Nightfall comes early under the dense cloak of the rainforest canopy and Ollie Scully – boots off and barefoot – is wading through the cool water with his torch scouring the rocky bottom of a shallow creek.

We are at an undisclosed spot in the hinterland of Queensland’s Sunshine Coast. With leeches and trip hazards aplenty, the search has been on for hours.

“This will not be for the want of trying,” he shouts.

Ecologist and conservationist Ollie Scully searches for spiny crayfish (Euastacus). When he found his first one, he was ‘instantly obsessed’. Photograph: Krystle Wright/The Guardian

And then there it is, picked out in the torch beam – a spiny crayfish. Just hanging out – this relic of Australia’s ancient past and resident of the continent’s freshwater habitats for tens of millions of years.

“It’s a Conondale … one of the giants,” Scully says.

This is a juvenile, about 15cm long. As Scully places her down, she rears up her claws in a defensive display. She looks other-worldly. Her right claw is in the process of growing back.

“Most likely she had a run-in with an eel,” says Scully, only minutes after a metre-long eel – a crayfish predator – glided past his legs. “They can drop their claws in self-defence.”

A spotlight trained on a female dwarf spiny crayfish. Photograph: Krystle Wright/The Guardian

The Conondale spiny crayfish – one of 52 known species of spiny crayfish unique to Australia – is endangered.

In 2019 only three appeared on the country’s threatened species list. Now there are 36, with more heading for the list.

“Most Australians are not aware of them,” says Dr Nick Whiterod, an ecologist and crayfish expert at the Coorong Lower Lakes and Murray Mouth (CLLMM) Research Centre and Adelaide University.

“People could be water skiing or whatever and have no idea there might be thousands of crayfish under their feet.

“But these guys are really threatened and we’ve got concerns about their future.”

Rapid change

Whiterod has been studying the “spinies” and their genetics for decades. He believes a coordinated national effort is needed to save them.

“They split off from the marine crayfish and then from the northern hemisphere crayfish about 100m years ago,” he says.

“So they’ve been here a long time and they’ve withstood everything Australia has thrown at them.

Experts say a coordinated national effort is needed to save the spiny crayfish. Photograph: Krystle Wright/The Guardian

“But the rate of change is escalating in terms of climate and fire and what humans have done to alter their habitat in the last 200 years. A lot of the species are not well adapted to cope with rapid change.”

Spinies can live for decades – some maybe 50 years – and are found in pockets across a massive range, from the far north of Queensland to South Australia, from rainforests to alpine bogs.

They grow by regularly moulting their hard shell and have to survive at least five years before they can reproduce.

Across the species, they face threats from feral pigs and foxes, poachers, and the degradation of the shady creeks and banks that many of the species call home.

But Whiterod says their main threat is climate change, which is raising the temperature of the water, drying out the creeks and making their habitat more susceptible to bushfires.

“This is all conspiring to make them a highly threatened genus,” he says. “We’re assessing all the species and for all of them there’s worrying signs for their extinction risk.”

The 2019-2020 bushfires scorched the habitat for an estimated 40% of the species.

Whiterod says fire itself can raise water temperatures that can kill crayfish. It also strips shade from the overhead canopy, causing water temperatures to rise. The surrounding scorched undergrowth can’t hold on to the sediments and when it rains, the soils and ash then flush into creeks.

“They can’t physiologically cope and they will just cook,” says Whiterod.

Climate change is raising the water temperature, drying out creeks and making the habitat of the spiny crayfish more susceptible to bushfires. Photograph: Krystle Wright/The Guardian

WWF-Australia has funded scientific work that has led to eight spinies being listed as critically endangered.

The charity’s conservation scientist, Dr Stuart Blanch, says spinies are “the canaries in the coalmine for many species living in the delicate ecosystems of our mountain streams”.

“The survival of spinies depends on transitioning away from fossil fuels and stabilising global temperature increases to no more than 1.5C,” he says.

‘Instantly obsessed’

Scully first got interested in spinies when he was out looking for threatened frogs “and then 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 start studying the species “get hooked” in the same way.

Ecologist Ollie Scully says he first got interested in spinies when he was looking for threatened frogs ‘and then this huge rock just moved’. Photograph: Krystle Wright/The Guardian

“They’re not the obvious thing to get obsessed about – people usually go for the furry things – but they’re incredibly captivating. They get under your skin.”

One of those hooked by the spinies is Rob McCormack. He first got interested in the early 1980s when he was farming yabbies – another freshwater crayfish in a different group than the spinies, whose scientific name is Euastacus.

“Most people know the yabby, but the spinies are a different kettle of fish,” says McCormack.

“I was looking at all these weird and wonderful species, and they were mainly the Euastacus. We were cultivating them and that gave me an insight. Then when I sold the business, I started investigating them.

“They’re incredibly long-lived – I could show my children a crayfish in a pool and they could bring their children back and show them the same crayfish in the same pool.

‘Most people know the yabby, but the spinies are a different kettle of fish, researcher Rob McCormack says. Photograph: Krystle Wright/The Guardian

McCormack has been investigating the spinies full-time for 20 years, helping identify new species and map their whereabouts. He’s now a research associate with the Carnegie Museum of Natural History in Pennsylvania.

“They’re the engines that drive the whole river system,” he says. “They’re not a species people should be catching and eating, or putting in a fish tank.

“For one to reach maturity and replace an adult, it’s maybe a 1,000 to 1 chance. So these are the food sources for all the other animals to live on. Healthy crayfish populations mean healthy streams.”

Both Whiterod and McCormack have witnessed major die-offs of spinies, where sharp drought and then fire have killed off whole populations. Decades-old spinies gone in a flash.

“Given enough time, they should recover,” he says. “But if that becomes a regular theme from climate change, then these populations are never going to recover.”