When I was a teenager, I dreamt of being a marine biologist. Back then, the biggest threat to the Great Barrier Reef was a hungry starfish. I thought climate change was the cold front due the day after tomorrow; and extinction only happened in history books, when something tasty and easily caught, like the dodo, got its Darwinian just deserts.
But a terrifying experience on my first “real” scuba dive on a rocky reef in the open ocean changed everything. I altered course and found my scientific niche in a chemistry lab. For the most part, I’ve been happy there – until my “lobster epiphany” a few years ago.
Sadly, in the intervening four decades, things have changed for the worse. Everywhere, habitat is under threat from our rapacious greed. Climate change has us lurching between catastrophic bushfires and once-in-a-century floods that come twice a year. Worst of all, Australia punches far above its weight in extinction.
Studying ecology is no less important today, but sometimes it seems like we’re training medics for a war zone. They can patch up the injured, but can’t stop the destruction and killing. The news is always bad.
Well, almost always. Wouldn’t it be wonderful if, every now and again, we learnt an extinct species is not extinct after all?
So, here is some good news. Next time you drive the Lyell Highway and cross the Bradshaw Bridge spanning Lake Burbury, smile. Smile in the knowledge that an animal thought extinct still survives there. Smile because the short-tailed rain crayfish (Ombrastacoides parvicaudatus) is not extinct.
During lockdown, while the rest of the world was trapped indoors, a dedicated team of invertebrate biologists was out braving the sort of wild weather only the west coast can serve up, searching for this enigmatic little animal.
The team was led by Drs Alastair Richardson and Niall Doran. Richardson left England and joined the University of Tasmania 50 years ago. He was excited to be in “a land where a zoologist could run wild”. On arrival, he knew nothing about freshwater crayfish but soon became fascinated with the amazing variety of these animals in Tasmania. There are at least 33 species, with a few more probably still waiting to be discovered. They range from little terrestrial crayfish that live in holes in the ground to the enormous “lobster”, the stream-dwelling giant freshwater crayfish (Astacopsis gouldi).
Doran was once a student of Richardson, but now they work together for the Bookend Trust (bookendtrust.com) a not-for-profit organisation dedicated to inspiring students and their communities to engage positively with the environment and make the world a better place.
“Crayfish are a lot of fun to work with,” said Doran. “They’re beautiful animals. They’re charismatic and really entertaining.”
Richardson and Doran have studied freshwater crayfish all over Tasmania, but in the west there’s a very special group, the rain crayfish. These small burrowing crayfish are remarkable. Their closest relatives are not found on mainland Australia, but in New Zealand, South America and Madagascar. Like our deciduous beech (Nothofagus gunnii), they are living relics of Gondwana.
“They’re a great evolutionary story,” said Doran.
Rain crayfish are endemic to western Tasmania. “From an ecological point of view, they’re really important,” Richardson said. They dig deep burrows in the peaty soils of buttongrass plains and swamps, which are by their very nature infertile, waterlogged and poor in oxygen. The burrows drain and aerate the peat, encouraging the growth of vegetation.”
The short-tailed rain crayfish was known from just six specimens collected in the 1970s and ‘80s in an area of only 10 square kilometres in the upper King River valley. When the Crotty dam was completed in 1991, this tiny area – the short-tailed rain crayfish’s only known habitat – was drowned by the rising waters of Lake Burbury.
“These are terrestrial crayfish,” said Doran. “They don’t like being flooded. The question was, did they survive? Are they still there?”
There was only one way to find out. With the support of Entura, Hydro Tasmania’s consulting arm, they launched their boat and set out to search the shore of the lake closest to where the short-tailed rain crayfish was last seen.
“There’s an old saying,” said Doran, “that the worst day in the field is still better than the best day in the office.”
Richardson added, “It’s not every day you get to rediscover a species we thought extinct.”
Richardson recounted that first day of the search. “We hopped out of the boat, more in hope than expectation. We started looking in the steep rocky creeks that run down off the mountain into the lake. They’re hard to get into and it was raining most of the time. We scrambled up, looking along the edges, in pools and under and between the rocks. And lo and behold there in a little pool was a crayfish! It was definitely a rain crayfish – it was reddish and had orange bases to the legs. We took it back down to the boat and I started doing measurements. I was thinking, could this be it? The first specimen of the short-tailed rain crayfish collected since 1980?”
With a laugh, Doran added, “Suddenly, that’s it. We’ve got it! I hate to say it was easy, but that one was.”
But it wasn’t as simple as finding one crayfish. They came back and undertook an extensive field survey. They searched all the other gullies, like the one they found it in, which were suitable habitat. They also needed to investigate other areas where the short-tailed rain crayfish might meet other species, to determine its geographic range. And that meant a lot of hard, dirty work.
“Sadly, there’s no way to entice a crayfish out of its burrow,” said Richardson. “Anything you do near the entrance only encourages it to go to the bottom. And that means digging. Digging in peat, digging in clay, digging in slushy mud. That can take anything from five minutes to five hours.”
Because of western Tasmania’s geology, the peat where the crayfish live often overlies smashed up glacial rock, usually quartzite – and it’s sharp.
When digging, the biologists don’t wear gloves, so they can feel for crayfish in the tunnels ahead to avoid harming them. Richardson said, “When you dig down, you find the crayfish has its refuge under some broken bit of quartzite rock that proceeds to rip your fingers apart as you try to get under there. It’s a wonderful business. Everyone should try it!”
Watching Richardson and Doran digging for crayfish reminded me of the dogged prospectors who scoured these same western ranges in search of precious minerals. “It’s challenging,” Doran agreed. “It’s difficult. It’s muddy work, it’s hard work. It rips your hands – but you get ‘crayfish fever’ and you just keep going. You want to find that little guy at the end of the burrow.”
“Another problem was this animal could be really rare,” said Richardson. “So, we didn’t want to take live animals from the field and reduce a potentially very small population.”
To make sure they’d found the right species, the field work needed to be backed up with DNA analysis. Fortunately, these days you can take non-lethal DNA samples. So, they were able to release these specimens without decreasing the population.
The survey found short-tailed rain crayfish in good numbers at several sites, including breeding females with clutches of eggs under their tails. “This was really important and exciting,” said Richardson. “It means the population is not just clinging on, it’s actually reproducing.”
Often during surveys, there are serendipitous discoveries. The team was able to fill in gaps on the map for several other species of rain crayfish. “In one case,” said Richardson, “we found an animal on the eastern side of the lake that was only ever known from a very restricted distribution some 20 km away.”
. . .
We are lucky enough in Tasmania to still have the opportunity to conserve things in the wild. Not everywhere in the world does. With a bit of will, forethought and planning, threatened species can be conserved.
“It’s great to be able to take part in an exercise that brings one of these species back to life, as it were,” Richardson said.
“We’re not just out here adventuring,” said Doran, “we’re out here doing something meaningful.”
The Bookend Trust’s quest to rediscover the short-tailed rain crayfish is captured in the short film Survivors. Doran recently attended the Green Oscars – the 2022 Wildscreen Panda Awards in the UK. Survivors exceeded all expectations, making the top three in its category, alongside productions from the BBC and Netflix.
This sent the good news story of the short-tailed rain crayfish flashing around the world.
Terry Mulhern is a writer and academic. He has lived in Victoria for more than 20 years but, like a swift parrot, he migrates every summer across Bass Strait to north-west Tasmania.
