Tasmanian Devil (10 page)

A female devil has four nipples in her marsupium and litters of three or four pups are common, which helps balance out the high juvenile mortality rate. David Pemberton found a healthy 80 per cent of two-year-olds carrying pouch young during his fieldwork study. The mother stands to give birth. Twenty or more tiny embryos leave the womb and travel up to the backward-opening pouch in a stream of mucus. The first arrivals clamp to the teats, which swell in their mouths, so that the newborns become firmly attached to their mother. This ensures they do not fall out of the pouch and is an important survival factor.

Devils are usually born in mid-April, that is, mid-autumn, ensuring they won't be weaned and have to face the world alone until long after Tasmania's challenging winter has passed. DFTD, however, has produced a dramatic shift in reproductive behaviour, with a scatter of births across the seasons rather than

Baby devils begin to grow fur when they are twelve weeks old. Their sturdy tail is as
long as their torso and has important functions including balance, storage of fat and
communication. (Courtesy Collection Tasmanian Museum and Art Gallery)
exclusively in autumn, and a high number of males competing for perhaps just one receptive female.

In 1934 David Fleay managed to breed devils in captivity and wrote a fine, precise account of it:

In the first days of June four tiny, pink, naked and blind babies each a half inch in length had betaken themselves to their mother's pouch. Shortly after this the father was removed to bachelor quarters, for the mother now showed resentment at his presence by whining growls which rose abruptly in pitch and volume whenever the male attempted to enter the rock shelter. Early in August at the age of seven weeks the thick-set babies in the pouch had grown to a length of two and three quarter inches. They were still pink and hairless but now it could be seen that their tiny limbs moved actively as they clung tenaciously to the teats within the pouch. They also made slight squeaking noises and with increasing bulk the hind quarters of one quadruplet projected from the pouch as the mother moved about.
    Meanwhile she had become somewhat fastidious for a Devil, disdaining raw meat but delighting in rats, birds, eggs, frogs and rabbit heads. Towards the middle of August a great change came over the appearance of the youngsters as the ear tips and then other regions of the skin began to show dark pigment. The pouch too, developing with the family, was far more relaxed and roomy. At eleven weeks the dark pigment of the young had become sufficiently pronounced to throw into strong contrast the future white chest and rump markings. The quiet nervous mother accepted the frequent handling with no sign of resentment. Progress of the little Devils was now quite phenomenal and on October 1st at fifteen weeks of age they first released their till then continuous grip on the teats. They were well furred and their eyes had opened. From these observations it is obvious that the mother must carry her cumbersome family with her for at least fifteen weeks after their birth. But from this time on the youngsters may be left at home in the nest, allowing the mother the freedom necessary for successful ‘scrounging'.
    When lifted away from the parent the youngsters uttered anxious yapping cries and on being released again clung quickly to the fur of her sides with teeth and fingers—the fore-paws having unusual grasping powers so that the young Devils are expert climbers. On being disturbed from sleep when sheltered by the mother's body, the little fellows lost no time in gripping her extended teats, from which it was almost impossible to dislodge them until firm pressure with a fingertip over the nostrils caused their mouths to open. At the age of eighteen weeks the ‘play age' was apparent . . . At twenty weeks they were seven and three quarter inches in body length with small tails adding a further three inches. They still clung tenaciously to the mother's teats when drinking . . . It was five months before they ceased to rely on their mother's milk for nourishment and unfortunately we lost two of them before they had abandoned the maternal apron strings. One squeezed through the chain netting of the enclosure and was never heard of again while the other sickened and died. The mother and remaining two youngsters showed the thorough scavenging traits of their kind by immediately devouring the whole carcass, except the head, of their deceased relative even though food was plentiful.
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Devils are weaned in summer, between December and February, after which they disperse widely, but with a higher proportion of females remaining in the natal areas. Up to 60 per cent die before reaching maturity, according to Guiler. Even so, the sudden increase in numbers over summer can give the appearance of a plague, because juveniles are more crepuscularly active than adults and at dusk are regularly seen on roads, scavenging in paddocks or on beaches and around farm complexes.

Newly weaned devils become solitary at once. They are agile foragers, taking a wide variety of small invertebrates and vertebrates, and their excellent climbing ability enables them to obtain food from trees, such as grubs, and eggs from birds' nests. They are fully grown and mature by the age of two.

The uniqueness of a solitary animal surviving through communal feeding sets the devil apart from other carnivores. Young devils quickly learn to congregate at the site of a carcass, drawn by the scent and, just as importantly, the vocalisations of those that have already arrived at the site. Conflict over a carcass is avoided through a ritualised behaviour ensemble.

Young devils are agile foragers and good climbers. This picture was taken at
Mrs Roberts' Beaumaris Zoo in the early 1900s. (Courtesy Collection
Tasmanian Museum and Art Gallery)

Young devils, because they are active at dusk, have the advantage of arriving at food sources before the more competitive adults. This, however, puts them into competition with spotted-tailed quolls, which are also active diurnal feeders.

Feeding devils communicate with each other through a range of visual postures, vocalisations and a suite of chemical signals. It was once assumed that dasyurids made little use of visual communications because they are nocturnal. Devils have night-adapted eyesight and their white chest and rump flashes are distinctly visible at night. Interaction between devils at feeding sites takes the form of a ritualised contest, with the dominant feeder not being displaced until it has gorged itself.

A devil eats up to 40 per cent of its body weight per meal every two to three days. Eating such a large quantity of food in a short space of time—about half an hour on average—often results in the animal waddling off with a distended belly and lying down not far from the feeding site; a devil in this state is easy to approach. It is likely that the absence of other large predators has facilitated this form of feeding, even during the long period when thylacines were Australia's largest carnivore. This lends some support to the belief that thylacines ate only choice parts of their prey, leaving the rest to devils and other scavengers.

Being a scavenger able to digest a wide variety of food matter—flesh, fish, bone, invertebrates, fruit, vegetation—was an advantage to the devil's survival. It may also be that the thylacine's narrower food base (and less productive breeding cycle) meant that it existed in comparatively lower numbers, leaving it more vulnerable to changed circumstances (human predation) than the devil.

The number of devils feeding together is generally determined by the size of a carcass: groups of two to five are common. The first arrival is the dominant feeder (unlike communal hyaena feeding, where the higher ranking clan members feed before subordinates), which makes way for a challenger once it has gorged itself. The size of the carcass affects the extent to which the feeding devil will chase off a challenger: the feeder defends the amount of food it needs, not the entire carcass.

Satiation, rather than dominance, is the most likely information conveyed by the ritualised interactions. This means all devils, small and large, resident and transient, can feed together. It is an efficient way of sustaining a population.

David Pemberton was the first to make scientific field studies of devils feeding in the wild. The absence of unrestrained aggression while feeding, and the complex behaviour occurring in its place, was a critical discovery, overturning popular (and some professional) perceptions of the animal, as in this supposedly informed 1984 account of feeding devils by a popular natural history author: ‘They behave like a brawling mob, having, so far as anyone knows, virtually no social organisation or restraining instincts'.
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Pemberton recorded only one instance of physical injury in 119 interactions during feeding, with one animal chasing and biting another on the rump. On two occasions he also observed jaw-wrestling, where devils stood on their hind legs with forepaws on each other's shoulders or chest and their jaws interlocked. The animals vocalised constantly while shaking their heads from side to side. Although there was no obvious physical damage to the animals, the nature of the interaction appeared as if it could have caused extensive damage to muzzles or jaws. On each occasion the defeated animal ran off into the bush with its tail in the air and fur fully erect, with the winner pursuing it and biting its rump whenever it was close enough.
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Examination of 150 trapped animals showed that 6 per cent had suffered injuries consistent with fighting during feeding or breeding, showing enough damage to the flesh of the face to leave teeth visible. These, however, were aged males with lame hindquarters and extensive hair loss on rump and tail, suggesting a physical deterioration other than that caused by intra-specific aggression. A third showed some form of wound, such as puncture holes on the back and rump and shortened, hairless tails. It doesn't automatically mean that all the wounds were obtained while feeding; in fact, most wounds occur during the breeding season.

Pemberton recorded eight vocalisations between initiators and recipients at carcasses: a ‘snort' made by expelling air through nostrils and mouth; a short, deep, low-intensity ‘humf growl', often repeated; a short, deep, high-energy ‘bark', seldom repeated; a ‘clap' made by snapping the jaws together; monotone, vibrato or crescendo ‘growl-whines'; a ‘screech', associated with defeat; a ‘sneeze' and a ‘yip'.
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Pemberton also identified some 20 postures that reinforce the elaborate nature of the feeding interactions. They include:

• Neck threat—one nips at the neck area of the other, without making contact. These nips are repeated and the recipient responds by shouldering the initiator or attacking it face on.

• Gape—animals open their jaws for a few seconds as inter– actions take place.

• Lying down—the initiator of the behaviour lies down on its belly with the fore and hind feet extended. These animals are in full view of the possessor of the carcass, but do not physically interact with it.

• Sitting—the initiator sits and stares in the direction of the recipient, often combining this with gaping and lying down.

• Head and tail positions—these vary from a frequent ‘head-up-tail-down' posture to a less frequent ‘head-up-tail-straight' posture. Their intensity seems to be reflected by the degree to which the fur on the tail is raised. In some circumstances the legs are bent sufficiently for the belly to scrape on the ground.