Australia’s ancient spiny crayfish are now critically endangered, with the number of threatened species rocketing from just three in 2019 to 36 today — and more still heading for the list. The dramatic escalation in their conservation status has been driven largely by climate change, which scientists say is overwhelming creatures that have survived on the continent for 100 million years. WWF-Australia has funded scientific work that has led to eight species being listed as critically endangered, giving them stronger legal protection under federal law.
Discovery of a relic
Nightfall comes early under the dense cloak of the rainforest canopy, and Ollie Scully – boots off and barefoot – is wading through cool water with his torch scouring the rocky bottom of a shallow creek. The search has been on for hours at an undisclosed spot in the hinterland of Queensland’s Sunshine Coast, with leeches and trip hazards aplenty. “This will not be for the want of trying,” he shouts. Then, picked out in the torch beam, there it is: a spiny crayfish, a relic of Australia’s ancient past that has inhabited the continent’s freshwater habitats for tens of millions of years. “It’s a Conondale … one of the giants,” Scully says.
The juvenile, about 15cm long, rears up her claws in a defensive display when placed down. Her right claw is 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.”
The Conondale spiny crayfish (Euastacus hystricosus) is one of 52 known species of spiny crayfish unique to Australia. It is Queensland’s largest freshwater invertebrate, capable of living for over 50 years and reaching up to 2kg in weight. Adult specimens are dark green with red, orange or yellow claw tips and can grow to 15.6cm in carapace length. Some species are known to make a “hissing” sound. They are largely nocturnal and inhabit large burrows in creek beds within the Conondale and Blackall ranges and the Bellthorpe Mountains.
Spiny crayfish belong to the genus Euastacus, which is endemic to the southeastern Australian mainland and part of the family Parastacidae, a group of freshwater crayfish found exclusively in the Southern Hemisphere. They split off from marine crayfish and from northern hemisphere crayfish about 100 million years ago. Their evolutionary history is deeply intertwined with Australia’s changing climate and landscape; many species became isolated on “mountain top islands” since the Miocene epoch – over 5 million years ago – leading to a high degree of endemism, with some species restricted to a single river or creek catchment. The Fitzroy Falls Spiny Crayfish (Euastacus dharawalus), for example, is found only within a 12km stretch of creek in the Southern Highlands of New South Wales. Recent molecular taxonomy studies, led by Professor Chris Austin and Dr Nick Whiterod, have revealed significant cryptic diversity, potentially identifying as many as 26 new species – a 50% increase in known species within the genus. Genetic studies suggest there could be as many as 79 species.
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.” Dr Nick Whiterod, an ecologist and crayfish expert at the Coorong Lower Lakes and Murray Mouth (CLLMM) Research Centre and Adelaide University, says most scientists who start studying the species “get hooked” in the same way. “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 is Rob McCormack, who first became interested in the early 1980s when he was farming yabbies – another freshwater crayfish in a different group. “Most people know the yabby, but the spinies are a different kettle of fish,” says McCormack, now a research associate with the Carnegie Museum of Natural History in Pennsylvania and leader of the privately funded Australian Crayfish Project. He has been investigating spinies full-time for 20 years, helping identify new species and map their whereabouts. “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.” Spinies grow by regularly moulting their hard shell and have to survive at least five years before they can reproduce. Some species may live 50 years or more.
McCormack emphasises their ecological importance: “They’re the engines that drive the whole river system. 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.”
The gathering threats
Across the species, spinies face threats from feral pigs and foxes, poachers, and the degradation of the shady creeks and banks that many call home. The construction of reservoirs has divided populations, and the loss of cooling vegetation along water edges makes it difficult for crayfish to cope with stress events like drought. Poaching also risks the introduction of diseases such as crayfish plague. In one known incident, a pesticide spill in Jamison Creek, New South Wales, caused a mass kill of the Giant Spiny Crayfish (Euastacus spinifer).
But the primary threat, according to Dr Whiterod, is climate change. “This is all conspiring to make them a highly threatened genus,” he says. Rising water temperatures, drying creeks, and an increased frequency and intensity of bushfires are severely impacting their habitats. Unlike the more widespread Cherax species, spiny crayfish cannot survive the drying of their habitats. Some species have lethal temperatures around 23°C.
The 2019-2020 bushfires scorched the habitat for an estimated 40% of Euastacus species. Whiterod explains that fire itself can raise water temperatures enough to kill crayfish. It also strips shade from the overhead canopy, causing water temperatures to rise further. The surrounding scorched undergrowth cannot hold on to the sediments, and when it rains, soils and ash flush into creeks. “They can’t physiologically cope and they will just cook,” says Whiterod. Post-fire runoff carries ash and sediment that can clog gills, reduce oxygen levels, and create toxic conditions. Research indicates that these impacts on water quality can persist for years. Both Whiterod and McCormack have witnessed major die-offs of spinies, where sharp drought followed by fire killed whole populations. “Given enough time, they should recover,” says McCormack. “But if that becomes a regular theme from climate change, then these populations are never going to recover.”
Whiterod notes that the rate of change is escalating in terms of climate, 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.” He has been studying the genetics of spinies for decades and believes a coordinated national effort is needed to save them. “Most Australians are not aware of them. 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.”
A race to save them
WWF-Australia’s conservation scientist, Dr Stuart Blanch, describes spiny crayfish as “the canaries in the coalmine for many species living in the delicate ecosystems of our mountain streams.” He says their survival depends on transitioning away from fossil fuels and stabilising global temperature increases to no more than 1.5°C.
A significant milestone was reached in September 2023, when 15 spiny crayfish species were added to Australia’s list of at-risk fauna under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). This brought the number of threatened Euastacus species under the Act to nearly 35%. A further 17 species are under evaluation for listing. The Conondale spiny crayfish itself was added to the threatened species list for the first time in September 2024.
In response to the 2019-2020 bushfires, the federally funded “Saving the Spinys” project was launched to conserve 22 priority Euastacus species. Its objectives include determining range limits, identifying critical populations, resolving taxonomic uncertainties, and exploring conservation translocations. In New South Wales, the “Totally Cray Cray” project is focused on improving the trajectory of the Fitzroy Falls Spiny Crayfish through habitat improvement and pest removal. Researchers from organisations including the CLLMM Research Centre, the Australian Crayfish Project, the University of the Sunshine Coast, Griffith University, the University of Wollongong, and Charles Sturt University are all involved in ongoing work.
Whiterod stresses the urgent need for more research into the life history of many species, particularly burrowing species, to inform effective conservation assessments. “We’re assessing all the species and for all of them there’s worrying signs for their extinction risk,” he says. The Euastacus genus is now considered one of the most threatened genera of freshwater crayfish globally, and Australia’s freshwater crayfish fauna as a whole is the most endangered in the world.
