Under the steep rolling hills of eastern Victoria are “gurgling” creatures farmers can hear but rarely lay eyes on.
“It’s kind of a strange little thing, that we’re passionate about something we never see,” farm manager Burke Brandon said.
“But still, we know they’re there.
“They’re kind of like our hidden allies.”
The south Gippsland organic beef and lamb farmer is talking about a species of annelid worm called the giant Gippsland earthworm (Megascolides australis).
It earns the name “giant” because an average adult is a metre long — making it one of the biggest earthworms in the world.
An adult giant Gippsland earthworm is on average a metre long. (Supplied: Beverley Van Praagh)
Mr Brandon had heard people talk about them but it was not until a mudslide about 10 years ago that he found them on his property.
“I actually saw a part of a giant earthworm, which was quite a surprise when you actually see how big they are in real life,” he said.
“And we have seen cases where there’s been accidental erosion or a landslip … and you can see in the soil profile these hundreds of little holes in the soil the size of your finger.”
Part of a giant earthworm Burke Brandon found on his property more than 10 years ago. (Supplied: Burke Brandon)
Stomp around and listen
The farmer is getting to know where these elusive creatures live on his property at Moyarra, 125 kilometres south-east of Melbourne, as they don’t travel far.
“You know they’ll always be roughly in the same area,” Mr Brandon said.
Stomping the ground is known as a good way to tell if giant earthworms are around – the ground can gurgle in response. (ABC News: Anne Simmons)
“The more we stomp around on the surface, the more you hear them moving,” Mr Brandon said.
“They feel the vibrations of you walking around, that’s when they scurry back into their holes.
“It makes a gurgling sound, like you’ve let the water out of the bathtub.”
Mr Brandon now wants to understand more about protecting the species listed as endangered in Victoria.
He is one of several farmers taking part in a project mapping the sites of local colonies.
Not too wet, not too dry
The species is endemic to west and south Gippsland and is fussy about its underground home.
Dr Beverley Van Praagh has been studying the worms for more than 30 years and describes them as the “Goldilocks of the earthworm world”.
“They don’t like it too wet, they don’t like it too dry. It has to be just right for them to be able to survive in those clay soils,” Dr Van Praagh said.
A burrow of a giant Gippsland earthworm. (Supplied: Beverley Van Praagh)
The biggest threats to the species are changes in soil conditions, which could come from new housing estates, damming a creek or redirecting a waterway, she said.
Another less obvious threat could be planting trees on top of them with the best intentions.
“When people plant dense vegetation on top of earthworm habitat, it sucks the water out of the soil,” she said.
The worms prefer specific soil conditions and are often found in the banks of small creeks. (Supplied: Beverley Van Praagh)
An idyllic rural home
Most giant Gippsland earthworms are found on private farming land.
A telltale clue the species is lurking under the soil is terracing across hill sides.
Dr Van Praagh said the worms are often found along the banks of small creeks or tributaries or on south or west-facing hill slopes.
Terraces on Mr Brandon’s property — a sign earthworms could live beneath. (ABC News: Anne Simmons)
But when it comes to the exact soil conditions they like, there are knowledge gaps.
Gippsland Threatened Species Action Group and the Bass Coast and South Gippsland Landcare Networks are leading a new project to better understand these parameters.
It has federal funding under the Saving Native Species Program and will involve mapping colonies on private land and studying the hydrology with probes.
South Gippsland, where the species lives, is known for its picturesque rolling pastures. (ABC News: Anne Simmons)
Co-existing with worms
The project aims to help farmers understand how to coexist with giant earthworms and still have productive farmland.
Researchers will track soil hydrology over time, looking at changes in moisture, temperature and oxygen.
Mr Brandon hopes to help preserve the species on his property for years.
“Some areas we may fence off so we know we can manage that area differently with grazing,” he said.
“There is the potential for those areas to be revegetated with plants that coexist well with the earthworms, so grasses and ferns and sedges and small shrubs, but certainly not eucalyptus trees or deep-rooted trees.
“It’s about being aware of how we can incorporate those [earthworm] communities in our whole farm plan, into our long-term future.”
