Koalas in the Blue Mountains World Heritage area continue to provide surprising hope for the endangered species' survival. Science for Wildlife researcher Dr Kellie Leigh says that less than a decade ago the general view was that there weren't many koalas in the Blue Mountains and, if they were around, they were at low density and not of great significance. But her project, running since 2014, has found koalas breaking all the rules, living above 800 metres, on sandstone country where soils are poor and the size of the gum trees is limited. Plus, the koalas are free of chlamydia, which has ravaged other populations, and they've been found to have the highest genetic diversity in the nation. That makes them pretty special, even with the big losses during the Black Summer fires.