devil facts

Tasmanian Devil - Sarcophilus harrisii

Taxonomy

Kingdom: Animalia (The animals)
Phylum: Chordata (Animals with back bones)
Class: Mammalia (Animals with fur and mammary glands)
Subclass: Marsupialia (Mammals with marsupiums or pouches)
Order: Polyprotodonta (Many front teeth)
Super Family: Dasyuromorphia (Marsupial carnivores)
Family: Dasyuridae ('Spiky Tails')
Genus: Sarcophilus ('Flesh Lover')
Species: harrisii (After Lt George Harris the general surveyor for the Colony)
Sarcophilus harrisii: (Boitard, 1841) Boitard was a naturalist who first suggested this classification in 1841

The family Dasyuridae comprises of several genus including Sarcophilus and Dasyurus. The only member of Sarcophilus in modern times is the Tasmanian devil (Sarcophilus harrisii). Dasyurus in Tasmania has two representative species the Eastern quoll (Dasyurus viverinus) and the Spotted-tail quoll (Dasyurus maculatus). Because of this evolutionary divergence at the family level it suggests that the quolls and the devil are the closest living relatives of each other.

Other animals in Tasmania that belong to the family Dasyuridae but are less closely related to Tasmanian devils include the Dusky Antechinus (Antechinus swainsonii), the Swamp Antechinus (Antechinus minimus) and the White-footed dunnart (Sminthopsis leucopus). The extinct Thylacine or Tasmanian tiger (Thylacinus cyanocephalus) is also a distant relative of the devil belonging to the same order.

No subspecific variations of Sarcophilus harrisii are known to exist. Recent studies by Dr Menna Jones suggest that there is a slight East to West genetic variation in Tasmanian devils which may be contributing to the current spread of DFTD (Devil Facial Tumour Disease) in the more densely populated Eastern genetic group.

Nomenclature

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Devils were described very early in Tasmanian colonial history. Tasmania was colonised in 1803 by England for the use as a penal settlement. Lt George Harris, the general surveyor for the Van Diemen's Land Colony (later to be called Tasmania) and amateur naturalist described a new species of Didelphid, the Tasmanian devil to the prestigious Linnaean Society in London as Didelphis ursina in 1807. Didelphis ursina translates loosely to 'possum bear'. Another scientist Thomas pointed out in 1903 that this was the same name given to common wombat by Shaw in 1800 so was not available for devils. Thomas suggested the name Sarcophilus satanicus (Satan's flesh eater).


In 1807 Lt Harris in his description, stated that the animal was known by the 'vulgar name of native devil'. It was therefore ingrained into the European settler's very early that this was an animal to fear. The name devil is believed to have come from the ferocious sound that the devil makes.

Devils are also very secretive and elusive making it very difficult to observe a devil. It is therefore very easy to identify the source of the sound but not its location. It was most likely that stories circulated about 'a devil of an animal' or belief that something in the bush was demonic or satanic. The bright red pointy ears and the huge gape that a devil has do not help its 'otherworldly' image!

In 1912 Thomas noted that Boitard, a French naturalist had suggested Sarcophilus harrisii in 1841 which predated and was more accurate than other classifications. This nomenclature has been used for the modern devil since.
In 2004 a move was made to reclassify the devil as Sarcophilus laniarius but its use was rejected by the scientific community and it remains Sarcophilus harrisii.

Evolution

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Fossil evidence of devils indicates that they were found right across Australia in the Pleistocene and Holocene and are described as two species. Sarcophilus laniarius dawsoni is smaller than the current species and Sarcophilus laniarius is much larger than current and were first described in 1838.

Sarcophilus laniarius was around 15 -16% larger than the current species therefore approximately 50% more body mass and evidence shows that it was widely dispersed across continental Australia including Victoria, New South Wales, South Australia and Western Australia.

Two small ancestral species have been described. Sarcophilus laniarius dawsoni is significantly smaller than the currently living species. Remains have been found in South Australia, New South Wales, Queensland, Northern

Territory and Victoria.
Sarcophilus dixoni spp. Is equivalent in size to modern devils but differs in dentition (teeth) and skull structure. This species has only been described from remains found in Victoria.

A theory put forward in 1877, upon the discovery of fossil remains in Wellington Caves, New South Wales by Richard Owen (Owen and Pemberton, 2005), a palaeontologist of the time suggests that the two Sarcophilus species may have coexisted at one time. It is not known if the currently living species evolved from these smaller species, a post ice age dwarfing of Sarcophilus laniarius or the dwarfism of an unknown species.

Australia has been isolated from other continents for 80 million years, drifting north from the great southern super continent 'Gondwanaland' undergoing a different set of evolutionary parameters that resulted in the success of the ancient Marsupials (pouched mammals) and Monotremes (egg laying mammals) rather than the Eutherian (placental) mammals.

Fossil evidence exists to support the theory that devils ranged right across the continent of Australia up until 5000 years ago. It appears that the species successfully exploiting all bioregions of Australia. Since the sea level rose at the end of the last ice age and flooded the Bassinian Plain (the Bass Straight land bridge that historically connected the island of Tasmania to the main Australian land mass) the species became geographically isolated into two populations. One population in Tasmania is still extant. The mainland population is believed to have suffered extinction facilitated by competition with dingoes (Canis lupus dingo).

Current genetic evidence suggests that a very small number of individuals arrived on Australian shores between 3500 and 5000 years ago. These dogs bear a similarity to New Guinean Singing dogs and the same species is found in Indonesia. It is believed that the species arrived in Australia through indigenous trading or by accidental introduction (sinking fishing or trading boat). Judging by such limited genetic diversity scientists believe that it could have been as little as 6 individuals introduced that went on to disperse across Australia. Dingoes are not found in Tasmania as the Bassinian plain was flooded and Tasmania became an island around 12,000 to 15,000 years ago.

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Dingoes are adaptable with a tightly maintained social structure. This social predation was much more successful for bringing down the highly mobile large marsupial prey such as Kangaroo than the solitary behaviour of the smaller devil species. Dingoes may have also been better at dealing with the changing nature of Australia. The dense Gondwanan rainforests were making way for an arid, dryer Australia; this change may have been facilitated by ongoing indigenous burning regimes that promoted the dominance of different plant communities such as grasses and Eucalyptus. After tens of millions of years devils became extinct on the mainland of Australia remaining only on the island of Tasmania.

The last devil is believed to have died in southern Victoria around 380 to 400 years ago. Fossil remains from Devils Lair Cave in South Western Australia shows that devils were found in that region at 5000 years ago.

General Characteristics

Tasmanian devils are the largest living marsupial carnivore the approximate size of a solid squat dog. Males are generally larger at 8-10 kg but have been recorded as large as 14kg! Powerfully built, the males are characterised by a massive head and chest. The head and neck alone can account for as much as 40% of their weight. The jaw line of the males is also much squarer than the smaller females. Females average 6-7kg and are more proportionate in their build. A large head and powerful jaws give them a fierce appearance but they are ideal adaptations. Devils are Australia's only specialised mammalian scavenger, fulfill a similar niche and share similar morphology to brown hyenas or wolverines. They consume all parts of a carcass except the largest bones. Fur, bone shards and grey coloration make devil faeces easily distinguished from other Tasmanian species.

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A Tasmanian devil has 42 teeth in total, which is the same dentition as the canids.

I 4/3; C1/1; PM 2/2; M4/4 or 4 incisors top, 3 bottom, 1 canine top and bottom, 2 premolars top and bottom and 4 molars top and bottom on each left and right half of their jaw. The single set of teeth continue to grow throughout their life and are fully erupted from their jaw at 2 years. A devil can be accurately aged by the degree of eruption and then wear of each tooth. By the age of 5 years (the life expectancy of a wild devil) the teeth are badly worn or damaged and in some cases they have fallen out. A devil with damaged or missing teeth is less capable of competing and will therefore slowly starve.

Devils are equipped with a pentadactyl (five digits) front limb but they do not have an opposable thumb. Each front digit has a short sharp claw which allows the species to dig effectively for denning and foraging. They are also capable of firmly grasping prey and food items and facilitating grooming. They also have partial webbing between the first and second knuckle which may also facilitate the use of the front limbs for digging and swimming. Devils are quite powerful swimmers, paddling 'dog' style with their front limbs and trailing their rear limbs behind. Devils will generally swim across a water source rather than walking a distance around it.
The rear limbs are shorter than the front limbs which gives the species a Hyena like stance. The rear limbs are equipped with four digits and are not used for grasping. The structure of the rear limb is radically different from the front and facilitates climbing.

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The square foot prints and the pattern of 2-1-1-2-1-1 of the unusual gait is a characteristic spoor of the species.

The front limbs move independently of each other in a left right pattern but the back legs move together. It is a very unusual gait that is thought to have evolved from tree climbing ancestors rather than ground dwelling. The gait is also very efficient burning little energy as the animals covers large distances each night. Devils are also reasonable sprinters and can run at 25-35km/hr for many hundreds of metres. They have excellent stamina and can run at around 10-12km/hr for several kilometres. Much of their hunting is believed to revolve around their stamina and stealth rather than out right speed. One paper suggests that devils snap at their prey chasing it down over a reasonable distance. Despite this devils are opportunistic predators so they would be killing weak and injured animals long before fit and healthy specimens that require long and dangerous pursuits.

The species is also very fond of water and are powerful swimmers. A biologist witnessed a devil powerfully swimming across the 50m expanse of the Arthur River on the west coast of the state. Devils also utilise the evaporative and cooling effects of water on hot days and will also paddle and dangle their front limbs in water.
Devils are also characterised by their unusual carbon black coloured fur in contrast to the asymmetrical and individual white markings on the chest, flank and base of tail. Not all devils have these markings as around 5% of the population are all black. Of those that have white markings no two are the same. There are several theories but the white probably aids in the break up of an otherwise characteristic silhouette making devil's camouflage far more effective. It is also believed that the markings may aid in recognition between individuals.

Devils are solitary by nature, hunting alone. They are a gregarious species and a number of animals will congregate on a carcass. Around the carcass a very dynamic order develops between individuals rather than the rigid hierarchy that social animals like dogs develop. Most of the vocalising and squabbling that devils are famous for is ritualised threat display or bluff. Devils have been shown to have 11 vocalisations and 20 postures. Posturing is therefore just as important in devil communication as vocalisations. The vocalisations range from soft barking snorts and monotone growling to full blown screams. Devils also use visual and chemical signals in communication. They have an ano-genital scent gland at the base of the tail. They scent mark by dragging this scent gland across the ground. Devils are thought by people to have poor eyesight. All evidence suggests that they have black and white vision that is movement dependent. The white markings across the chest and abdomen would exaggerate the posturing and the contrast would be distinctly visible at night.

The most dominant animal in a feeding aggregation is not usually dislodged from the carcass until it has eaten its fill. A devil is a gorge feeder like most carnivores and can easily gorge approximately 40% of its weight in 20-30 minutes. Digestion can not occur this rapidly so the abdomen swells impressively which usual results in the animal waddling off from the carcass.

The diet of Tasmanian devil is very opportunistic. Devils will scavenge carrion, invertebrates, fish, birds, fruit and vegetation as well as predate on smaller, weak and injured or naive mammalian prey. Of a carcass a devil is capable of digesting the flesh, bones and fur. Young devils are much more agile climbers than adults so their diet includes arboreal mammal and invertebrate species, birds and eggs. Juvenile devils learn quickly through vocalisations and appears to learn through repetition to congregate in a feeding aggregation around a carcass. Young devils can also be very diurnal in their behaviour and therefore avoid a lot of competition with the larger more experienced adult devils. Diurnal and arboreal behaviour puts devils in competition with Spotted-tail quolls which at 3-7 kg can also be threatening to a juvenile.

Distribution

Tasmanian devils are endemic to the island state of Tasmania. Tasmania is located approximately 300km south of mainland Australia. Devils exist in all 16 bioregions in Tasmania in various densities. They do not exist on any of the offshore islands

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Density
The density of Tasmanian devils varies dramatically throughout the state. The highest densities are in the eastern areas and the far North West tip.

Both areas of high densities are in lower rainfall area and also in more open dry sclerophyll, woodland or coastal areas. The milder and on average warmer areas probably support more herbivorous prey and therefore more devils.
Devils do not occur naturally on any of the offshore islands in Tasmania. It is believed that they are not large enough to support the diversity of fauna required to have a highly mobile opportunistic predator such as the Tasmanian devil. Badger Island which is part of the Furneaux Islands, a group of 52 islands that stretch across Bass Strait does not therefore have devils naturally. The animals found on this island are reputed to have been illegally relocated from the north east of Tasmania around twenty years ago by farmers for the purpose of removing dead domestic stock. These animals were recently trapped up and relocated back to the Tasmanian mainland due to the effect that they would have on the delicate island ecosystems not adapted to their presence.

In the last 10 years the devil population has been heavily hit by a disease DFTD (Devil Facial Tumour Disease). This has reduced their population by 50% in high density areas which now classifies the species as being vulnerable or threatened. Scientists with the DFTD Task Force (Department of Tourism, Heritage, Arts and Environment) suggest that the current densities may reflect the map below.

Density has been recorded as high as 3 to 4 animals per square kilometre. This makes the population much denser than comparable species such as Hyena or Wolverine. Studies presented in www.wolverinefoundation.org suggest that Wolverines may only have a density of 1 animal per 100 square kilometers. It also may mean that Tasmanian devil may be the single most important fauna species in Tasmania (Mooney, 2004).

Home Range and Movement

Studies show that devils are not a territorial species. A territory is a defended core of home range. Devils have a fixed home range of 8 to 20 square kilometres and a small area of mobile territory or personal space around themselves and females around the den when they have young. It is not fully understood how devils arrange themselves in the landscape. It is thought that the home range of one devil overlaps with another heavily. In these areas of overlap devils will utilise a common latrine site (an area where many individuals all urinate and defecate) this is not common in the animal kingdom and is usually restricted to animals such as Hyena or honey badgers and other species similar in the ecological niche in which devils fill or share some similarity with through convergent evolution. These latrine sites occur at a water source or the convergence of two major paths that devils regularly follow in their nightly movements. These latrine sites may suggest at least a degree of territoriality and are probably a visitor book telling transient devils the density of the area and the availability of females and number of competitive males.

It is also theorised that the home range shape and location may be dependent on the availability of prey species. It appears that male and female devils have a similar sized home range and males who have greater size and energy demands get the resource they require by feeding for longer on each carcass. The availability of den sites may also be a controlling factor.

Radio tracking shows that devils travel 10-20 km per night within their home range. This movement can be as little as 3.2 km and one male during December and January when the young disperse from the den was observed traveling 50 km per night to find food. The typical pattern of movement appears to include the animal leaving its den shortly after dark and at a steady lope of around 10 km/hr using predetermined tracks to investigate known food sources. Bursts of speed are intermingled with periods of lack of motion of around 30 minutes which suggests periods of ambush style predation. Towards the end of the night the devil sets a rapid non-stop lope which leads it back to the den at around dawn. Most studies suggest that the peak times of behaviour are around the periods of dawn and dusk.
It is also not known what distance the young disperse from the maternal den to establish their home range.

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Photo - Chris Coupland ©2005

Denning

Devils appear to occupy 3 or 4 dens in their home range. Dens range from hollow logs, dense vegetation, thick grass tussocks, caves to abandoned wombat burrows and burrows that the devils dig themselves. Once a den is established it is utilised frequently for life and in some areas a particularly favorable location of a maternal den may have been used for hundreds of years. Females with young are tied to one maternal den. Other devils move around, alternating between dens. Mothers will move their young from one den to another by carrying the young on their back if stressed, but this greatly increases their vulnerability.

A den dug by a devil tends to be quite simple in structure, plunging down quite quickly and then opening out into a single nesting chamber. Inside the den the devil drags large quantities of leaf material to establish a nest. They are meticulous in the arrangement of the nest and will fuss with it constantly bringing in fresh material and pushing out wet bedding.

Because of the nature of devil denning, habitat disruption may have long lasting impacts on den site selection and infant mortality. This has been supported by studies into wolverines presented on www.wolverinefoundation.org. If human encroachment, forestry or agriculture removes prime den sites then it creates instability in the population.

Reproduction

Tasmanian devils have a highly complex reproductive cycle. Devils are marsupials so they give birth to undeveloped live young after a short gestation period that then develop externally inside a marsupium or pouch.

The breeding season usually lasts for 3 weeks commencing in late February with mating occurring around the second or third week in March. The mating ritual is often described as a violent affair but is usually characterised by ritualised combat between the male and female. Males will compete heavily with each other and can inflict injuries to each other's head, neck and rump. Injuries at other times of the year are rare.

It appears that females solicit the males and select their mates not just on physical strength but on experience. This competition usually means that a male mates with more than one female. This means that a female optimises the genetic strength of her offspring by maximizing the number of sperm donors.

Whilst a female is coming into oestrus she goes through a number of distinct behavioural changes. Initially the female starts developing a roll of loose skin on the back of her neck which ultimately the male will grasp to gain submission from her. The pouch also reddens and deepens in preparation to receive the young. Then the female will start becoming very cautious and elusive as she slowly stops eating and starts readying the den by collecting nesting material and slowly becoming more and more lethargic.

During this time males start moving in and trying to solicit for her attention. This process is extremely vocal as the potential pair move through a highly ritualised combat in which they go through the same motions as a fight but without the impact. Through this process a male can 'prove' to the female that he is physically and genetically fit as well as experienced. Once the male can move to grasp the skin roll on the back of the neck, the female will subordinate to him. He can then drag her back to the den and copulate with her.

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Photo - Harvey Ord, devils @ cradle ©2006

The copulation is continuous for between 12 hours and 5 days. When the male is not copulating he takes up a position between the entrance of the den and the female. This mate guarding behaviour prevents other males from mating with the female for as long as the male can hold the position. Eventually he is driven off by the female, another prospective male or both. Usually over a 10 day period a female can mate with between 1 and 4 males. Gestation in Tasmanian devils averages 21 days. The young are born roughly the size of a grain of rice. Devils will birth many more foetus than they have provision to raise and have been observed birthing between 18 and 40 foetus over an hour period. There are 4 teats (nipples) in the rearward facing pouch, so a devil can raise a maximum of four young in a litter.
During the birthing the female will arch her back dramatically as she gives birth. She holds this position for around an hour and then apparently exhausted she will ball up tightly. This balling up may also serve the purpose of bringing the pouch and the cloaca closer together which may heighten the chance of some of the young successfully gaining a teat to suckle.

It may not necessarily be the fastest foetus that succeeds but the ones with the strongest instinct to survive. If a foetus can complete the treacherous journey from cloaca to pouch and fuse to a teat it is highly likely that they will have the natural instinct to hunt and scavenge successfully when they leave the maternal den.

Unusually for a marsupial the large number of young can also have many males that sired them so it is not necessarily the same male that sires the whole litter. This optimises the genetic strength of the offspring.

The young stay in the pouch for a period of around 16 weeks. The young are then deposited in the maternal den. To prevent predation the young instinctively dig narrow side dens into which they can run if there is a threat. It appears that in these side dens only the mother can get them out with a series of gentle vocalisations as any other devil would not have the young's recognition. This protects the young not only from other predatory species but also marauding male devils that have been known, in their desperation, to kill juveniles who would otherwise be defenseless.
Initially after exiting the pouch the young are still on a milk diet. Within approximately two weeks the female starts returning with some skin and fur for the young to chew. This may start readying jaw muscles and behaviours to manipulate prey. Very quickly she will start to bring flesh and whole carcasses back to the den for her young to eat. The young usually wean in a matter of weeks and 20 weeks after being deposited in the maternal den the young are independent.

One theory suggests that the female abandons her young at this time. Another suggests that she has lost so much weight that the young out compete her and drive her away. The young usually stay together in the same den as a sibling group before they disperse.

Mortality

Mortality in juvenile devils is very high. It is believed to be around 75% of young die before 12-14 months of age. This high mortality comes through starvation and predation from introduced pest species, masked owls (Tyco novahollandiae) and Spotted-tailed quolls (Dasyurus maculatus). The mortality comes from the young failing in their recruitment into the natural population not the lack of maternal care.

The occurrence of starvation may be exaggerated by feeding aggregations which require some experience to successfully negotiate. If a devil is too aggressive it risks injury in a confrontation with a larger more experienced individual. If it is too meek then it stands a chance of being out competed by more experienced individuals and not able to secure food around a carcass. In this circumstance it is likely that most of what juvenile devils eat is insects foraged either aboreally or terrestrially.

Success may also depend on the level of social interaction in the den. If a female has only 1 or 2 young in a litter then these may not be as experienced at communicating and ritualised combat as a litter of 4 may be. Play fighting between juveniles in the den provides valuable rehearsal for skills needed in later life.

Juvenile devils also have a high mortality rate on the roads, particularly around the months of December through to March when high levels of competition lead to exploiting dangerous food sources.

Mortality of adult devils usually comes through an inability to compete. This may be exaggerated by a loss of mobility through weakened and worn joints or worn and damaged teeth. It may also come from a male dying off throughout or immediately after the breeding season. These weaker and exhausted males also have high mortality rates on the roads as they are also drawn to the easy but dangerous food sources.

Feral pests can also have a huge impact on both adult and juvenile devils. Dogs can easily kill devils.

Other devil info links

See the devils of devils@cradle on the Discovery Educator Abroad: webisode: 20

UTAS

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Adult devils possess a large neck and head
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Showing an impressive set of teeth and tremendous jaw strength
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Devils@Cradle - Tasmanian Devil Sanctuary