塔斯馬尼亞惡魔的死亡之謎英語美文
Starting in the late 1990s Tasmanian wildlife authorities began receiving unusual reports: Some of the island"s Tasmanian devils were spied with their faces marred by ulcerated sores.
Small and furry, the carnivores are known for their unearthly howl and cranky temperament. They are also well loved as a species unique to Tasmania, an island outpost calved from mainland Australia.
But what was initially a bit of a scientific curiosity soon became a potential catastrophe. The results of the first investigative survey revealed that tens of thousands of Tasmanian devils had died from a disease now known as Devil Facial Tumor Disease.
Alistair Scott is a project leader for the devil disorder program at Tasmania"s Department of Primary Industries, Water, and Environment. He says that initial survey revealed that the disease was running rampant through the eastern half of Tasmania.
"Mapping and monitoring showed it was across 65 percent of the state," Scott said.
"The maximum population estimate [before the disease struck] was between 130,000 and 150,000. So from that, we believe we"ve lost up to 75,000. This has had a major impact on the devil population.""
Devil Facial Tumour Disease causes cancers to appear first in and around the mouth before spreading down the neck and, sometimes, into the rest of the body. Both male and female adults are more commonly affected than juveniles.
Sick devils also become emaciated, because the tumors interfere with eating, and many mothers lose their young.
The animals can die within six months of the appearance of the first sores, and in some areas whole populations have been wiped out within 18 months.
A special Tasmanian devil-dedicated laboratory has been set up in the northern town of Launceston, where scientists are desperately trying to work out what causes the disease and how it is transmitted.
"At the moment the scientists are working on the hypothesis that the disease is physically transferred," Scott explained.
"That has only been recorded once before in the animal world, and that was a venereally transmitted canine cancer. It"s a unique disease we"re dealing with.
Once it"s detected—and even then, that is only visually—the animal is on death row. They are dead three to six months later."
The team is working on the disease"s chromosome structure and has just identified the karyotype. (Karyotypes are pictures of cellular chromosomes that are used to check for abnormalities.)
The researchers say they have also been able to develop tumor cells in the lab, enabling them to run tests without actual tumors.
A diagnostic test and, ultimately, a vaccine are the scientific team"s main aims. But while the scientists race to learn more about the disease, the Tasmanian government is trying to stop the disease from spreading further.
To stop infected animals from moving in, trapping lines are being set in the north of Tasmania, an area that so far appears to be disease free. The government is also considering whether to list the species as threatened under Australia"s threatened-species laws. Threatened status would give the devils protection from other perils, such as habitat destruction caused by water pollution or land development.
The move would also require the government to draw up a plan for recovery of the species. Such a plan would focus on managing the disease where it already exists and on preventing it from affecting more animals.
The disease "is having a very serious impact on the wild population, but at this stage we don"t believe that the species is headed for extinction," Scott said.
"In the areas where it has been present but [where] there"s only a low level population, it has had a major impact. One of the problems is that the devil is nocturnal, and many people never see it in the wild. So it"s very difficult to pick up changes in the population.""
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