Conservationists are asking a familiar-sounding question: Why did the Tasmanian giant freshwater crayfish cross the road?
One answer is, of course, to get to the other side.
The bigger question is why does this unique and endangered species risk becoming roadkill when it could pass through a culvert beneath the road?
The secretary of Mt Roland Landcare, Greg Taylor, says a project funded by Tasmanian Landcare is seeking answers and also hopes to find a solution.
"For a long time, people in Kentish municipality have spotted the giant freshwater crayfish crossing the road but haven't wondered why," Mr Taylor said.
"Perhaps we take it a bit for granted here but I believe it is the only species in Tasmania listed with the IUCN [International Union for Conservation of Nature] as an internationally red-listed threatened species.
"We've been looking into the road crossing issue with the help of some funding and through the volunteer efforts of our group."
First step: sit and wait
The group started by investigating the places where crayfish had been seen crossing the road and established that it was always where culverts channelled creeks under a road.
And where creeks and streams are channelled through a culvert pipe, a deep hole often forms on the downstream side.
The crayfish moving upstream then have to negotiate a slippery step up out of deep water to access the culvert.
Some group members have spent hours on end just watching the downstream side of culvert locations which might prove challenging to a freshwater crayfish.
Against the odds, a volunteer was actually able to witness a crayfish struggling with an attempted climb into the culvert.
"So instead of going through the culvert, they climb the bank and cross the road. Quite slowly and obviously there's a problem with that," Mr Taylor said.
The Mt Roland Landcare group has also engaged the services of the foremost authority on the Tasmanian giant freshwater crayfish, Todd Walsh, to examine the problem and identify solutions to it.
The accidental conservationist
Mr Walsh's education began in his teens when he would catch the crayfish — then colloquially known as lobsters — with his father in the creeks and streams of far north west Tasmania.
"And we'd eat them! Lots of people did, but it's actually more fun to catch, tag and release, to be honest," Mr Walsh said.
"I kind of became an accidental conservationist when the taking of freshwater crayfish was banned in 1998."
Mr Walsh now lives in Brisbane but travels to Tasmania several times a year for freshwater crayfish research and river health assessment work.
"There were gangs of workers, in the old days, when we used to eat them, that would stop by the side of the road and watch them climb the banks. Then, they'd just pick them up," Mr Walsh said.
"And there's stories of people hitch-hiking who'd see them crossing the road so they'd pick them up and put them back in the creek.
"They just won't go through certain culverts. They don't mind the box style so much but the round ones are harder for them.
"They just need something to grip onto so they can climb up in there, otherwise it's the slow walk over the road."
Across his lifetime, Mr Walsh remembers picking up at least a dozen crayfish crossing the road.
He's also rescued them from backyards, swimming pools — even from a herd of cows.
"I've seen them crossing a paddock with 10 or 20 spooked cattle following them around," he said.
Another impressive and somewhat incongruous natural phenomenon Mr Walsh has seen is a freshwater crayfish climbing a cyclone fence.
Next step: ropes and ladders
Inspired by that insight and knowledge of international projects assisting eels and other species, the Mt Roland Landcare volunteers began experimenting with a tool known as mussel rope.
Used in aquaculture, the synthetic rope is made to be knotty, shaggy and irregular, providing potential grip for a climbing crayfish.
"The problem was that it was too light so it would float out of position. But that led onto the next thing, a galvanised chain, interwoven with the rope," Mr Taylor said.
"There's a range of factors to consider here. It has to be amenable to a crayfish but it needs to be durable, environmentally sensitive and then there's the engineering perspective.
"Culverts also perform a purpose, allowing water to get under the road. Obviously, that can't be impeded in any way.
"Another possible solution might be a ladder using fibreglass reinforced plastic (FRP), like you often see now in walkways, lookouts. It's durable, inert and recycled."
Waiting for 'gold'
The process of experimentation is expected to take many months, possibly a couple of years. Another key issue to resolve is how to monitor and verify results.
"What we're looking for is that gold — seeing a crayfish climbing something we've installed in order to get into a culvert," Mr Taylor said.
"Perhaps its remote sensor cameras, maybe even thermal cameras. We might even then find the issue affects other species.
"At one of the sites where crayfish have been observed crossing the road, we have also observed a platypus roadkill.
"There may well be a strong connection between the two."
