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Chapter 1 – The Tasmanian devil (Sarcophilus harrissi)

1.2 Tasmanian devil – what is known?

1.2.4 Tasmanian devil aggressive behaviour

Recent media images and stories of devils have focused on their apparent savage, biting and snarling habits, when in fact the record shows they are generally timid, sensitive and easily subdued animals. Guiler who handled more than 7,000 devils ‘found them docile to the point of being lethargic and could be handled with ease’.37 However, Guiler’s observations published in 1970 did note ‘[i]ntraspecific fighting results in severe facial injuries and may lead to death’.38 Contrary to this, in his book The Tasmanian Devil published in 1992, Guiler states ‘[f]eeding is accompanied by much squabbling, loud

34 Pemberton D & Renouf D, 1993, A Field Study of Communication and Social Behaviour of the Tasmanian Devil at Feeding Sites, Australian Journal of Zoology, Vol 41(5), pp 507-526 p 507

35 Owen D & Pemberton D, 2005, Tasmanian Devil, a unique and threatened animal, Allen & Unwin, Crows Nest, Sydney, p 13

36 Jones ME and Barmuta LA, 1998, Diet overlap and relative abundance of sympatric dasyurid carnivores: a hypothesis of competition, Journal of Animal Ecology, Vol 67, pp 410-421

37 Nowak RM, 1999, Walker’s Mammals of the World, Baltimore, Johns Hopkins University Press, p 64 cited in D Owen & D Pemberton, 2005, Tasmanian Devil, a unique and threatened animal, Allen & Unwin, Crows Nest, Sydney

38 Guiler ER, 1970, Observations on the Tasmanian Devil, Sarcophilus harrisii, Australian Journal of Zoology, Vol 18, pp 49-62, p 60

screams, growls, jaw chomping, jostling and general aggression’39 but ‘[n]ot much serious damage is inflicted except for nips and bites, much of the aggression being a ritualistic display’.40 Guiler concluded that intense competition for limited food resources might have been the cause. Lack also attributed the possible causes of fighting to food shortages.41

Pemberton and Renouf in their three year study of devils in the wild, the first description of wild devils’ social interactions, found little physical damage resulting from communal feeding and little evidence of injury in animals they trapped.42 The study was carried out at Mt William National Park where it was estimated over 200 devils were present. 43 The trapping occurred every four months over the study period. Examination of trapped animals showed that 29.5% had scars or open wounds with all but one appearing on males. The records of physical damage are shown in the Table 1:1 below. Of the wounds only 6% were recorded as open and bleeding. Overall the damage sustained to the muzzle (48.4%) was the equivalent to that sustained to other parts of the body. Moreover, in a study of 119 interactions at a feeding site, set up by the researchers, only one encounter resulted in physical damage and that was to the rump of a fleeing animal.

39 Guiler ER, 1992, The Tasmanian Devil, St. David’s Park Publishing, Hobart, Tasmania, p 8

40 ibid.

41 Lack D, 1954, The Natural Regulation of Animal Numbers, Clarendon Press, Oxford cited in ER Guiler, 1970, Observations on the Tasmanian Devil, Sarcophilus harrisii, Australian Journal of Zoology, Vol 18, pp 49-62,

42 Pemberton D & Renouf D, 1993, A Field Study of Communication and Social Behaviour of the Tasmanian Devil at Feeding Sites, Australian Journal of Zoology, Vol 41(5), pp 507-526, p 519

43 Cited Pemberton, D, 1990 in ibid.

Table 1:1 Frequency of occurrence and location of scars and wounds on male and female Tasmanian devils44

Wound and scar location No of males with scars No of females with scars

Muzzle 43 16

Ears 4 4

Shoulders 2 0

Claws missing 3 2

Legs 1 0

Back 7 5

Rump 15 4

Tail 12 4

Aggressive behavior in animals both in attack and defence is found in two areas, sexual competition and resource competition. Males compete for the chance to mate and for food whilst females compete for food. This behaviour is typically accompanied by visual signals and devils display an ‘open-mouth threat’ that reveals their teeth, especially canines, as shown in Figure 1:3 below, and is usually accompanied by a harsh vocalisation and a raised forepaw.45 They also neck-threat, nip in the direction of another’s neck, and walk stiff-legged.46 These displays constitute a typical high intensity threat with maximum exposure of weaponry. Devils can open their mouths 120 degrees whereas a dog can only open its mouth 70 degrees.47

44 Pemberton D & Renouf D, 1993, A Field Study of Communication and Social Behaviour of the Tasmanian Devil at Feeding Sites, Australian Journal of Zoology, Vol 41(5), pp 507-526, p 521

45 ibid, p 515

46 ibid, p 512

47 Pyers G, 2005, Life Cycles of Australian Animals, Tasmanian Devils, Echidna Books, Melbourne

Figure 1:3 Tasmanian devil open-mouth threat48

In his book Essentials of Animal Behaviour Peter Slater notes natural selection matches behaviour extremely well to an animal’s particular environment and way of life.49 If biting proved detrimental to the devil population it would have ceased being an inherited display.

However, he points out that there are factors, which can affect aggression including hormones, shortage of food, presence of rivals and contested resources.

Devils are not the only animals that display aggressive behaviour. Other animals display an armoury of antlers, horns or teeth that a rival risks encountering, if it engages in a fight. As

48 Tasmanian Devil at Taronga Zoo, Photo: Rick Stevens

49 Slater, PJB, 1999, Essential of Animal Behaviour, Cambridge University Press, Cambridge, UK

Slater states,

[a]ggression becomes easier to understand if individuals act only for their own good, indeed one might expect them to fight a tremendous amount the whole time, each being out for its own ends and careless about possible damage to others. This certainly does not occur, but the reason is probably simply just that fighting is dangerous.50

Aggression tends to be limited where it could have a dangerous outcome for either of the participants. It is therefore more usual for animals to display and threaten until the other retreats.51 As noted previously devils do not defend territories, eliminating the need to fight over territory.

Devils that did incur injuries, Guiler observed, had incredible recuperative powers from both tissue and bone damage, which meant that any damage was not sustained long term.

In observing severe wounds in poisoned devils, Guiler observed one devil with ‘both frontal bones shattered over the brain leaving a hole’ in the skull and a second devil with a wound from a .22 bullet, both had recovered from their injuries before succumbing to deliberate chemical poisoning.52 In 1992 he concluded that the main cause of premature death for devils was through human activities such as poisoning and trapping.

The recent media images, both photographs and films of devils, are taken in captivity. In this artificial environment devil behaviour is not in response to its natural environment.

50 ibid, p 150

51 ibid, p 151

52 Guiler ER, 1992, The Tasmanian Devil, St. David’s Park Publishing, Hobart, Tasmania, p 12

Animals in captivity are generally more socially intolerant. 53 Hence the devil’s reputation as an aggressive and fierce animal, ready to bite at the least provocation, may be due to the fact that most observations of devils have been in captivity in close proximity to other devils. In their natural wild state the evidence suggests they are predominately nocturnal and solitary creatures. The Tasmania devil species has survived thousands of years of natural environmental change and adaptation to now face extinction from a deadly cancer.

Other changes in the environment, as has been suggested – increased pressure for food, higher density of population and more aggressive behavior - might have accounted for an increase in biting and contributed to the transmission of the cancer but as will be shown there is no evidence that this is the case.