Anton Wolfaardt has mice on his mind: the South African scientist is leading a project to free Marion Island, 1,900km southeast of Cape Town, of the rodents.
The Mouse-Free Marion Project on the South African-administered island in the Southern Indian Ocean is a partnership between BirdLife South Africa and the South African government to eliminate invasive house mice from the island. If successful, it will be the largest invasive mouse eradication operation in history.
“It just seemed so appropriate that I was being given the chance to give back to the island that started my career,” says Wolfaardt, who first visited Marion Island in 1994. He and his fellow researchers were aware of mice that had inadvertently been introduced by sealers in the 19th century across an area of 31,600ha, and of their impact on the invertebrates and terrestrial ecology of the island. However, at the time the scientists didn’t consider the mice a major threat to the many seabirds that breed there.
Fast-forward 30 years, and warmer, drier conditions have caused the mouse population to balloon.
When Wolfaardt first visited, the mice ate mainly moths and weevils, but food shortages have meant they now forage on whatever they can find — including albatross chicks.
Scientists Stefan and Janine Schoombie were the first people to witness such an attack, in 2015. “The bird was a complete fluffball,” says Janine. “[The mice] just climbed up its back and started nibbling at its head. We could see their teeth going into its flesh.” The bird, too young to walk, let alone fly, could only shake its head in irritation. “As scientists our job is to not intervene,” says Stefan. “But we really wanted to help that bird.”
The plan is to take five or six helicopters to the island in the winter of 2028 to drop poisoned bait pellets. In the meantime, the scientists are fine-tuning their approach to maximise the chances of success, and raising money (helicopter fuel doesn’t come cheap). “Success is not assured,” says Wolfaardt. “But if we achieve it — and we believe we can — the outcomes will be immense. Conservation rarely has silver bullets, but eradicating introduced species from islands is the closest we have to one.”
In late 1993, the final year of his BSc course in zoology and environmental and geographical science at the University of Cape Town, Wolfaardt noticed a faded sign on the faculty noticeboard. “Field Assistants: Seabirds (x2 posts),” it read. “Marion Island, 14-month contract.”
He’d been planning to go straight into the honours programme. But after speaking to seabird biologist John Cooper — who’d visited the island almost every year since 1978 — Wolfaardt applied.
“The year I spent studying seabirds on that wild and wonderful island changed the course of my life,” he says. “I came back from Marion completely enthused by seabirds and islands.”
His next gig was on Dassen Island off the west coast, near Yzerfontein, where he and his artist wife, Leigh, spent five years studying and protecting penguins. In June 2000 a bulk ore carrier, MV Treasure, sank midway between Dassen and Robben islands, both homes to big penguin colonies. The ship spilt about 1,300t of bunker oil, oiling thousands of birds and placing many more in peril.
In addition to participating in a huge de-oiling operation, Wolfaardt also co-ordinated the evacuation from the two islands of about 19,000 clean penguins, which were transported by sheep truck to Gqeberha. “The idea was that by the time they had swum back to their homes [the islands] would be cleared of oil,” he says. “And it worked.”
Once the spill had been dealt with, Wolfaardt mined his first-hand experience for a PhD that looked at the impact of oil spills on African penguins and the conservation benefits of de-oiling. “Until then most of the evidence had been anecdotal and scattered,” says Wolfaardt. He and his colleagues were able to show there was value in rehabilitating oiled African penguins. “And that South Africa, and Sanccob [the Southern African Foundation for the Conservation of Coastal Birds] in particular, were world leaders.”
In 2008, Wolfaardt got to work in the Falkland Islands for the UK government. His job was to co-ordinate the UK South Atlantic Overseas Territories’ involvement in the Agreement on the Conservation of Albatrosses and Petrels.
“These birds pay no attention to national boundaries,” he says. “So it is imperative that countries work together.” He spent five years living and working (and surfing) in the Falklands, but also doing fieldwork on Tristan da Cunha and South Georgia. A major part of his job was trying to mitigate “fisheries bycatch” — every year thousands of albatrosses and other seabirds are killed after eating longline fishing baits and getting snared in trawl gear.
By the time Mouse-Free Marion came calling in 2021, Wolfaardt had built up an impressive CV. But he was aware that this next gig would be career defining. “Whatever happens, it’s going to be the most important thing I ever do in conservation,” he says.
Marion Island and neighbouring Prince Edward Island (which doesn’t have any mice) are the breeding ground for 50% of the world’s wandering albatrosses. All told, 19 of the 29 bird species that nest on Marion face local eradication because of the mice. Of these, Marion is considered globally important for wandering, grey-headed, sooty and light-mantled albatrosses.
The decision to eradicate the mice was not taken lightly, says Wolfaardt. “I’m a biologist. I don’t like killing things.”
Eradication was first discussed seriously more than a decade ago. A 2015 study found that eliminating the mice was technically possible, while an ethics assessment conducted in 2022 showed that doing nothing and leaving the mice to destroy the island’s ecosystem was not an ethically neutral action. “It’s a necessary step,” Wolfaardt emphasises, “to right the human-inflicted wrongs of the past.”
As the project manager, Wolfaardt has focused on assembling a team of the world’s best. A case in point is Keith Springer, a no-nonsense New Zealander who prides himself on not being a scientist.
New Zealand has no native land mammals (unless bats count), but rats, mice, stoats and cats that were introduced have wreaked havoc on local species. In 1960s the government began clearing tiny islands of pests to give native birds safe havens to breed. Over the years, it embarked on more ambitious projects, clearing more than 300 islands of pests.
Springer oversaw many of these operations. He worked on the largest eradication of mice to date (on Macquarie Island) and of rats (on South Georgia, which is about 12 times bigger than Marion), among other projects. The FM caught up with him while he was sailing back from Marion Island. “We did a seven-day test in a 9ha section of the island,” he says. “We tried different-sized pellets to see how long they remained effective in Marion’s ever-changing weather conditions and we kept a close eye on mouse activity over the seven days.” They also looked at trapped mice under UV light to confirm that the rodents had consumed the bait.
Visiting the island gave Springer insights into how to approach the final eradication. But it also underlined the overall importance of the project. “Every morning there were albatross chicks that had been attacked by mice overnight. It was just so heartbreaking to watch these magnificent birds slowly die before they had even taken flight.” That’s why he is hellbent on leaving nothing to chance for 2028 to ensure the team does its utmost to eradicate mice from the island.
Springer knows from experience that it’s all about controlling the things he can — people, equipment, plans — and hoping for decent weather. “Bad weather could make life tricky for the helicopter pilots,” he says. “But when you’re working on something as complex as this you’re nominating your timeline years in advance. You can’t change plans at the last minute.”
He feels the pressure. “You have to miss only two mice out of however many million and you’re back where you started.” But he is also bullish. “That’s why we’re putting in the time and effort and money to make sure we get them all.”
Wolfaardt and Springer know if they don’t succeed it will be decades before they can try again. They also know that, besides recent high-profile failures on Gough Island (in the South Atlantic) and Midway Atoll (near Hawaii), most eradication projects over the past 15 years have been successful.
And few, if any, of these projects have been as carefully planned as the Marion one.
Wolfaardt says it’s the prospect of success — rather than the fear of failure — that drives him. “I’ve worked in conservation all my life,” he says. “And this is the only situation I’ve encountered where we can actually turn back the clock. We are confident we can succeed. And if we do, we can say with absolute certainty that the conservation gains will be huge — and they will endure and grow for generations to come.”
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