Looking for footprints in water
Research on platypus numbers and distribution is being stepped up as science tries new ways to document this elusive Australian species.
IT’S 5AM ON A crisp autumn morning and dawn is more than an hour away as we leave the warmth of our four-wheel-drive to approach the river’s edge.“What do you think?” I excitedly ask platypus expert Josh Griffiths as he peers into the first of two fyke net traps we set the day before. “Hmm, not sure,” he replies. “There’s movement in one net, but it could be a fish, rakali [native water rat] or just the flow of the river.”
Josh is a senior wildlife ecologist withVictoria-based environmental consultancy Cesar. He’s set these traps as part of a Melbourne Water research project exploring the distribution of platypuses in the waterways in and around the Victorian capital.
The project is trying to assess the health of platypus populations and the information it collects helps Melbourne Water assign resources for platypus conservation, through efforts such as environmental flows, revegetation and weed management.
As Josh wades into the water to lift the end of the downstream net, he turns with a grin and asks,“Is your camera turned on?” I don’t need much encouragement to quickly jump into the icy water and take a barrage of shots as he reaches into the net and carefully removes a large male platypus by the tail, avoiding its venomous spurs.After securing him in a cotton bag, we make our way back to our van, where he is gently placed on a pad on the vehicle’s rear tray.
Student volunteer Jessica Pulvirenti brings out a field kit to measure his weight and body and bill lengths, and to take a small skin sample from the webbing on his feet. This will be used back in the lab to analyse the animal’s DNA and familial relationships with other platypuses captured in the area.
This sort of DNA data will also help improve our understanding of local and national genetic diversity. Josh passes a microchip scanner over the male platypus’s neck to see whether he has been caught before.A beep goes off, revealing the presence of a chip that tells us he was first captured as a juvenile about a year ago in this same creek.
Finding this one platypus in this one stream has not been simple.We left Melbourne 17 hours earlier to arrive at about 1pm and, during the next five hours, set up 10 nets at five locations stretching for about 10km of the waterway. Once set up, the nets need three-hourly checking until they’re taken down the following dawn.Then the return trip starts. By the time we arrive home we will have been on the go for 24 hours, with little sleep.
Josh says it’s not always this hard to locate just one platypus. “There are some spots we can pretty much guarantee a capture,” he says explaining that in other places it can take up to four trips.“Then, of course, there are some places where we have never caught anything. That doesn’t necessarily mean they aren’t there, it just means we didn’t catch any – that’s the challenge.”
FEW PEOPLE KNOW as much about platypuses as wildlife ecologist DrTom Grant, who’s studied the semi-aquatic egg-laying mammals for more than four decades and is a member of the University of New SouthWales Platypus Conservation Initiative (PCI) team. Yet even he can’t provide an accurate estimate of numbers.
“[They] are so elusive, so widely distributed but so difficult to study in the wild that, even after all this time, we still don’t have a solid grasp of their abundance or distribution,”Tom says, explaining that he knows of no reliable regional, state or national estimates of numbers. “And that’s a problem.There are documented declines in numbers in some local areas and streams – leading to the prudent downgrading of the species to ‘near threatened’ – and the impact of predicted changes wrought by climate change are of concern. But we just don’t know.
“If we want to ensure that effective management and conservation plans are in place to protect this iconic species, we need to do what we can to understand the threats they face and know how many there are and where they are.”
Tahneal Hawke, also part of the UNSW team, is a studying historical records of platypuses to better understand shifting attitudes to the mammal and its changing distribution. “Looking at newspaper articles can certainly give us some idea of where platypuses used to be in some places,” she says.“However, the accuracy of this approach is limited, because it relies on chance encounters and the sightings being newsworthy.
“For example, a report in the [newspaper] Kerang New Times dated August 1908 noted that 22 platypuses were caught in the Yarra River near Melbourne’s Princess Bridge. However, I’m not sure that any have been seen in that part of the river for a very long time.”
Similarly, during a January 1933 flood, former NSW weekly tabloid The Biz reported that “a shoal of platypus”numbering 15 was seen in Casula.Tom says platypuses are no longer reported in this outer Sydney suburb and are now uncommon in the Georges River that runs through the area.
Researchers are turning increasingly to citizen science for help.
TO BUILD A BETTER picture of platypus numbers and distribution, professional researchers are turning increasingly to citizen science for help and asking members of the public to report platypus sightings.
“Local knowledge is an invaluable source of information and potentially important observations are often made by local residents and outdoor recreationists, which can be overlooked in ecological studies,” Josh explains.
This is where smartphone apps such as platypusSPOT can help. It allows wildlife enthusiasts to contribute to a community-driven database on platypus distribution.
“While some have argued that the quality of data from citizen researchers can be unreliable, photographic evidence of observations entered on platypusSPOT helps minimise this issue,” Josh says, explaining that repeat
sightings by different people create self-verifying data. “Importantly, this application allows data to be collected from a much larger pool of observers, over a wider geographic range and across longer time spans. It just isn’t feasible for research scientists alone to collect data on this scale… for a species as elusive as the platypus.”
Dr Gilad Bino, also with the PCI, is leading an analysis of numbers and distribution across Australia. “We need as much information on their distribution as we can get and it is especially important to find out where they do and don’t live anymore,” he says, agreeing with the widespread call for better platypus population data.
AS WELL AS opportunities now being offered by fledgling citizen science projects, the development of new technologies also promises to make significant contributions to our understanding of platypus numbers and distribution. Among the most exciting new research tools is environmental DNA (eDNA), which allows scientists to observe molecular signatures in water as if they were footprints on land.
“Animals are sloughing off DNA all the time, and even small fragments of DNA allow us to determine whether a particular species is in that sample,” explains Anthony Van Rooyen, a geneticist with Enviro DNA, a commercial offshoot of Cesar. “In terrestrial environments, however, the challenge is that you need to have taken the sample from where the animal has been standing, or at least very close. But the great thing about platypuses is that their DNA gets washed downstream, so you can get an idea whether one has recently been upstream simply by taking a water sample. It’s like CSI but in a river.”
“Our studies show it’s much more sensitive than current netting methods, with about a 95 per cent accuracy of determining the presence of platypuses at a site,” Anthony says. “Of course, it’s much easier, quicker and cheaper than netting.You simply go to a spot in the river, take a water sample, send it to the lab and that’s it. No long nights out with nets, checking every few hours.”
Dr Tiana Preston, a coordinator for Melbourne Water’s water-quality monitoring program Waterwatch, is currently rolling out a plan to use both citizen science and eDNA technology to more effectively monitor vulnerable platypus populations and assist with strategic education and infrastructure decision-making. “The wonderful thing about combining citizen science and this technology is that by engaging residents in collecting the water samples, we empower the community to participate in waterway management, as well as raise awareness of platypuses and the threats they face,” Tiana says, adding that it’s faster than live-trapping, about a tenth of the cost and multiple sites can be covered quickly.
Of course, netting surveys will remain important. They enable identification of individual platypuses, their sex, age and health, and the collection of genetic samples. But for such a large continent and a species such as the platypus with a poorly understood national distribution, eDNA is being seen as an exciting new tool that can better help us understand where the species still occurs.
“My dream,” Josh says, “is that… we can get funding to support the rollout of a national citizen science campaign, where thousands of people from all around Australia can sample their local waterways allowing eDNA technology to give us a better idea of [platypus] distribution.”
It won’t give a definitive answer on where all platypuses may be but will provide a far better idea of distribution than we currently have.
And that, says PCI head Professor Richard Kingsford, could be critical for the species’ future management and conservation. “There is mounting evidence populations are declining due to multiple factors such as habitat destruction, river fragmentation and poor river management,” he warns, “but we just don’t know how many are left or their distribution.
“Anything we can do to get a better handle on platypus distribution and numbers is vital and the use of citizen science, whether it be in the form of spotting and recording them on a smartphone app, or the collection of eDNA samples will be of significant benefit.”