Thylacine

The image of the Thylacine (Thyiacinus cyno-cephalus) occupies a place of honor in the Tas-manian coat of arms, but in life, fear and ignorance allowed the species to be driven to extinction (Dixon, 1991). Otherwise known as the Tasmanian tiger or Tasmanian wolf, the thylacine was the largest carnivorous marsupial to have existed in historic times. The thylacine ranged over much of Australia, Tasmania, and Papua New Guinea, and it was the top predator in those areas before the arrival of humans. The combined effects of competition, habitat destruction, and relentless persecution by humans led to the demise of this species less than a century ago. The story of the thylacine is a classic example of mankind's love-hate attitude toward other predators. Although they are admired for their strength and untamed nature, predators are generally feared and often resented as competitors for resources.

The thylacine superficially resembled a large dog. It was a sleek animal, weighing 15 to 30 kg, with short, dense, yellowish-brown fur marked by distinct black stripes across the back and rump. The tail was long, broad-based, and somewhat rigid. Although the head was doglike in appearance, the jaws were capable of an unusually wide gape. Like all marsupial mammals, the thylacine gave birth to its young at a very immature stage. After birth, a litter of two to four young completed their development in their mother's pouch, until they were mature enough to follow their mother or stay in the den by themselves (Smith, 1982).

The thylacine's closest surviving relatives are other carnivorous marsupials of Australia, such as the Tasmanian devil (Sarcophilus har-risii) and the quolls (Dasyurus spp.). The extinct carnivorous marsupials from South America were more distant cousins (Nowak, 1999). Thylacine fossils have been found on mainland Australia, Tasmania, and Papua New Guinea, and aboriginal rock art confirms that the species existed in Australia during the time of the first human inhabitants. But by the time Europeans arrived, the thylacine's range had already been reduced to the island of Tasmania. Competition with dogs (Canis familiaris dingo) introduced by the Aborigines was probably a significant factor in reducing the thylacine's range, and the species may have survived longer in Tasmania in part because dingoes were not introduced there.

European settlers, who arrived in Tasmania at the beginning of the nineteenth century, set out to tame the wilderness and reshape the landscape in the image of their homelands. The thylacine was perceived as a wolf among their sheep, and it acquired a notorious reputation as a killer of livestock, despite the fact that dogs were much more destructive. There was no room for predators in the pastoral paradise envisioned by these settlers, and therefore a bounty was set for their extermination. The peak of the killing occurred in 1900 (Smith, 1982). Indiscriminate killing coupled with population fragmentation and habitat loss caused the thylacine population to decline rapidly. Disease may also have contributed to the demise of this decimated, fragmented population. A few naturalists recognized the precipitous decline of the species, but the concerns of ranchers took precedence. The last shooting of a wild thylacine occurred in 1930, and the species was granted protected status in 1936—a little late.

Much of what has been recorded about the habits and ecology of the thylacine has come from the observations of trappers, hunters, and ranchers, and there may be a certain lack of objectivity in their accounts (Jones and Stoddart, 1998). It is thought that the thy-lacine was primarily a nocturnal, solitary hunter. Pairs or small family groups were occasionally observed, and lairs were found in rock crevices and hollow logs. In Tasmania, the thy-lacine's range appears to have extended from the mountaintops to the coast (Dixon, 1991). Grasslands and open woodlands were probably favored as habitat rather than dense forest.

From examination of the anatomical evidence, Jones and Stoddart (1998) and Jones

(1997) concluded that the thylacine's reputation as a sheep killer was significantly overstated. The thylacine's teeth and limbs suggest that its prey was most likely to have been small relative to its body size. It probably hunted its prey in a pounce-pursuit manner in fairly open habitats, and it killed with a crushing, penetrating bite. The remains of small- to medium-size herbivores (less than 5 kg) have been found in cave deposits along with thy-lacine remains. Hunters reported that thy-lacine stomach contents included kangaroo and even echidna (Tachyglossus spp.) remains (Smith, 1982; Dixon, 1991).

Individual animals survived in zoos for up to nine years, but they never bred in captivity. The last known thylacine, a female named Benjamin, died in a private Hobart zoo in 1936 (Dixon, 1991). The fact that even the sex of the world's last thylacine was misidentified is telling of the ignorance regarding this species. Expeditions have been mounted in search of the thylacine, and many alleged sightings have been reported, but there have been no substantiated observations of the species for more than sixty years (Rounsevell and Smith, 1982; Smith, 1982).

Now, in what might become one of the most intricate (and costly) biological feats ever attempted, scientists at the Australian Museum have proposed a plan to resurrect the thylacine. DNA will be extracted from museum specimens; the genome will be sequenced and used to create a living thy-lacine. The project has thus far been successful in DNA extraction, but the challenges of reconstructing chromosomes and a surrogate pregnancy still lie ahead. The project plan also stipulates that habitat preservation must be a priority in order to provide for a new thy-lacine population. Critics abound. Although the scientists are optimistic, they themselves acknowledge that it is likely to be decades before the project is completed (Colgan and Archer, 2000).

—Julie Pomerantz

See also: Agriculture and Biodiversity Loss: Industrial Agriculture; Alien Species; Carnivora; Convergence and Parallelism; Extinction, Direct Causes of; Mammalia; Preservation of Species

Bibliography

Colgan, Don, and Mike Archer. 2000. "The Thy-lacine Project." Australasian Science 21:21; Dixon, Joan M. 1991. The Thylacine: Tasmania's Tiger. Melbourne: Museum of Victoria; Guiler, Eric R. 1985. Thylacine: The Tragedy of the Tasmanian Tiger. Melbourne: Oxford University Press; Jones, Menna E. 1997. "Character Displacement in Australian Dasyurid Carnivores: Size Relationships and Prey Size Patterns." Ecology 78:2569-2587; Jones, Menna E., and Michael Stoddart. 1998. "Reconstruction of the Predatory Behaviour of the Extinct Marsupial Thylacine (Thylacinus cynocephalus)." Journal of Zoology 246:239-246; Nowak, Ronald M., ed. 1999. Walker's Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press; Paddle, Robert N. 2000. The Last Tasmanian Tiger. Cambridge: Cambridge University Press; Rounsevell, David E., and S. J. Smith. 1982. "Recent Alleged Sightings of the Thylacine (Marsupialia, thylacinidae) in Tasmania." In Carnivorous Marsupials, edited by Michael Archer, pp. 233-236. Mosman: Royal Zoological Society of New South Wales; Smith, Malcolm. 1982. "Review of the Thylacine (Marsupialia, Thylacinidae)." In Carnivorous Marsupials, edited by Michael Archer, pp. 237-253. Mosman: Royal Zoological Society of New South Wales.

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