A brave little koala has survived a perilous 16-kilometre (10-mile) journey clinging to the axle of a four-wheel-drive.

The marsupial is believed to have crawled into the car's wheelwell unbeknownst to the driver, who then started driving through the winding terrain of the Adelaide Hills in South Australia. Other drivers had flagged him, but he didn't notice anything amiss until he stopped and heard her crying.

He called Fauna Rescue South Australia's Koala Rescue Hotline, who had to call the fire brigade to take the car's wheel off.

"I could see her behind the wheel but I had no idea, until we got the wheel off, whether she had broken limbs or what the story was," said Fauna Rescue's Jane Brister.

"I could smell her burnt fur. It would have been hot in there."

The six-year-old koala, named Kelli after one of the firefighters who rescued her, was taken back to Fauna Rescue to be treated. There, she was found to be in surprisingly good health, with only minor injuries.

But it wasn't an entirely happy ending. Kelli was found to be lactating, and the fur on her back was knotted from the grip of a joey (a koala baby). Sadly, the joey wasn't found.

"I searched that night and the next day, and the next, but I never found it," Brister said. "After everything she went through, she lost her joey as well."

Koala population sizes are hard to gauge, but the species is listed as vulnerable on the Red List of Threatened Species, with an estimated decline of 28 percent.

Its main threats are habitat destruction and modification, with dogs and cars posing a high risk, as well as drought, disease and bushfires.

After a few days under observation, Kelli was tagged and released back into the wild.

If you find a koala in South Australia who needs help, the 24-hour hotline is 1300-KOALAS. Rescue services for the rest of Australia can be found on the RSPCA website.