Short-beaked echidna

The short-beaked echidna was first described by George Shaw in 1792. He named the species Myrmecophaga aculeata, thinking that it might be related to the giant 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 comes from Ancient Greek (), meaning "fast", and (), meaning "tongue", and aculeatus means 'spiny' or 'equipped with spines' in Latin. 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 echidnas, are all significantly larger than T. aculeatus, and their diets consist 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. The five subspecies of the short-beaked echidna are each found in different geographical locations. 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 the arid parts of Australia, including the Northern Territory. • T. a. multiaculeatus is found on Kangaroo Island. 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 66 million years ago, between the Cretaceous and Tertiary periods. , Tasmania The short-beaked echidna was commonly called the spiny anteater in older books, though this term has fallen out of fashion since the echidna is only very distantly related 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 . In Central Australia southwest of Alice Springs, the Pitjantjatjara term is or , from the word for spike of porcupine grass (Triodia irritans). The word can also mean 'slowpoke'. In the Wiradjuri language of Central NSW, it is called . In the central Cape York Peninsula, it is called in Pakanh, where is a qualifier meaning 'meat' or 'animal', in Uw Oykangand and in Uw Olkola, where is a qualifier meaning 'meat' or 'animal'. In the highland regions of southwestern New Guinea, it is known as the in the Daribi and Chimbu languages. ==Description==

Short-beaked echidnas are typically in length, with of snout, and weigh between . 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. The earholes are on either side of the head, with no external pinnae. The nostrils and the mouth are at the distal end of the snout; the mouth cannot open wider than . 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 long, are 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 underside and short tail are also covered in fur. The power of the limbs is based on strong musculature, particularly around the shoulder and torso areas. The mechanical advantage of its arm is greater than that of humans, as its biceps connects the shoulder to the forearm at a point further down than for humans, and the chunky humerus allows more muscle to form. The claws on the hind feet are elongated and curved backward to enable cleaning and grooming between the spines. Like the platypus, the echidna has a low body temperature—between —but, unlike the platypus, which shows no evidence of torpor or hibernation, the body temperature of the echidna may fall as low as . The echidna does not pant or sweat and normally seeks shelter in hot conditions. Despite their inability to sweat, echidnas 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 occurs in this manner, while most of the rest is through the skin and respiratory system. Most of this is replenished by its substantial eating of termites—one laboratory study reported ingestion of around a day, most of which was water. This can be supplemented by drinking water, if available, or licking morning dew from flora. In the Australian autumn and winter, the echidna enters periods of torpor or deep hibernation. Because of its low body temperature, it becomes sluggish in very hot and very cold weather. the cloaca, for the passage of faeces, urine and reproductive products. which is nearly a quarter of his body length when erect. The gestating female develops a pouch on her underside, where she raises her young. The musculature of the short-beaked echidna has a number of unusual aspects. The panniculus carnosus, an enormous muscle just beneath the skin, 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 vertebra, for the echidna it occurs at the seventh thoracic vertebra. The shorter spinal cord is thought to allow flexibility to enable wrapping into a ball. The musculature of the face, jaw and tongue is specialised for feeding. The tongue is the animal's sole means of catching prey, and can protrude up to outside the snout. The tongue is sticky because of the presence of glycoprotein-rich mucus, which both lubricates movement in and out of the snout and helps to catch ants and termites, which adhere to it. The tongue is protruded 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 a rapid flow of blood, which allows 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. This is partly achieved through the elasticity of the tongue and the conversion of elastic potential energy into kinetic energy. The tongue also has an ability to avoid picking up splinters while foraging in logs; the factors behind this ability are unknown. It can eat quickly; a specimen of around can ingest of termites in 10 minutes. Numerous physiological adaptations aid the lifestyle of the short-beaked echidna. Because the animal burrows, it must 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, which 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 organs to such a shortage; laboratory testing has revealed 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 sclera of the eyeball is similar to that of reptiles and avians. The echidna has the flattest lens of any animal, giving it the longest focal length. This similarity to primates and humans allows 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; the whole eye is believed to distort, so the distance between the lens and retina 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 ears are sensitive to low-frequency sound, which may be ideal for detecting sounds emitted by termites and ants underground. The macula of the ear is very large compared to other animals, and is used as a gravity sensor to orient the echidna. The large size may be important for burrowing downwards. 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, which also has mucous glands on the end that act as electroreceptors. Echidnas can detect electric fields of 1.8mV/cm—1000 times more sensitive than humans—and dig up buried batteries. A series of push rods protrude from the snout. These are columns of flattened, spinous cells, with roughly an average diameter of and a length of . The number of push rods per square millimetre of skin is estimated to be 30 to 40. Longitudinal waves are believed to be picked up and transmitted through the rods, acting as mechanical sensors, to allow prey detection. A well-developed olfactory system may be used to detect mates and prey. A highly sensitive optic nerve has been shown to have visual discrimination and spatial memory comparable to those of a rat. The brain and central nervous system have been extensively studied for evolutionary comparison with placental mammals, particularly with its fellow monotreme, the platypus. The average brain volume is , similar to a cat of approximately the same size; while the platypus has a largely 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, and the brain cells are larger and more densely packed and organised in the echidna than the platypus, suggesting 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 large 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 volume in comparison to 29% for humans. This part of the brain in humans is thought 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 opening a trap door to access food, and the echidna's ability to remember what it has learnt for over a month, has led scientists to conclude 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 , and this effect is suppressed at other temperatures. ==Ecology and behaviour==

building a defensive burrow No systematic study of the ecology of the short-beaked echidna has been published, but studies of several aspects of their ecological behaviour have been conducted. They 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 they defend against other echidnas, but range over a wide area. 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 patterns of activity, becoming crepuscular or nocturnal. 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 periods during the Australian winter when it hibernates, both in cold regions and in regions with more temperate climates. During hibernation, the body temperature drops to as low as . The heart rate falls to four to seven beats per minute—down from 50 to 68 at rest Echidnas begin to prepare for hibernation 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. burrowing animals also tend to have low metabolism generally. Echidnas hibernate even though it is seemingly unnecessary for survival; they begin their hibernation period while the weather is still warm, and food is generally always plentiful. One explanation is that echidnas maximize their foraging productivity by exercising caution with their energy reserves. Another hypothesis is that they are descended from ectothermic ancestors, but have taken to periodic endothermy for reproductive reasons, so that the young can develop more quickly. , Canberra. Short-beaked echidnas can live anywhere with a good supply of food, and regularly feast on ants and termites. They are believed to locate food by smell, using sensors in the tips of their snouts, by shuffling around seemingly arbitrarily, and using their snout in a probing manner. Vision is not believed to be significant in hunting, as blind animals have been observed to survive in the wild. They avoid ants and termites that secrete repulsive liquids, and have a preference for the eggs, pupae and winged phases of the insects. Echidnas hunt most vigorously towards the end of the southern winter and early in spring, when their fat reserves have been depleted after hibernation and nursing. At this time, ants have high body fat, and the echidna targets their mounds. However, termites are preferred, if available, as their bodies contain a smaller proportion of indigestible exoskeleton. Termites from the Rhinotermitidae family are avoided due to their chemical defences. Scarab beetle larvae are also a large part of the diet when and where available. In the New England study, 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. This is based on the estimation that a single echidna will move up to of soil a year, that it is the most widespread of any terrestrial Australian species, is relatively common, and that other bioturbators have been heavily impacted by human settlement. Reproduction The solitary short-beaked echidna looks for a mate between May and September; 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 glossy liquid believed to be an aphrodisiac. During this time, they forage for food together, and the train often changes composition, as some males leave and others 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. If more than one male is in the vicinity, fighting over the female may occur. This process takes between a half and three hours. Fertilisation occurs in the oviduct. Gestation takes between 21 and 28 days after copulation, 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 burrows and rest there until hatching. Hatchlings are about long and weigh between . 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 them to climb on their mothers' bodies. Studies of captives have shown 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. 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 31.0, 12.4 and 2.8% of the aforementioned nutrients, respectively. 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 differ from eutherian mammals. Lactose production is believed to proceed along the same lines as in the platypus. The longest-lived specimen reached 49 years of age in a zoo in Philadelphia. In contrast to other mammals, echidna rates of reproduction and metabolism are lower, and they live longer, as though in slow motion, Homosexual behaviours between males have been observed in captivity; this has sometimes led to cloacal injuries being observed following the interactions. ==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, it remains widespread across a wide range of habitats, including urban outskirts, coastal forests and dry inland areas, and is especially widespread in Tasmania and on Kangaroo Island. In Australia, the number of short-beaked echidnas has been less affected by land clearance than have some other species, since they do not require a specialised habitat beyond a good supply of ants and termites. although almost all victims are young. Goannas are known for their digging abilities and strong sense of smell, and are believed to have been the main predators of the echidna before the introduction of eutherian mammals. Infection with the introduced parasitic tapeworm Spirometra erinaceieuropaei is considered fatal for the echidna. This waterborne infection is 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 fewer 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. Echidnas are also known to be affected by other tapeworms, protozoans and herpes-like viral infections, but little is known of how the infections affect the health of the animals or the populations. Although it is 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, and in 2015 the first zoo-born echidnas were successfully bred there. Until 2006, only five zoos have managed to breed short-beaked echidnas, 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. ==Cultural references==

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 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. The fictional character Knuckles the Echidna from Sonic the Hedgehog is a red short-beaked echidna who possesses superhuman strength. The short-beaked echidna is an iconic animal in contemporary Australia, notably appearing on the five-cent coin (the smallest denomination), and on a $200 commemorative coin released in 1992. The anthropomorphic echidna Millie was a mascot for the 2000 Summer Olympics. ==See also==