SYDNEY - On the outskirts of Sydney, a stretch of native bushland is home to a colony of about 500 koalas which - unlike much of Australia's koala population - has been thriving and growing in numbers.

It is believed to be the last healthy koala colony in Sydney, where numbers have plunged since European settlement due to hunting, land-clearing and urban development. In recent years, a chlamydia epidemic has added to concerns that the iconic native animal may be facing the threat of extinction.