Did you hear the one about the whale DNA found in the mountains?
A weird thing happened in the world of environmental DNA.
eDNA, as it’s known, is used by biologists and conservationists to determine what living things are shedding DNA into an environment.
eDNA is most often collected from water in rivers, lakes and seashores. The process is something like how Covid is detected in wastewater. But instead of looking for one virus, the lab technician compares all of the eDNA collected with large databases of known and unique DNA samples.
In New Zealand, eDNA sampling regularly turns up dogs, rats, trout, shags, podocarp trees and so forth. But also macroinvertebrates, reptiles, amphibians, fungi and bacteria.
So when a water sample collected by Zero Invasive Predators came back with DNA from a gray’s beaked whale there was consternation. That’s because the sample was collected about 20km east of Franz Josef village and many hundreds of metres above sea level. A whale is “you know, not a mountain creature”, said Dr Nick Foster, a predator ecologist at Zip.
He asked the lab to double-check their procedures and contamination was ruled out. “As far as we can tell, the ... whale may have died and washed up on a beach and a seagull may have ... scavenged some of it and flew to the alpine zone and did a few poops. Or something like that,” Foster said.
There was also seagull DNA in that sample, observed Shaun Wilkinson, founder and managing director of Wellington-based eDNA company Wilderlabs, which processed the whale sample.
“It’s a fact of life: DNA gets transferred around by birds,” he said.
And animals do unexpected things. DNA from a native long-tailed bat (pekapeka-tou-roa) was found in water samples collected by the Styx Living Laboratory Trust in north Christchurch in 2022.
This native bat hadn’t been seen in Christchurch since 1885 and the closest populations are thought to be near Geraldine, according to DOC.
The trust was thrilled and wanted to confirm the result. It used more conventional tools for detecting bats and continued to collect water samples for eDNA analysis. But no bats were discovered. So another mystery.
Most eDNA work is more positive.
In late 2021, DOC rangers sampled water in the upper Clutha Valley and detected an unknown population of Clutha flathead galaxias, an endangered native fish. Steps have been taken to prevent trout eating them. “Given the threats these fish face, it’s amazing to discover a new population. Now it’s on us to ensure it survives,” a DOC ranger told The Press in April.
Otago University geneticist Dr Neil Gemmell has a student trialling eDNA detection for Bennett’s wallabies in South Canterbury. The marsupial pests are supposed to be contained between the Rangitata and Waitaki rivers, but have burst those borders and will probably be in Ashburton, Wānaka and Dunedin by 2065 if nothing is done.
The first step is looking for wallaby eDNA fingerprints in places where they are known to be – because they’re wearing radio collars. If that proves successful, they can start seeking them further afield.
“We don’t have a good handle on how far they’re dispersed and where they are,” said Gemmell.
Wallabies are most active at dawn and dusk, they’re naturally elusive and can move fast and far. It’s hoped eDNA will play a role in the eventual eradication of wallabies in Aotearoa.
Meanwhile, eDNA played a role in the discovery of gold clams in the Waikato River this year. Under favourable conditions, the clams can produce 400 juveniles a day and 70,000 juveniles a year. They crowd out native species and block water channels, irrigation pipes, stormwater infrastructure, water treatment facilities and power stations.
After the discovery by fresh water researchers, Wilkinson’s company went looking for gold clam DNA in water it had analysed recently and others that were kept frozen for exactly this sort of situation.
Sure enough, gold clam DNA turned up in a sample taken about a month before the discovery and dating back to September 2022.
There was no reason to be looking for gold clams until that point, Wilkinson said. The company deals with about 10,000 DNA detections a day and can’t spot every anomaly.
Wilderlabs have now integrated a new clam assay into its comprehensive tests that includes gold clams, zebra mussel and quagga mussel. And, since July, more than 2500 eDNA samples from across the country have been screened using the clam assay and no gold clams have been found outside the Waikato.
“It’s a fact of life: DNA gets transferred around by birds.”
Shaun Wilkinson