The Tasmanian devil



The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae. It was once native to mainland Australia and is now found in the wild only on the island state of Tasmania, including tiny east-coast Maria Island where there is a conservation project with disease-free animals.

The size of a small dog, the Tasmanian devil became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936. It is related to quolls and distantly related to the thylacine. It is characterised by its stocky and muscular build, black fur, pungent odour, extremely loud and disturbing screech, keen sense of smell, and ferocity when feeding. The Tasmanian devil's large head and neck allow it to generate among the strongest bites per unit body mass of any extant mammal land predator, and it hunts prey and scavenges carrion as well as eating household products if humans are living nearby.

Although it usually is solitary, it sometimes eats with other devils and defecates in a communal location. Unlike most other dasyurids, the devil thermoregulates effectively and is active during the middle of the day without overheating. Despite its rotund appearance, the devil is capable of surprising speed and endurance, and can climb trees and swim across rivers.

The tasmanian devil, the size of a small dog, the largest carnivorous marsupial in the worldIt is believed that ancient marsupials migrated from what is now South America to Australia tens of millions of years ago during the time of Gondwana, and that they evolved as Australia became more arid. Fossils of species similar to modern devils have been found, but it is not known whether they were ancestors of the contemporary species, or whether the current devils co-existed with these species. The date that the Tasmanian devil became locally extinct from the Australian mainland is unclear; most evidence suggests they had contracted to three relict populations around 3000 years ago. A tooth found in Augusta, Western Australia has been dated to 430 years ago, but archaeologist Oliver Brown disputes this and considers the devil's mainland extinction to have occurred around 3000 years ago.

This disappearance is usually blamed on dingoes, which are absent from Tasmania. Because they were seen as a threat to livestock and animals that humans hunted for fur in Tasmania, devils were hunted and became endangered. In 1941, the devils, which were originally seen as implacably vicious, became officially protected. Since then, scientists have contended that earlier concerns that the devils were the most significant threat to livestock were overestimated and misplaced.

Devils are not monogamous, and their reproductive process is very robust and competitive. Males fight one another for the females, and then guard their partners to prevent female infidelity. Females can ovulate three times in as many weeks during the mating season, and 80% of two-year-old females are seen to be pregnant during the annual mating season. Females average four breeding seasons in their life and give birth to 20–30 live young after three weeks' gestation. The newborn are pink, lack fur, have indistinct facial features and weigh around 0.20 g (0.0071 oz) at birth. As there are only four nipples in the pouch, competition is fierce and few newborns survive. The young grow rapidly and are ejected from the pouch after around 100 days, weighing roughly 200 g (7.1 oz). The young become independent after around nine months, so the female spends most of her year in activities related to birth and rearing.

Since the late 1990s, the devil facial tumour disease (DFTD) has drastically reduced the devil population and now threatens the survival of the species, which in 2008 was declared to be endangered. Programs are currently being undertaken by the Government of Tasmania to reduce the impact of the disease, including an initiative to build up a group of healthy devils in captivity, isolated from the disease. While the thylacine was extant it preyed on the devil, which targeted young and unattended thylacine cubs in their dens. Localised populations of devils have also been severely reduced by collisions with motor vehicles, particularly when they are eating roadkill.

The devil is an iconic symbol of Tasmania and many organisations, groups and products associated with the state use the animal in their logos. It is seen as an important attractor of tourists to Tasmania and has come to worldwide attention through the Looney Tunes character of the same name. Starting in 2013, Tasmanian devils are again being sent to zoos around the world as part of the Australian government's Save the Tasmanian Devil Program.

Devils are found in all habitats on the island of Tasmania, including the outskirts of urban areas, and are distributed throughout the Tasmanian mainland and on Robbins Island (which is connected to mainland Tasmania at low tide). The north-western population is located west of the Forth River and as far south as Macquarie Heads. Previously, they were present on Bruny Island from the 19th century, but there have been no records of them after 1900, and they were introduced to Badger Island in the mid-1990s but are thought to have died out by 2005. A study has modelled the reintroduction of DFTD-free Tasmanian devils to the mainland in areas where dingoes are sparse. It is proposed that devils would have fewer impacts on both livestock and native fauna than dingoes, and that the mainland population could act as an additional insurance population. In September 2015, 20 immunised captive-bred devils were released into Narawntapu National Park, Tasmania. Two later died from being hit by cars.

The "core habitat" of the devils is considered to be within the "low to moderate annual rainfall zone of eastern and north-western Tasmania". Tasmanian devils particularly like dry sclerophyll forests and coastal woodlands. Although they are not found at the highest altitudes of Tasmania, and their population density is low in the button grass plains in the south-west of the state, their population is high in dry or mixed sclerophyll forests and coastal heaths. Devils prefer open forest to tall forest, and dry rather than wet forests. They are also found near roads where roadkill is prevalent, although the devils themselves are often killed by vehicles while retrieving the carrion. According to the Threatened Species Scientific Committee, their versatility means that habitat modification from destruction is not seen as a major threat to the species.

The devil is directly linked to the Dasyurotaenia robusta, a tapeworm which is classified as Rare under the Tasmanian Threatened Species Protection Act 1995. This tapeworm is found only in devils.

Females start to breed when they reach sexual maturity, typically in their second year. At this point, they become fertile once a year, producing multiple ova while in heat. As prey is most abundant in spring and early summer, the devil's reproductive cycle starts in March or April so that the end of the weaning period coincides with the maximisation of food supplies in the wild for the newly roaming young devils. Occurring in March, mating takes places in sheltered locations during both day and night. Males fight over females in the breeding season, and female devils will mate with the dominant male. Females can ovulate up to three times in a 21-day period, and copulation can take five days; one instance of a couple being in the mating den for eight days has been recorded. Devils are not monogamous, and females will mate with several males if not guarded after mating; males also reproduce with several females during a season. Females have been shown to be selective in an attempt to ensure the best genetic offspring, for example, fighting off the advances of smaller males. Males often keep their mates in custody in the den, or take them along if they need to drink, lest they engage in infidelity. Males can produce up to 16 offspring over their lifetime, while females average four mating seasons and 12 offspring. Theoretically this means that a devil population can double on an annual basis and make the species insulated against high mortality. The pregnancy rate is high; 80% of two-year-old females were observed with newborns in their pouches during the mating season. More recent studies of breeding place the mating season between February and June, as opposed to between February and March.

Gestation lasts 21 days, and devils give birth to 20–30 young standing up, each weighing approximately 0.18–0.24 grams (0.0063–0.0085 oz). At birth, the front limb has well-developed digits with claws; unlike many marsupials, the claws of baby devils are not deciduous. As with most other marsupials, the forelimb is longer (0.26–0.43 cm or 0.10–0.17 in) than the rear limb (0.20–0.28 cm or 0.079–0.110 in), the eyes are spots, and the body is pink. There are no external ears or openings. Unusually, the gender can be determined at birth, with an external scrotum present.

Tasmanian devil young are variously called "pups", "joeys", or "imps".[106] When the young are born, competition is fierce as they move from the vagina in a sticky flow of mucus to the pouch. Once inside the pouch, they each remain attached to a nipple for the next 100 days. The female Tasmanian devil's pouch, like that of the wombat, opens to the rear, so it is physically difficult for the female to interact with young inside the pouch. Despite the large litter at birth, the female has only four nipples, so there are never more than four babies nursing in the pouch, and the older a female devil gets, the smaller her litters will become. Once the young have made contact with the nipple, it expands, resulting in the oversized nipple being firmly clamped inside the newborn and ensuring that the newborn does not fall out of the pouch. On average, more females survive than males, and up to 60% of young do not survive to maturity.

Milk replacements are often used for devils that have been bred in captivity, for orphaned devils or young who are born to diseased mothers. Little is known about the composition of the devil's milk compared to other marsupials.

Inside the pouch, the nourished young develop quickly. In the second week, the rhinarium becomes distinctive and heavily pigmented.[101] At 15 days, the external parts of the ear are visible, although these are attached to the head and do not open out until the devil is around 10 weeks old. The ear begins blackening after around 40 days, when it is less than 1 cm (0.39 in) long, and by the time the ear becomes erect, it is between 1.2 and 1.6 cm (0.47 and 0.63 in). Eyelids are apparent at 16 days, whiskers at 17 days, and the lips at 20 days. The devils can make squeaking noises after eight weeks, and after around 10–11 weeks, the lips can open. Despite the formation of eyelids, they do not open for three months, although eyelashes form at around 50 days. The young—up to this point they are pink—start to grow fur at 49 days and have a full coat by 90 days. The fur growing process starts at the snout and proceeds back through the body, although the tail attains fur before the rump, which is the last part of the body to become covered. Just before the start of the furring process, the colour of the bare devil's skin will darken and become black or dark grey in the tail.

The devils have a complete set of facial vibrissae and ulnar carpels, although it is devoid of anconeal vibrissae. During the third week, the mystacials and ulnarcarpals are the first to form. Subsequently, the infraorbital, interramal, supraorbital and submental vibrissae form. The last four typically occur between the 26th and 39th day.
Their eyes open shortly after their fur coat develops—between 87 and 93 days—and their mouths can relax their hold of the nipple at 100 days. They leave the pouch 105 days after birth, appearing as small copies of the parent and weighing around 200 grams (7.1 oz). Zoologist Eric Guiler recorded its size at this time as follows: a crown-snout length of 5.87 cm (2.31 in), tail length of 5.78 cm (2.28 in), pes length 2.94 cm (1.16 in), manus 2.30 cm (0.91 in), shank 4.16 cm (1.64 in), forearm 4.34 cm (1.71 in) and crown-rump length is 11.9 cm (4.7 in). During this period, the devils lengthen at a roughly linear rate.

After being ejected, the devils stay outside the pouch, but they remain in the den for around another three months, first venturing outside the den between October and December before becoming independent in January. During this transitional phase out of the pouch, the young devils are relatively safe from predation as they are generally accompanied. When the mother is hunting they can stay inside a shelter or come along, often riding on their mother's back. During this time they continue to drink their mother's milk. Female devils are occupied with raising their young for all but approximately six weeks of the year. The milk contains a higher amount of iron than the milk of placental mammals. In Guiler's 1970 study, no females died while rearing their offspring in the pouch. After leaving the pouch, the devils grow by around 0.5 kg (1.1 lb) a month until they are six months old. While most pups will survive to be weaned, Guiler reported that up to three fifths of devils do not reach maturity. As juveniles are more crepuscular than adults, their appearance in the open during summer gives the impression to humans of a population boom. A study into the success of translocated devils that were orphaned and raised in captivity found that young devils who had consistently engaged with new experiences while they were in captivity survived better than young who had not.

Embryonic diapause does not occur.

Guiler has reported that consecutive hermaphroditism (sex change) has occurred in captured devils, while Pemberton and Mooney recorded in 2004 the case of an animal with a scrotum and a non-functional pouch.

In an apparent response to reduced competition caused by devil facial tumour disease, female devils in regions with the disease are now more likely to begin breeding at the age of one year. The disease has also led to the reproductive season being less well-defined, with births more spread out throughout the year. Litters born to mothers with DFTD have more female pups than male pups.

A slow-release hormonal contraceptive implant for female devils is being developed and tested in a joint program between the Save the Tasmanian Devil program, the Zoo and Aquarium Association, the Taronga Conservation Society and the University of Sydney. This wildlife contraceptive program is aimed to help the devils continue with their wild behaviour by mating freely, but without certain females contributing too much to the next generation, which "can have long-term genetic consequences for the insurance population". Contraceptive trials in male devils showed that their testosterone increased, instead of decreasing as other male mammals' testosterone does. Early studies suggest that the female contraception has been successful, and the female contraceptive implants will be tested in the Maria Island insurance population.

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