Australian Marsupials - The Tasmanian Devil
Endangered Marsupials
The Tassie Devil
The Tasmanian devil (Sarcophilus harrisii) is another of Australia's marsupials. Marsupials are pouched animals whose young are born in a very immature state. The 'joeys' are about the size of a jellybean and claw their way to the pouch unaided, despite being blind and naked. Once in the pouch they attach themselves to a teat and continue their development.
The Tasmanian devil has a few features which make it easily differentiated from other animals. The 'devil' part of the name comes from its demonic howling and screeching, its bad temper, its fierce demeanour and its pungent odour when stressed. Communal feeding takes place with great ferocity.
The head and shoulders are disproportionately large. It is always black.
The devil once had a very bad reputation with early settlers as a killer of domestic livestock. For over a century it was trapped, poisoned and shot. They became increasingly rare until, in June 1941, legislation was introduced to protect them. Nowadays the belief is that it is more of a scavenger than a killer.
With the extinction of the thylacine in 1936, the Tasmanian devil became the world's largest carnivorous marsupial. As might be supposed, the Tasmanian devil is endemic to Tasmania, the island state situated some 300 kilometres south of the mainland, Australia.
Description
The thickset Tasmanian devil is about the size of a stocky but small dog. The broad head, neck and forequarters are muscular and disproportionately large for the rest of the body, especially in the male. The massive head and chest makes up 40% of the weight of the 8 to 12 kg male, which may stand 30cm high at the shoulder. Females weigh between 6 and 7 kg. The jaws are very powerful, giving the devil one of the most powerful bites, for its size, of any mammal. The jaws can open to 75 to 80o, giving them sufficient power to bite through thick metal wire. It has 42 teeth, which grow continuously. The devil's hearing is its strongest sense. It also has a keen nose and can pick up smells up to a kilometre away.
Fat is stored in the short, thick tail which acts as a counterbalance when the animal is moving at speed. There is an ano-genital scent gland at the base of the tail. The pelage is jet black with white markings on the flank and at the base of the tail. There is often a white bar across the chest. The white markings are unique to each animal, helping animals identify each other and improving camouflage. Roughly 5% of devils are totally black.
The forelegs have five digits. The claws are short and sharp to facilitate digging and holding prey. Partial webbing between the first and second knuckle aids in digging and swimming. Devils are powerful swimmers, paddling with the forelegs and letting the hindquarters trail behind. The hind legs are shorter and equipped with four digits.
Habitat
The densest populations of devils were found in northern, eastern and central Tasmania in a variety of habitats including coastal heath, forest, woodland and agricultural areas. If they can find shelter and refuge during the day and food at night, they will live almost anywhere. Some live in uninhabited dwellings or outhouses and have been known to steal blankets and clothing to line their dens.
Breeding
Reproduction, as stated by one source, is very 'robust and competitive'. Males fight for females then guard them jealously. During the breeding season (around March), females may ovulate three times in three weeks. There is no embryonic diapause. Gestation takes three weeks. There are only four nipples in the backward-facing pouch so many newborns do not survive. Two or three is the norm.
Once the young make contact with a nipple, the nipple swells and becomes firmly clamped inside the newborn. This prevents the tiny joey from falling out. Weaning takes place at 5 to 6 months and the young will wait in a den while the mother goes off to hunt. The young are living on their own in the bush by late December. Lifespan in the wild is believed to be 7 to 8 years.
Diet
The devil feeds on whatever is available and scavenges for a lot of its food. It cleans up roadkill with gusto often becoming roadkill itself in the process. The jaws and teeth are so powerful that an entire carcase will be consumed including bones, fur and everything else. This total consumption of a carcase reduces the spread of insects such as blowflies.
Wallabies, birds, reptiles, amphibians, dead cattle and sheep are all sources of food as are potoroos, bettongs and other small mammals. Because of the strength of its jaws and the sharp teeth, it finds wombats at easy prey and the high fat content is an added incentive. Feeding is a rowdy, communal affair with much screeching and scrapping as the animals establish their dominance. Quolls will often attempt to share the quarry of the devil.
If the opportunity arises, devils can eat up to 40% of their bodyweight in half an hour. They then waddle away and lie down to digest their meal.
Behaviour
The devil will move up to 16km daily over well-defined trails. The animals are not territorial although they do have home ranges. The devil is able to regulate its body temperature with relative ease and can be active during the day without distress.
Mostly devils amble at a slowish speed but they can gallop along if need be. The gait appears ungainly as the forelegs move independently but the hind legs move as one. This gives the devil great stamina and they are capable of maintaining good speeds for considerable distances. Young devils will climb trees until they become too weighty.
The wide gape or yawn looks very threatening but it is believed to be performed more from fear and uncertainty than from aggression. When under stress, they have a pungent odour. Vocalisations vary from harsh coughs and snarls to screeching and a sharp sneeze which is the prequel to a fight. Many of these behaviours are part of a ritual to minimise otherwise harmful fighting. However many devils bear scars from fighting at food sites.
Until a decade or two ago, threats to the Tasmanian devil included food availability, competition from others animals including quolls and foxes, persecution, loss of habitat and being killed on the roads. However a bigger threat is Devil Facial Tumour Disease (DFTD). This is a transmissible cancer first noticed among devils in the mid 1990s. It is now decimating the devil population. This debilitating cancer takes the form of ulcerated tumours around the jaws and head. The disease is found in around 50% of wild devils and generally results in death within three to five months.
Because of export restrictions and the lack of success breeding devils overseas, there are relatively few Tasmanian devils outside of Australia.
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