Macquarie Island’s penguins, seals and albatrosses have long been in the scientific limelight but less is known about smaller species that call the sub-Antarctic island home.

More than 350 invertebrates, including spiders, make up the island’s bustling biodiversity.

One of them is an invasive interloper that’s caught the eye of researchers.

Australian Antarctic Division ecologist Dr Justine Shaw said the non-native flatworm Kontikia andersoni first arrived on Macquarie Island from New Zealand with sealers and penguin harvesters more than a century ago.

“While not currently found in Australia, this flatworm is a serious agricultural pest in the UK because the species affects soil processes and eats the good bugs in the soil,” Dr Shaw said.

“The small invasive flatworm preys on other invertebrates and is very tough, able to reproduce itself if chopped in half.”

“It's like a feral cat of the invertebrates in the sense that it's eating all the native things.”

Natural laboratory

A research paper entitled ‘Rapid range expansion of an invasive flatworm, Kontikia andersoni, on sub-Antarctic Macquarie Island’ was recently published in Biological Invasions.

Lead author Dr Melissa Houghton, an entomologist with Biosecurity Tasmania, said understanding how non-native invertebrate species are transported, disperse, establish and colonise new habitats is key to understanding their existing and future impacts.

“We're really interested to understand the impact of invasive or non-native species on native species and ecosystems,” Dr Houghton said.

“Sub-Antarctic islands are natural laboratories that provide great opportunities for this research because there's no agriculture and stable annual climates with no droughts, monsoons or bushfires.”

“This research is fundamental to improving biosecurity practise and informing future management of Southern Ocean islands.”

Finding flatworms

The researchers found the flatworm has expanded its distribution on Macquarie Island over the last 30 years.

But digging up the answers meant getting their hands dirty.

“The way Melissa did her field work was to literally get down in the dirt and look in the leaf litter,” Dr Shaw said.

“She had sticky plates, she was shaking vegetation - all the classic invertebrate monitoring methods.”

“She went round the whole island and surveyed. Every kilometre she'd stop and get down on her hands and knees in the rain.”

The study revealed that the flatworm ‘footprint’ has expanded from a few isolated spots on the east coast, to the west coast of the island.

“Our work demonstrates how quickly these invaders can spread, even on a remote World Heritage island,” Dr Houghton said.

Invading invertebrates

Flatworms thrive along the coast rather than the centre of the 35 kilometre-long island, but this raises a riddle over how they spread.

“We're interested in this jump to the west coast and whether it was with a bird or a human or something else. We probably won't ever be able to know for sure,” Dr Shaw said.

“The flatworms typically live in these lush coastal spots with seal poo, big grasses and wet plants.”

“But the interesting part is we haven’t found them at the research station, which is where all the human activity is.”

The wash up

The AAD works closely with Tasmania Parks and Wildlife Service and Biosecurity Tasmania to ensure biosecurity is at the forefront of operations on World Heritage-listed Macquarie Island.

While southbound biosecurity remains a priority to keep pests off the island, the challenge ahead is to keep the flatworm out of the research station and ultimately, Australia.

The research paper recommends that biosecurity protocols be reviewed to minimise the risk of inadvertently moving invasive flatworms to mainland Tasmania and Australia.

The AAD has reverse biosecurity procedures requiring thorough cleaning of all clothing and equipment used in the field (which includes the areas where the flatworm has been detected) before returning to Tasmania.

“Expeditioners can wash their boots. There's lots of water on Macquarie Island and if you’re walking around the coast, rinsing mud off your boots in the ocean is effective,” Dr Shaw said.

“Of course, that could still be quite daunting to do if it’s minus one but you’re usually already soaking wet.”

Cargo cult

While the flatworm has not been detected at the research station, the risk of introducing these flatworms from Macquarie Island to Tasmania does exist.

Cleaning equipment in field huts aids biosecurity efforts but larger changes could also be on the cards.

“We’re interested in what it means for cargo and cage pallets coming back from Macquarie Island to Australia,” Dr Shaw said.

Cargo moved directly from the field to the ship or station via helicopters during resupply operations could easily transport flatworms.

“If cage pallets go straight from the island to the ship, are they loaded on the deck where there's lots of sea water and natural cleaning? Or do they go straight in the hold with mud that ends up getting loaded on the wharf?”

“This study provides a timely reminder for vigilance to ensure the best possible protection for Macquarie Island and Tasmania, in partnership with the Parks & Wildlife Service, Biosecurity Tasmania, and tourism operators.”

Dr Justine Shaw is leading a new biosecurity project to continue this work under the ARC-funded Securing Antarctic Environmental Futures program, in collaboration with AAD.