Thylacine (3 page)

Behaviourist Desmond Morris, former Curator of Mammals at London Zoo, has identified nine possible theories to explain the stripes of the zebra, ranging from safety in mass optical illusion through personal identification to an ingenious cooling system. The original camouflage explanation is discredited: ‘Their natural history does not fit with the explanation that has been repeated in textbooks for decade after decade.'
⁶

So, if the widely studied zebra has been a longtime victim of misinformation, what chance of a fair hearing for the elusive Tasmanian thylacine, the ‘zebra wolf'? Again, there is a certain logic in the wolf attribute, given the doglike features of the thylacine, its carnivorous nature and other features pointing to convergent evolution in the two species. But although there is no link to the canid family, the thylacine suffered through its perceived association with
Canis lupus
, the grey wolf of the Northern Hemisphere. (One striking difference is that dogs have six incisors; thylacines have eight.)

Few other animals have been so unfairly reviled and wrongly feared as the wolf. In the Middle Ages people identified as werewolves were burnt at the stake, having first been gruesomely tortured. Infection with rabies through the bite of a rabid domestic dog may have led to such identification, since both animal and human victims of the deadly virus salivate extensively and can exhibit uncontrollable, vicious behaviour as the brain becomes affected. The persistence of the European myth that wolves ate children found an echo in Van Diemen's Land. And, of course, the grey wolf is the evil protagonist of two particularly famous fairy tales.

As if all this was not enough, the wolf was and is blamed for livestock kills in those parts of Italy, Spain, Portugal, Greece and Mexico where it still exists, even though feral dog packs are the main culprits. Wolves are thought to prefer their natural prey, but the decimation of smaller mammal populations has led to an increasing dependence on livestock. Likewise, it is certain that the thylacine as a specialist predator would have an over-
whelmingly natural preference for native prey, specifically kangaroo and wallaby.

A comparison between the skulls of the thylacine and the grey wolf. Note the thylacine's
massive molars at the back of the jaw.

Similar scapegoating occurs with canids elsewhere. Thus, southern African farmers of the valuable caracul sheep sometimes enclose pastures to prevent attacks by the black-backed jackal. ‘Even so, the extent of predation by jackals here is probably exaggerated, with many of the sheep being killed by domestic dogs.'
⁷

It seems inevitable that the island's elusive marsupial predator would eventually be demonised as a sheep taker. Destructive nineteenth-century bounty schemes, set up to save sheep from the thylacine, effectively led to its extinction. Today Tasmania's sheep farmers still suffer stock losses to predators— but no-one's blamed the thylacine for a long time.

There is, however, a genuine new predator. Foxes were introduced to Tasmania in 2001, by hitching a ride on the Bass Strait passenger ferry and by deliberate human agency for the purposes of hunting. If they become established, wildlife in particular will suffer considerably.

The thylacine's already terrible image was irredeemably tarnished once it attracted the hyaena tag. Although the two have no current scientific relationship, they share an intriguing biology: just as the world's largest contemporary marsupial carnivore defies neat categorisation, so too is the hyaena a mystery, being part-dog, part-cat and part-mongoose. Like the thylacine, it has its own classification (family Hyaenidae)—and: ‘If any animal was less popular than the hunting dog in Africa during the days of the great white hunters, it was the hyena. Universally regarded as cowardly, loathsome, filthy and a dozen other undesirable adjectives, it too was persecuted as vermin . . . Along with vultures and dung beetles, it was regarded as a necessary evil'.
⁸

The hyaena and the thylacine have very little in common, despite the superficial similarity in the sloping rear quarters. The latter is permanent in the hyaena, which has shorter back legs than forelegs, but the thylacine's marsupial ability to flatten its ankle joint into an elongated foot can achieve the same lowering effect. This effect may be enhanced because ‘the rump tapers into a semi-rigid tail'.
⁹
Furthermore, thylacines were reported to have ‘a slow skulking habit. This suggestion is supported by those persons fortunate enough to have seen thylacines hunting'.
¹⁰

Needless to say, there are plenty of differences between the thylacine and the hyaena, one being the former's modest vocalisation, so different from the scary ‘mad laughter' of the hyaena, which in African folklore is associated with the witches of the night. At least the thylacine has been spared that. Anatomically it has been shown to most closely resemble a leopard, in that they both have short legs and long tails. But the hyaena link persists.
¹¹

Calling a thylacine a dingo isn't illogical either. Each is a champion carnivore uniquely identified with the vast Australian continent, although the ability of the latter to have some affinity with human beings perhaps spelled the end of the former. It is instructive to bear in mind that dingoes have long been regarded as a terrible pest to Australian farmers, because of their predatory habits and canine ability to take stock with relative ease.

The marsupial thylacine is the odd one out in that predatory threesome. Yet in the 1880s, when the Tasmanian parliament was in ferment over whether or not to introduce a bounty scheme to eradicate the thylacine, it was named by the pro-kill lobby as the Native Dingo. Again—if it hadn't been assured many times already—the thylacine's fate was sealed. It was almost everything in mammal form that people despised, feared, hated.

Now its loss is mourned. But that is not to say that there are not firm believers in its continued existence. They're out there.

2 IN THE
BEGINNING:
EVOLUTION

One of the favourite stories told by bushmen is that if you catch a tiger by the tail he cannot touch you because he has a stiff back, but as far as I am concerned I would prefer that someone else held the tail. He is a very prettily striped animal and I feel it is a great pity they are all gone.

A
RNOLD
P
ENNEY,
D
EVONPORT

T
he recent and brutally swift demise of the thylacine, a human-engineered folly, is brought even more sharply into focus when considering the length of time it took to evolve as Australia's largest extant marsupial carnivore. Its origins are shrouded in mystery, partly through lack of study.

The Australian continent began to part from the super-continent Gondwana as much as 200 million years ago, becoming fully separated about 50 million years ago and taking with it primitive marsupial stock, remnants of the earliest mammals that first appeared as small nocturnal creatures during the dinosaur-dominated Triassic, Jurassic and Cretaceous periods. A look at the dynamics of evolution will show how the thylacine eventually came to occupy its unique and seemingly too vulnerable niche.

It's generally accepted that Earth is about 4.6 billion years old, having been born out of a hydrogen-like solar nebula as a mass that condensed to a protoplanet happening to contain carbon-based chemicals. These were to become essential for life. The earliest evidence of this is found in rock: microscopic single-cell fossils, without a nucleus, occur in the Warrawoona Range of Western Australia. They are up to 3.8 billion years old—in relative terms, almost as old as the planet itself.

In time single cells developed a nucleus, the protective repository of deoxyribonucleic acid, aka DNA, the building block of replication which is so exciting cloning advocates early in the twenty-first century. Indeed, thylacine DNA is being used in a major and controversial Australian thylacine cloning project (discussed fully in Chapter 14).

Elementary sexual reproduction was the next step along the evolutionary path. Many life forms so created were still incredibly small. Yet it took the great bulk of the Earth's known age for life to advance to that stage. This is known as the Cryptozoic. The Phanerozoic is charted to include the present and can be said to have commenced about 570 million years ago. It is defined on the official Geologic Time Scale as being the time of ‘evident life', thus distinguishing it from the Cryptozoic's ‘hidden life'.

Earth's timelines are as scientifically intricate but as continually shifting as are the classifications of living things. One is bound up in the other. In a study of a single species like the thylacine, it is advantageous to be aware of the fluidity of fact, as evinced by the scholars of geology and zoology, palaeontology and evolution biology.

Archaeological and geological timeline showing the place of the thylacine in prehistory.

The Phanerozoic comprises three eras. They are the Palaeozoic (lasting some 300 millon years: think plants, fish, amphibians); the Mesozoic (lasting some 200 million years: think reptiles, birds, flowering plants); and the Cenozoic (65 million years and counting—think mammals). Although these eras are constructed according to the life forms that define them, it's more the case that changing planetary conditions defined the evolution of those life forms.

To this self-evident organic interrelationship of land, air, sea and life must be added the relatively recent discovery of plate tectonics and continental drift, which play a central role in explaining Australian marsupial evolution. Until about the middle of the twentieth century, prevailing scientific opinion was that land masses were immovable. In fact the world's six continents have variously been one megacontinent, Pangaea, two supercontinents, Gondwana and Laurasia, and numerous other combinations, all of which have played definitive parts in the evolutionary jigsaw.

Joined to comprise a shifting Gondwana were today's South America (once land-bridge linked to North America), Africa, Antarctica, India and Australia. This is thought to explain the marsupial journey—that the marsupials that originated in North America and dispersed successfully into South America travelled across then-habitable temperate Antarctica to Australia. Unfortunately the fossil record doesn't unequivocally support this; hardly any marsupial fossils have been found in the now frozen continent, which nonetheless as part of Gondwana hosted a great variety of vertebrate life.

Is the thylacine genetically linked to those earliest North and South American marsupials? Certainly, carnivorous predators evolved in South America, once that continent itself became isolated about 40 million years ago. Its family Borhyaenidae ranged in size from mink to bear, animals with large teeth and short limbs. Deriving from those specimens were the sabretoothed marsupials: large, speedy and with powerful sets of teeth. Interestingly, the long-extinct Australian marsupial lion
Thylacoleo carnifex
(some believe it still exists!), apparently descended from either pygmy possum or wombat stock, had equally fearsome teeth: very large incisors and blade-like cutting carnassials. These teeth ‘represent the most extreme specialisation of any known mammalian carnivore'.
¹

Prior to the discovery of continental drift, Australia's marsupial presence was explained with a theory of island-hopping from Asia. Then in the 1920s it was proposed that Antarctica might have acted as a land bridge. In 1981 a 40 million year old marsupial fossil was found on the Antarctic's Seymour Island. Belonging to a marsupial family previously known only in South America, it was a hugely significant find, all but proving the land bridge theory.

Recent discoveries confirming the existence of marsupial fossils in the Gobi Desert have complicated matters. The fragments were first discovered at Mongolia's Ukhaa Tolgod fossil site in the 1920s by American explorer Roy Chapman (upon whom Indiana Jones is modelled), but it was not until the 1990s that the tiny dinosaur-era mammal
Deltatheridium
was positively identified as a very remote relative of kangaroos and possums. Does this suggest revisiting a possible Asian origin for the marsupial?