Koalas are getting harder to find. Scientists in Australia are on a quest to uncover a hidden population.

“Something definitely likes going up this tree.”Marsh peered up at the canopy of eucalyptus leaves, hoping to catch a glimpse of the animal she and a small team had spent weeks searching for — a koala.But one of Australia’s most iconic animals is getting harder to find.Two years ago, when bush fires supercharged by climate change killed or displaced an estimated 3 billion animals, thousands of koalas were among the dead. Although adapted to Australia’s frequent dry spells, the animals couldn’t cope with a climate-change-fueled drought in 2018 and 2019 that saw dehydrated koalas literally dropping from trees.Then came the Black Summer bush fires, which burned more than 20 percent of Australia’s forests.Marsh, a research fellow at Australian National University in Canberra, watched as the blaze roared to within a few hundred yards of her house. Researchers would then listen to any hits to confirm that they were koalas and not a park ranger driving past in a pickup truck.“I’ve heard many, many koalas, so I feel confident,” Marsh said when asked about her ability to identify the mating calls.After examining the map, she and an ANU student research assistant went to survey the trees at several sites while James Skewes took another student to set up audio recorders.Skewes, an ecologist accustomed to the bush, powered his pickup truck over fallen logs and streams until his GPS device pinged. Now they were preparing to go spotlighting, the process of methodically shining flashlights into trees at night in the hope of seeing the reflection of an animal’s eyes.“Can someone please spot a koala,” Marsh said in half-serious desperation as she and Skewes divided up the flashlights.