When we think of the effects of climate change it’s easy to focus on rising sea levels – but what about the changes happening much higher up? At Mount Hotham in Victoria a unique creature spends months under the snow: Australia’s only hibernating marsupial, the mountain pygmy possum. This tiny animal was once thought extinct. Now, zoos and ski-resorts are doing everything they can to keep it alive, but it faces a changing climate, which may create insurmountable challenges