Are Kangaroo Island's koalas under threat?

Are Kangaroo Island's koalas under threat?

A retrovirus is sweeping through the koala population and experts fear their days are numbered
A wild koala on Kangaroo Island.

South Australia’s Kangaroo Island takes its name from the mobs of kangaroos that graze its dense bush.

Koalas were introduced in the 1920s, and flourished so spectacularly that at one point it looked like they might overrun the 4,405-square-kilometer island.

But now the koala colony could be under threat. An AIDS-like retrovirus has made its way from the mainland and been detected on the island.

Some expert warnings are dire: it could eventually wipe out the population.

The Koala Research Network told a recent Senate inquiry the disease is spreading through the island like wildfire.

An initial population analysis discovered no infections on the island in 2004 -- but the rate of infection has quickly jumped to 15 percent in 2006 and then again to more than 36 percent in 2009.

“This virus may be as devastating to koalas as the facial tumor disease was to Tasmanian Devils,” says Dr. Jon Hanger, the koala veterinary specialist who discovered the retrovirus.

The virus is linked a range of diseases in koalas including lymphoma, leukemia, malignant tumors and immune deficiency disorders. 

“We don't exactly know how the virus is spreading, or how quickly,” says Dr. Hanger. “But if our suspicions about disease association are correct, then the potential impacts on Kangaroo Island koalas are serious.”

Symptoms exist, but population abundant, says government

The South Australian Government maintains the retrovirus is not a threat.

“There is no evidence to suggest that the koala population on Kangaroo Island will become extinct from the retrovirus,” a Department of Environment and Natural Resources spokesperson said. 

“Although the koala retrovirus is present in some koalas on Kangaroo Island, no physical symptoms from the disease have been detected.”

In fact, the department says it remains necessary to actively manage the island’s “over-abundant” population for the sake of the native habitat and the koalas themselves.

More than a decade ago, the state government introduced a sterilization program to get koala numbers under control. Slightly more than 10,000 were sterilized and 3,800 were relocated to the state’s southeast.

As a result, the overall population size has dropped from an estimated 27,000 koalas in 2001 to 13,000 in 2010.

And that's a good thing, maintains the environment department.

“The symptoms and signs of the retrovirus tend to appear when populations are put under stress, and the stresses on the koala population on Kangaroo Island are reducing with the declining population,” the department spokesperson said.

Koala habitat

koalaA koala and cub in the Hanson Bay Wildlife Sanctuary.The island continues to be a top tourist destination, said the South Australian Tourism Commission (SATC).

It is estimated that about 190,000 visitors make their way to the island each year, funneling millions of dollars into the local economy. 

Apart from koalas, the island is home to a host of native flora and animals including kangaroos, Tammar wallabies, possums, sea lions, fur seals and echidnas.

But it’s the elusive koala that tends to be the big draw for wildlife spotters. Often difficult to sight on the mainland, koalas are easy to find on the island, in part, because of strict quarantine regulations that prevent predators, such as foxes and rabbits, from accessing the island.

“The island [is] a wildlife sanctuary,” said an SATC spokesperson. “One third of the island is conservation or national park and there are more than 2,200 square kilometers of native vegetation, making it the perfect habitat for koalas.”

That precious population still has Dr. Hanger worried -- even though no disease linked to the retrovirus has yet formed in the island’s koalas.

“It is possible that it takes years for disease impacts to occur,” Dr. Hanger says.

“They are also less genetically diverse than mainland koalas, so hypothetically may be even more susceptible.”

Kangaroo Island's koalas

The 3,844-hectare Hanson Bay Wildlife Sanctuary, situated on the island’s southwest coast, includes hot spot “Koala Avenue." Nocturnal walks with a tour guide are also offered through the site’s 100-hectare fenced and feral-free zone. An original farmhouse has been converted into an upmarket hostel, alongside six self-contained cabins.

Hanson Bay Wildlife Sanctuary, +61 (0)8 8559 7344,

Popular sites also include Flinders Chase National Park and Seal Bay Conservation Park. But locals advise following a few tips: move slowly and quietly, observe from a distance, don’t feed the animals and stay on the trail.

Tourism Kangaroo Island, +61 (0)8 8553 1185,

Getting to Kangaroo Island

Kangaroo Island"The Remarkables" on Kangaroo Island.Kangaroo Island SeaLink operates two passenger ferries between Cape Jervis and Penneshaw. There are four departures daily, with additional services during peak times. Bookings are necessary on 13 13 01 (in Australia) or

Regional Express (REX) operates the 30-minute flight from Adelaide to Kingscote Airport (KGC), which is located 13 kilometers from the Island's capital, Kingscote.  Reservations on 13 17 13 or +61 (0)8 8553 2938 or