The
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.
Scientific name
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.
Physical description
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.
Reproduction
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.
In May
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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