Kangaroos

In Australia, Joy and Mark uncover the reproductive secrets of some of the strangest mammals on Earth - the pouch-wearing marsupials. Thanks to their bizarre way of reproducing, kangaroos thrive in one of the most unpredictable, drought-prone environments on Earth - the Australian Outback. In Queensland's eucalyptus forests, he sees how tree-living marsupials - koalas - have mastered gravity-defying sex.