Harriet the Australian tortoise turns 175

A tortoise in an Australian zoo has celebrated a 175th birthday, which some say makes it the oldest known animal on the plant.

A tortoise that was hatched in the Galapagos Islands when Charles Darwin was developing his theory of evolution has turned 175.

Harriet is recognized as the world's oldest known animal.

"She would definitely be the oldest living animal on Earth. ... I can't see why she shouldn't live till 200," says Steve Irwin, owner of the zoo north of Brisbane, Australia, where Harriet lives.

The Guinness Book of World Records has recognized her as the world's oldest living chelonian (turtle or tortoise).

It may have been Darwin who brought Harriet back from an exploration trip – there is dispute on that point – to start a long life of captivity.

For more than a century, the giant Galapagos land tortoise was originally thought to be a male, so was called Harry.

Harriet has lived at the Brisbane-area zoo for 17 years. Zoo staff marked her approximate birthday on Tuesday with such treats as a pink hibiscus flower cake.

Zoo officials say she shows no sign of physical decline, perhaps because of a strict fitness regimen. In the morning, she goes outside and warms up. When she's had enough sun, she retreats to the shade.