South Africa Is Going to Bomb an Island With Tons of Poison. Its Goal: To Annihilate Thousands of Mice

Desperate times call for desperate measures. In ecological terms, the threat of extinction of some species has led experts to inject radioactive material into the horns of rhinoceroses, hunting wild cats, and even eliminating half a million owls. Now, we'll have to add South Africa’s drastic plan to save albatrosses on an island to the list.

The issue on Marion Island. On July 6, 2024, a team of researchers working on Marion Island, a remote sub-Antarctic territory in South Africa, found a severely injured chick, the latest victim in an increasingly rapid series of brutal fatal attacks. The chick was a four-month-old wandering albatross with bleeding wounds on its neck. It died the following day.

These wounds were consistent with injuries inflicted by house mice that were accidentally introduced by seal hunters in the early 19th century. These mice are now threatening the island’s endangered seabirds. Marion Island is home to a quarter of all the world’s wandering albatrosses, making it crucial for the survival of the endangered species.

Mouse-Free Marion Project. That’s the name of the $26 million project that conservationists are developing with government support and a fundraising campaign. Their goal: to kill a million mice on the remote island by bombarding the enclave with tons of poison. In particular, they plan to drop rodenticide-laced pellets all over the island.

It’s a drastic measure, but as we mentioned earlier, it’s not uncommon in the effort to protect species. “[We] predict that the majority of the seabirds on Marion Island, including the wandering albatross, will become locally extinct in the next 30 to 100 years if the mice are not removed,” Anton Wolfaardt, a conservation scientist in Cape Town and the director of the plan, told Canadian radio station CBC.

The island’s history. Marion is a volcanic island in the Indian Ocean, about 1,200 miles southeast of Cape Town. The enclave is designated as a special nature reserve, once a haven for albatrosses, petrels, penguins, and seals. They used to hunt in the sub-Antarctic waves but came ashore to breed and molt. However, everything changed when the mice first arrived on seal-hunting boats some 200 years ago.

The population of rodents has expanded significantly, particularly in recent decades, reaching a peak of a million during certain seasons. Wolfaardt attributes this increase to climate change, as warmer and drier conditions have extended the breeding window for the mice. In fact, researchers have observed that the rodents have adapted to attacking birds by targeting areas where their plumage is thinnest, typically on the head, making it easier for them to access the birds’ soft tissue.

Scalping. Scalping refers to the practice where rodents nibble on birds while they’re still alive. Scientists emphasize that the birds on the island haven’t developed defense strategies against these relatively new predators, and the youngest chicks aren’t yet able to fly.

What’s more, according to Wolfaardt, over time, the birds become fatigued, often dying or succumbing to bacterial infections.

Putting the plan into action. The idea is for a fleet of helicopters to drop poison along precise routes on the island. However, Marion’s size and topographical complexity present unique challenges. Mapping and fine-tuning won’t be ready until at least 2027, given that the team is studying extensive data and making contingency plans around variables such as weather. There’s no margin for error.

In this regard, Wolfaardt told CBC that researchers need to ensure that every part of the island is covered with rodenticide bait to eradicate every single mouse. If they achieve this, the birds will have a temporary respite. However, this will be challenging, considering mice can have four or five litters a year, with six to eight young per litter.

Hydra effect. The plan must be perfect. Science has shown that it could be a disaster otherwise. This is often referred to as the “Hydra effect,” a concept taken from Greek mythology that’s used to describe ecological phenomena where intervening in a system, such as trying to control a pest population, can lead to an unexpected increase in that population or the emergence of new problems.

In this case, when using poison to eradicate a rodent pest, resistant organisms can survive and reproduce, giving rise to a population that’s even more challenging to control and, potentially, stronger and more dangerous.

The case of California crabs. Several years ago, scientists attempted to eliminate the invasive European green crabs from a secluded lagoon in California. For five years, they captured and removed around 90% of the crabs, reducing their population from approximately 100,000 to just under 10,000.

However, the following year, the crab population rebounded to about 300,000. The scientists had overlooked the fact that adult green crabs predate on the young, serving as a natural form of population control, considering a single female can lay up to 185,000 eggs up to twice a year. By eliminating nearly all adult crabs, they inadvertently allowed the next generation to thrive, leading to a significant population increase.

Image | Ifer Endahl (via Unsplash)

Related | Scientists in the 1970s Thought That Larger Animals Should Be More Susceptible to Cancer. They Also Found It Wasn’t the Case