Tasmanian Devil (Sarcophilus harrisi) is
Australia's largest living carnivorous marsupial (previously it
was the thylacine ,or Tasmanian Tiger, now presumed extinct) and,
since it's extinction from the mainland at least 600 years ago,
it is found exclusively on the island state of Tasmania. Since
1941 it has been a protected species but a (presumed) new and
contagious disease is threatening the population's long term viability
Length 550-650mm (f-m), weight 7-9kg (f-m), life span 6 years in the wild, longer in captivity.
The scientific name means Harris's meat lover, named after the naturalist George Harris who wrote the first published description of the Tasmanian Devil in 1807. The name has subsequently been changed to S. laniarius but the original name is still widely used. It is most closely related to quolls.
It has the appearance of a medium sized dog, but more stocky and muscular, with a large head, brownish-black fur with irregular white patches on the chest and rump and a thick tail. In common with many marsupials it stores fat in its tail and an unhealthy devil can often be identified by a thin tail.
Devils have long whiskers on the face and on the top of the head. These help when foraging for prey in the dark and provide spatial information about the location of other devils when group feeding, thus helping to avoid disputes. If agitated the devil is capable of producing a very strong odour, said to rival the skunk.
The dominant senses are hearing and smell. Sight is relatively poor and, in common with most nocturnal hunters, is black and white. This vision is particularly suited for seeing movement, and any prey that stands still is unlikely to be detected by sight alone.
Devil bite force is especially strong, roughly equal to a dog four times its weight. This is similar to hyenas. Devils yawn often - something which is in part a redirection of nervous energy to something that's harmless. Devil ears flush with blood when agitated or excited and this, coupled with the lack of any hair on the ears gives them a striking appearance. Some believe this appearance was part of the reason for the name 'devil' but the main reason is probably because of the awful screeching sound made at nighttime which would undoubtedly have frightened the God-fearing Christian settlers.
Female sexual maturity is reached in their second year,and breeding will take place once a year for the next three years (occasionally four years). Mating takes place in February/March and is quite a violent affair. The female will have developed extra fat at the back of the neck so as to give extra protection from the males bite. The male will subdue the female and then keep her protected from other males . There is much fighting between males over the female and scars and damaged ears and noses are visible on most older devils.
Gestation lasts for 25-31 days, whereafter the female will produce 20-30 young. However, she only has 4 teats so the remainder will die soon after birth. At birth the devils weigh 0.2 grammes and are hairless, blind and deaf. They crawl to the rear facing pouch and attach to a nipple where they remain and develop for the next 100 days. After leaving the pouch they will not return to it but will stay in the den for five months, leaving the den around Christmas time - the time when most wallaby joeys are first appearing.
Ecology and behaviour
Devils are nocturnal and crepuscular but also like to 'sunbathe' . They are found right across the island including the outskirts of urban areas and are fairly common (see DFTD below). When young they are good climbers and are good swimmers throughout their lives. They are strong runners although the fact that the front legs are longer than the hind legs gives them an ungainly appearance. The do not form packs and are not strictly territorial, although they will defend the small area around them as they move through their territory. Females defend the area around the den.
Tasmanian Devils will eat any meat that is available. They are predominantly carrion eaters but will take live prey as large as an adult wombat - supposedly their favoured food. What they eat normally depends on what is available and thus they will take platypus, echidnas, wallabies, fish, stock (generally only if injured or dead) etc, even eating prey as small as insects.
On a large kill they will eat voraciously and can consume 40% of their body weight in 30 minutes (this is typical for predators). However, they need to eat 15% of their body weight each day so this amount is only sufficient for a dew days.
Their powerful jaws enable them to crush bones and teeth and so no trace of the dead animal remains. This is a benefit to farmers as it prevents the spread of insects/mites that might otherwise attack livestock.
Devil facial tumour disease (DFTD)
DFTD causes tumours to form in and around the mouth and sometimes elsewhere in the body, interfering with feeding and leading to death by starvation approximately 5 months after the lumps are first noticed. The disease was first noticed in 1996 and since then over 75 % of the state has become affected, with estimates of the population impact varying from 50 to60%, with up to 95% gone from some areas (in high density populations), with adult devils suffering more than juveniles. The spread of the disease has been from the east, coinciding with the most cleared area of the island.
It is now known that the cause of the disease is an infectious cancer, one of only two types ever discovered, with the diseased cells being transfered by direct contact during mating. The research also indicates that the infective agent is a rogue cell line of unknown origin.Tasmanian devils are so genetically similar that the Devils' immune system is not triggered by the cancer. No tests are currently available for DFTD. A programme of transplanting disease-free animals to the mainland to set-up a security breeding population is underway.
2005 a recommendation was made to include the devil on the Tasmanian
Threatened Species list as a vulnerable species, which means that
it is at risk of extinction in the "medium term". This
was subsequently agreed to and there is now a call to up-rate this
to endangered due to the population loss now having reached 50%.
The decline in devil numbers is also seen as an ecological problem, since its presence in the Tasmanian forest ecosystem is believed to have prevented the establishment of the Red Fox, illegally introduced to Tasmania in 2001. Foxes are a problematic invasive species in all other Australian States, and the establishment of foxes in Tasmania would hinder the recovery of the Tasmanian Devil.
The further spread of the disease and the subsequent extinction of the animal in the wild now seems inevitable.
For the latest information on the disease and how you can help, go to www.tassiedevil.com.au
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