Platypus has a largely lissencephalic and smooth brain, the Echidna has a heavily folded and fissured gyrencephalic brain similar to humans, which is seen as a sign of a highly neurologically advanced animal. The cerebral cortex is thinner, the brain cells larger and more densely packed and organised in the Echidna than the Platypus, suggesting that evolutionary divergence must have occurred long ago. Almost half of the sensory area in the brain is devoted to the snout and tongue, and the part devoted to smell is relatively high compared to other animals.
The Short-beaked Echidna has the largest prefrontal cortex relative to body size of any mammal, taking up 50% of the cerebral cortex in comparison to 29% for humans. This part of the brain in humans is though to be used for planning and analytical behaviour, leading to debate as to whether the Echidna has reasoning and strategising ability. Experiments in a simple maze and with a test on whether the animal can open a trapdoor to access food, and the Echidna's ability to remember what it has learnt about the task for over a month has led scientists to conclude that its learning ability is similar to that of a cat or a rat.
The Echidna shows rapid eye movement during sleep, usually around its thermoneutral temperature of 25, and this effect is suppressed at other temperatures. Its brain has been shown to contain a claustrum similar to that of placental mammals, so linking this structure to their common ancestor.
Ecology and behaviour
No systematic study of the ecology of the Short-beaked Echidna has been published. There have, however, 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 that they defend against other Echidnas, but range over a wide area. The range area has been observed to be between 21 and 93 ha, although one study in Kangaroo island found that the animals there covered an area between 9 and 192 ha. Overall, the mean range areas across the various regions of Australia were 40–60 ha. There was no correlation between gender and range area, but a weak one with size. Echidnas can share home ranges without incident, and sometimes share shelter sites if there are not enough for or each animal to have one individually.
Short-beaked Echidnas are typically active in the daytime, though 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. Body temperatures above 34 °C (93 °F) are believed to be fatal, and in addition to avoiding heat, the animal adjusts its circulation to maintain a sustainable temperature by moving blood to and from the skin to increase or lower heat loss. In areas where water is present they can also swim to keep their body temperatures low. The "thermoneutral zone" for the environment is around 25 °C (77 °F) at which point metabolism needed to maintain body temperature is minimized. Echidnas can tolerate cold temperatures, and they hibernate during the winter both in cold regions and in regions with a more temperate climate. The Echidna is endothermic, and can maintain body temperatures of around 32°F. It can also reduce its metabolism and heart rate and body temperature. In addition to brief and light bouts of torpor throughout the year, the Echidna enters deeper periods during winter when it hibernates. During periods of hibernation, the body temperature drops to as low as 4 °C (39 °F). The heart rate falls to 4–7 beats per minute—down from 50–68 at rest&mdash, and the Echidna can breathe as infrequently as once every three minutes, 15–18 times slower than when it is active. Metabolism can drop to one eighth of the normal rate. Echidnas begin to prepare for the hibernation phase of the year between February and April, when they reduce their consumption and enter brief periods of torpor. Males begin hibernating first, while females that have reproduced start later. During the period of hibernation, the animals average 13 separate bouts of torpor, which are broken up by periods of arousal lasting 1.2 days on average. These interruptions tend to coincide with warmer periods. Males end their hibernation period in mid June, while reproductive females return to full activity in July and August; non-reproductive females and immature Echidnas may not end hibernation until two months later. During euthermia, the body temperature can vary by 4 °C (39 °F) per day. The metabolic rate of the Echidna is around 30% of that of placental mammals, making it the lowest energy consuming mammal. This figure is similar to that of other animals that eat ants and termites; burrowing animals also tend to have low metabolism generally.
Questions have arisen as to why Echidnas hibernate, as it is seemingly unnecessary for survival; Echidnas begin their hibernation period while the weather is still warm, and food is generally always plentiful. One explanation of this phenomenon is that Echidnas want to be cautious with their energy reserves in order to maximize their foraging productivity. Another hypothesis is that Echidnas are descended from ectothermic ancestors but have taken to periodic endothermy for reproductive reasons, so that the young can develop more quickly. Supporters of this theory argue that males hibernate earlier than females because they finish their contribution to reproduction first, and they awake earlier to undergo spermatogenosis in preparation for mating, while females and young lag in their annual cycle. During the hibernation period, the animals stay in entirely covered shelter.
Short-beaked Echidnas can live anywhere that has a good supply of food. They locate food by smell, using sensors in the tip of their snout, and regularly feast on ants and termites. This view is based on the Echidna's method of shuffling around seemingly arbitrarily and using its snout in a probing manner. A study of Echidnas in New England has shown that they tend to dig up scarab beetle larvae in spring when the prey are active, but eschew this prey when it is inactive; this has been used to support the conjecture that Echidnas detect their prey using hearing. Vision is not believed to be significant in hunting, as blind animals have been observed to survive in the wild.
The Echidnas use their strong claws to pull apart nests and rotting logs to gain access to their prey. They are selective of what types of ants and termites they target because some of their would-be prey secrete repulsive liquids. They also have a preference for the eggs, pupae and winged phases of the insects. Echidnas hunt most vigorously towards the end of winter and early in spring, when their fat reserves have been depleted after hibernation and/or nursing. At this time of the year, ants have high body fat, and the Echidna targets their mounds. The animal also hunts beetles and earthworms, providing they are small enough to fit in a 5 mm gap. The proportion of ants and termites in the Echidna's diet depends to the availability of prey, and termites make up a larger part of its diet in drier areas where they are more plentiful. However, termites are preferred if available, as their bodies contain a smaller proportion of indigestible exoskeleton. Termites from the Rhinotermitidae family, however, are avoided due to their chemical defenses. Scarab beetle larvae are also a large part of the diet when and where available. In a study conducted in New England in New South Wales, 37% of the food intake consisted of beetle larvae, although the Echidna had to squash the prey in its snout as it ingested it, due to size.
Echidnas 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. They bend their belly together to shield the soft unprotected part, and can also urinate, giving off a pungent liquid, in an attempt to deter attackers. Male Echidnas also have a small spur on their rear legs that is believed to a defensive weapon that has since been lost to the evolutionary process. Echidnas typically try to avoid confrontation with predators due to their lack of anatomical weaponry. Instead, they use the colour of their spines, which is similar to the vegetation the dry Australian environment, to avoid detection. They have good hearing and tend to become stationary if sound is detected.
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 and the Kelp Welsh River, east of Port Moresby, in the east, where they may be found in open woodland.
Echidnas have the ability to swim, and have been seen cooling off in dams during high temperatures. They have also been seen crossing streams and also swimming for brief periods in seas off Kangaroo Island. They swim with only the snout above water, using it as a snorkel.
The solitary Short-beaked Echidna looks for a mate between May and September; the precise timing of the mating season varies with geographic location. In the months before the mating season, the size of the male's testes increases by a factor of three or more before spermatogenesis occurs. Both males and females give off a strong musky odour during the mating season, by turning their cloacas inside out and wiping them on the ground, secreting a glossly liquid believed to be an aphrodisiac. During courtship—observed for the first time in 1989—males locate and pursue females. Trains of up to ten males—often with the youngest and smallest male at the end of the queue—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. During this time, they forage for food together, and the train often changes composition as some males leave and other join the pursuit. 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. This process can take a few hours and the female can reject the suitor by rolling herself into a ball. After prodding and sniffing her back, the male is often observed to roll the female onto her side and then assume a similar position himself so that the two animals are abdomen to abdomen, having dug a small crater to lie in. They can lie with heads facing one another, or head to rear. If more than one male is in the vicinity there may be fighting over the female. Each side of the bilaterally symmetrical, rosette-like, four-headed penis [similar to that of reptiles and 7 centimetres (2.8 in) in length] is used alternately, with the other half being shut down between ejaculations. Sperm bundles of around 100 each appear to confer increased sperm motility, which may provide the potential for sperm competition between males. This process takes between half an hour and three. 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 after copulation, during which time the female constructs a nursery burrow. Following the gestation period, a single rubbery-skinned egg between 13 and 17 millimetres (0.5 and 0.7 in) in diameter and 1.5 and 2.0 grams (0.053 and 0.071 oz) in weight is laid from her cloaca directly into a small, backward-facing pouch that has developed on her abdomen. The egg is ovoid, leathery, soft and cream-coloured. Between laying and hatching, some females continue to forage for food while others dig a burrow and rest there until hatching. 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 centimetres (0.6 in) long and weigh between 0.3 and 0.4 gram (0.011 and 0.014 oz). After hatching, young Echidnas are known as puggles. Although newborns are still semitranslucent and still surrounded by the remains of the egg yolk, and the eyes are still barely developed, they already have well-defined front limbs and digits that allow it to climb on its mother's body. Hatchlings attach themselves to their mothers' milk areolae, specialised patches on the skin that secrete milk—monotremes lack nipples—through approximately 100–150 pores. The puggles were thought to have imbibed the milk by licking the mother's skin, but this has been superseded by a belief that it feeds by sucking the areola.
They have been observed ingesting large amounts during each feeding period, and mothers may leave them unattended in the burrow for between five and ten days in order to find food. Studies of captive Echidnas have shown that they can ingest milk once every two or three days and then increase their mass by 20% in one milk-drinking session lasting between one and two hours. Around 40% of the milk weight is converted into body mass, and as such a high proportion of milk is converted into growth, a correlation with the growth of the puggle and its mother's size has been observed. By the time the puggle is around 200 grams (7.1 oz) it is left in the burrow while the mother forages for food, and it reaches around 400 grams (14 oz) after around two months. 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. During this period, the young are left in a covered burrow while the mother forages, and the young are often predated. 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 after 180 to 205 days, usually in January or February, at which time they are around 800 and 1,300 grams (28 and 46 oz). There is no contact between the mother and young after this point.
The composition of the milk secreted by the mother changes over time. At the moment of birth, the solution is dilute and contains 1.25% fat, 7.85% protein, and 2.85% carbohydrates and minerals. Mature milk has much more concentrated nutrients, with 31, 12.4 and 2.8% of the aforementioned quantities respectively. Near weaning, the protein level continues to increase this is conjecture to be due to the need for keratin synthesis for hair and spines, to provide defences against the cold weather and predators.
The principal carbohydrate components of the milk are fucosyllactose and saialyllactose; it has a high iron content, which gives it a pink colour. The high iron content and low levels of free lactose contrasts with other eutherian mammals. Lactose production is believed to proceed along the same lines as in the platypus.
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 reaches sexual maturity between five and twelve 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, and the longest-lived echidna in captivity reached 49 years of age in a zoo in Philadelphia in the US. Echidnas contrast to other mammals in that their rates of reproduction and metabolism are lower, and they live longer, as though in slow motion, something caused at least in part by their low body temperature, which rarely exceeds 33o even when they are not hibernating.
Like its fellow monotreme the Platypus, the Short-beaked Echidna has a system of multiple sex chromosomes, in which males have four Y chromosomes and five X chromosomes. Male individuals appear to be X1Y1X2Y2X3Y3X4Y4X5 (figure), while females are X1X1X2X2X3X3X4X4X5X5. Weak identity between chromosomes results in meiotic pairing that yields only two possible genotypes of sperm, X1X2X3X4X5 or Y1Y2Y3Y4, thus preserving this complex system.
The Short-beaked Echidna is common throughout most of temperate Australia and lowland New Guinea, and is not listed as endangered. In Australia, the Echidna remains widespread across a wide range of conditions, including urban outskirts, coastal forests and dry inland areas. They are especially widespread in Tasmania and on Kangaroo Island.
The most common threats to the animal in Australia are motor vehicles and habitat destruction, which have led to localized extinctions. In Australia, the number of Short-beaked Echidnas has been less affected by land clearance than have some other species, since Short-beaked Echidnas do not require a specialized habitat beyond a good supply of ants and termites. As a result, they can survive in cleared land if the cut-down wood is left in the area, as the logs can be used as shelter and a source of insects. However, areas where the land has been completely cleared for single crops that can be mechanically harvested, such as wheatfields, have seen extinctions. Over a decade-long period, around one third of Echidna deaths reported to wildlife authorities in Victoria were due to motor vehicles, and the majority of wounded animals handed in were traffic accident victims. Studies have shown that Echidnas often choose to traverse drainage culverts under roads, so this is seen as a viable means of reducing deaths on busy roads in rural areas or national parks where the animals are more common.
Despite their spines, they are preyed on by birds, the Tasmanian Devil, dingoes, snakes, lizards, goannas, cats and foxes, although almost all victims are young. Goannas are known for their digging abilities and strong sense of smell and are believed to be have been the main predators of the Echidna before the introduction of most of the other predators by European settlers. Dingoes are known to kill Echidnas by rolling them over onto their backs and attacking their underbellies. A tracking study of a small number of Echidnas on Kangaroo Island concluded that goannas and cats were the main predators, although it has been speculated that foxes—absent in Kangaroo Island—would also be a major threat as the Echidna density in Tasmania—which is free from foxes—is higher in other parts of Australia.
They were eaten by indigenous Australians and the early European settlers of Australia. In contrast, hunting and eating of the Echidna in New Guinea has increased over time and caused a decline in the population and distribution areas; it is now believed to have disappeared from highland areas. The killing of Echidnas were a taboo in traditional culture, but since the tribespeople have become increasingly Christianised by western missionaries, hunting has increased, and the animals have been more easily tracked down due to the use of dogs.
Infection with the introduced parasite Spirometra erinaceieuropaei is considered fatal for the Echidna. This is a waterborne infection contracted through sharing drinking areas with infected dogs, foxes, cats and dingos, which do not die from the parasite. The infection is seen as being more dangerous in drier areas where more animals are sharing less bodies of water, increasing the chance of transmission. The Wildlife Preservation Society of Queensland runs an Australia-wide survey called Echidna Watch to monitor the species in Australia. Echidnas are also known to be affected by tapeworms, protozoal and herpes-like viral infections, but there is little knowledge of how it affects the health of the animals or the populations.
Although it considered easy to keep Echidnas healthy in captivity, breeding is difficult, partly due to the relatively infrequent cycle. In 2009, Perth Zoo managed to breed some captive Short-beaked Echidnas. Up until 2006, only five zoos have managed to breed a captive Short-beaked Echidna, but no captive-bred young have survived to maturity. Of these five institutions, only one in Australia—Sydney's Taronga Zoo—managed to breed echidnas, in 1977. The other four cases occurred in the northern hemisphere, two in the United States and the others in western Europe. In these cases, breeding occurred six months out of phase compared to Australia after the animals had adapted to northern hemisphere seasons. The failure of captive breeding programs 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. 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 for its own defence and turned into an Echidna. Another story tells of a greedy man who kept food from his tribe; warriors speared him and he crawled away into the bushes, where he turned into an Echidna, the spears becoming his spines.
The Short-beaked Echidna is an iconic animal in contemporary Australia, notably appearing 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, when it was on the 25-cent stamp; it appeared on a 37-cent stamp in 1987, and in 1992 it was on the 35-cent stamp. The anthropomorphic echidna Millie was a mascot for the 2000 Summer Olympics. Knuckles the Echidna from the Sonic the Hedgehog series is also based on the short beaked Echidna.
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