Night falls early under the rainforest canopy, and Ollie Scully - barefoot, torch in hand - is wading through a shallow creek in an undisclosed spot in Queensland’s Sunshine Coast hinterland. Leeches are plentiful, trip hazards are everywhere, and the search has been going on for hours. Then, finally, a torch beam catches it: a spiny crayfish, just hanging out like the ancient relic it is, having called Australia’s freshwater habitats home for tens of millions of years.

Scully identifies it as a juvenile Conondale spiny crayfish, about 15cm long. When he puts her down, she rears up her claws in a defensive display. Her right claw is regrowing - likely lost in a run-in with an eel, Scully explains, noting that a metre-long eel, a known crayfish predator, recently glided past his legs. “They can drop their claws in self-defence,” he says.

The Conondale spiny crayfish is one of 52 known species of spiny crayfish unique to Australia, and it’s endangered. In 2019, only three species were on the country’s threatened species list. Now there are 36, with more heading that way. “Most Australians are not aware of them,” says Dr. Nick Whiterod, an ecologist and crayfish expert at the Coorong Lower Lakes and Murray Mouth Research Centre and Adelaide University. “People could be water skiing and have no idea there might be thousands of crayfish under their feet. But these guys are really threatened.”

Whiterod has been studying the “spinies” and their genetics for decades. He says they split from marine crayfish and northern hemisphere crayfish about 100 million years ago. “They’ve withstood everything Australia has thrown at them. But the rate of change is escalating in terms of climate and fire and what humans have done in the last 200 years.”

Spinies can live for decades - some maybe 50 years - and are found from far north Queensland to South Australia, from rainforests to alpine bogs. They moult their hard shells regularly and must survive at least five years before reproducing. Threats include feral pigs, foxes, poachers, and degraded creeks. But the main threat is climate change, which is warming waters, drying creeks, and making habitats more vulnerable to bushfires. The 2019-2020 bushfires scorched habitat for an estimated 40% of species. Fire raises water temperatures that can kill crayfish, strips shade from the canopy, and causes sediment and ash to flush into creeks. “They can’t physiologically cope and they will just cook,” says Whiterod.

WWF-Australia has funded work that led to eight spiny species being listed as critically endangered. The charity’s conservation scientist, Dr. Stuart Blanch, calls spinies “the canaries in the coalmine for many species living in the delicate ecosystems of our mountain streams.” He adds, “Their survival depends on transitioning away from fossil fuels and stabilising global temperature increases to no more than 1.5C.”

Scully first got interested in spinies while looking for threatened frogs, when “this huge rock just moved. It was this enormous crayfish. I’d never seen anything like it. I was instantly obsessed.” Whiterod says most scientists who study them get hooked similarly. “They’re not the obvious thing to get obsessed about - people usually go for the furry things - but they’re incredibly captivating.”

Rob McCormack, another spiny enthusiast, started investigating them in the early 1980s while farming yabbies. “Most people know the yabby, but the spinies are a different kettle of fish,” he says. Now a research associate with the Carnegie Museum of Natural History in Pennsylvania, McCormack has spent 20 years helping identify new species and map their locations. “They’re the engines that drive the whole river system,” he says. “Healthy crayfish populations mean healthy streams.”

Both Whiterod and McCormack have witnessed major die-offs, where sharp drought and then fire have killed whole populations - decades-old spinies gone in a flash. “Given enough time, they should recover,” McCormack says. “But if that becomes a regular theme from climate change, then these populations are never going to recover.”