Koalas Overrunning Australia Island "Ark"

Bijal Trivedi
National Geographic News

May 10, 2002

On Kangaroo Island, a rugged eco-tourism paradise 30 minutes by
air southwest of Adelaide, the koala is eating its way out of house
and home and eucalyptus tree. Wildlife officials are sterilizing and
exporting the fuzzy little marsupials to the mainland, but not
everybody thinks the population-control program makes ecological
sense.

"Koalas are not the root but only a small part of the problem," maintains Deborah Tabart, executive director of the Australian Koala Foundation, a private research and conservation organization. She considers the government's random sterilization a "knee-jerk" response that disrupts the koala community.

Koalas, declared an endangered species by the U.S. Fish and Wildlife Service two years ago, are anything but threatened on the 737-square-mile island where they strip the manna gum eucalyptus trees they favor, eventually killing the trees. The government has sterilized about 3,400 adult koalas since 1997 and shipped out over 1,000.

"When we remove the koalas, the trees recovered. It is a clear indication that the koalas are the problem," says Keith Twyford, Kangaroo Island regional manager for National Parks and Wildlife South Australia.

The island is home to plant and animal species found nowhere else, but the koala wasn't always among them. When the koala faced extinction because of over-hunting for its fur, the government introduced about 18 adult koalas from French Island in Victoria in the early 1920s.

"They saw Kangaroo Island as an Ark where the animals could live free from the pressures of development," Twyford explains.

With no natural enemies, the koalas thrived, spending up to 20 hours a day snoozing in the eucalyptus trees and the rest of the time eating them. A 2000-2001 survey estimated about 27,000 koalas on the island. The koala foundation believes the total number in the country is around 100,000, but other estimates go as high as 400,000.

Elsewhere in the nation, koala populations are declining, threatened by wood-chip production, foxes, dogs, automobiles and urbanization. But the solution is not as simple as moving koalas from where there are too many to where there are too few. Several sub-species are involved, and the Kangaroo Island variety is larger than those found in Queensland and New South Wales.

On the mainland, koalas suffer from chlamydia, a sexually transmitted disease causing infertility in females. Scientists suspect it has been controlling koala populations naturally for years. Adding more koalas would only put more stress on an already diminishing habitat.

Few koalas live outside Australia, but the U.S. government designated the animal as endangered in response to a petition filed by animal-protection groups. The Australian government, which bans hunting and commercial use of koalas, sees no scientific evidence that it is likely to become endangered anytime soon.

A national conservation policy dictates how individual states manage their koala populations, but South Australia's decision to sterilize sparked public outcry and a heated media debate. Politics, economics and the "Bambi factor" stirred as much discussion as the science.

Koalas in the wild and on the toy shelf are just too cute. Wildlife experts call them "charismatic megafauna" that bring about 140,000 tourists a year to Kangaroo Island.

"People come to the island to see the koalas and culling the population could damage the economy of the island and its international reputation as a haven for wildlife," admits Twyford. While culling the koala the way deer are sometimes managed in the United States is not illegal, it is "not an appropriate management option."

Instead, the government spends about U.S. $160 per koala in the sterilization program in round-ups each year between January and April. Using a noose tied to a long pole, wildlife officers slip a loop around the animal's neck and steer it down the tree. Sterilization of both males and females is done in a veterinary clinic. They are back in their trees the same day.

So far the sterilization program has had no impact on tourism, reports the Australian Tourist Commission, but the koala foundation has other concerns.

"Just because there are large numbers of these animals in some places does not mean that everything is OK," Tabart says.

Inbreeding on Kangaroo Island for nearly 80 years has produced genetic defects. Random sterilization might eliminate the fittest, Tabart warns. Better, she contends, to plant more trees.

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