A scientist shows a rat, an introduced animal causing great harm, on December 29, 2022 on the island of Amsterdam, which is part of France’s Southern and Antarctic Lands (TAAF) ( AFP / PATRICK HERTZOG )
The island of Amsterdam, part of France’s Southern and Antarctic Territories (TAAF) along with Crozet and Kerguelen, will undergo an operation in 2024 to eradicate introduced animals, cats and rodents, whose presence is causing great damage to the ecosystem. .
After centuries of voluntary or involuntary human introduction of mammals and exotic plants to the southern lands, the conservation area created in 2006 must restore balance to these very fragile sub-Antarctic islands. Even if it means difficult measures to eradicate or limit invasive species such as rodents, rats and mice, wild cats – domestic cats returned to the wild – reindeer or rabbits.
In Amsterdam, “the Reci project (restoration of island ecosystems in the Indian Ocean) aims to eradicate rats, cats and mice by winter 2024,” explains Lorien Boujot, engineer for the management of introduced mammals in Amsterdam, to the environment ministry TAAF.
“Cats and rats have been the main cause of the disappearance of a dozen species of nesting birds since they were introduced to Amsterdam,” he says. Rats tend to prey on eggs or even chicks + and cats can attack adult animals.
Map of the Southern Hemisphere showing French Southern and Antarctic Territories (AFP/)
In addition, “Rats are carriers and vectors of avian cholera disease. It’s likely that this disease was introduced to the island when there was a chicken coop, and now year after year it decimates the reproduction of the existing yellow-billed albatrosses on the “Entrecasteaux” cliffs in the south of the island, adds Lorien Boujot.
Mice have a major impact on vegetation.
“They eat a lot of inflorescences and seeds of native plants like phylica, a shrub that formed a belt around the whole island and for which there is almost no natural regeneration.” Agents try to transplant young phylica, but “rats tend to eat young plants to eat and break,” emphasizes Lorien Boujot.
– Eradication at 2 million –
Planned for the southern winter of 2024, the eradication campaign will consist of two aerial spraying campaigns over the entire 55 km² island, which is very rugged, three weeks apart. “The difficulty is that if we miss a rodent’s vital area, the operation will fail,” says Lorien Boujot.
“Preliminary studies have been carried out since 2017 to better understand the target species. Above all, it is important not to interfere with the full reproduction, because there is a risk of leaving young animals in the hole, unaffected by the eradication methods,” insists – he.
The Reci project is also providing on-site teams to perhaps capture and shoot the last remaining cats present, Mr Boujot specifies.
Armed with a hunting license, Louis Gillardin and Brieuc Leballeur, two field agents specializing in “introduced mammals”, take on this difficult task for the 2023 wintering season.
“Last year our predecessors exterminated seven + individuals + and it’s been a month and a half, two months since we haven’t seen any more on the forty camera traps. We think there could possibly be one to five left,” says Louis Gilardin. And to add: “I’ve never killed a cat in my life and if that happens it won’t make me happy… If she disappeared, it would suit us!”.
A sunrise over the island of Amsterdam, which is part of France’s Southern and Antarctic Territories (TAAF), on December 29, 2022 ( AFP / PATRICK HERTZOG )
According to Brieuc Leballeur, ornithologists are finding that chick mortality has been reduced since he set rat traps around the yellow-nosed albatross colony. “The preservation of ecosystems” is the point of all this work, he states.
At the end of the 2024 eradication campaign, one has to wait two years without being discovered that the operation is successful and “after ten years” the return of the bird species that have stopped nesting Amsterdam, says Lorien Boujot.
Jérémy Tornos, a CNRS ecoepidemiology researcher, is excited for this operation to be completed for the benefit of the birds. And especially for the Yellow-billed Albatross colony, where “a decline in chick survival rates has been observed since the 1980s.”
After eradication, “we will be able to see the impact of the rat, the predator, and the pathogen source. We don’t know if rats are carriers of avian cholera and transmit it to the birds that bite it, or if they are carriers because they eat carrier birds the researcher.
But this model cannot be replicated on all islands, despite the devastation that rodents and wild cats wreak on Kerguelen, not to mention rabbits and reindeer.
“These are very serious measures. The eradication in Amsterdam is a budget of more than two million euros that mobilizes a team over years. We cannot do them all at the same time,” assures Clément Quetel, deputy director of the TAAF environmental department.
In Kerguelen, “It is simply impossible, from a material, financial, human and logistical point of view, to predict the eradication of the mouse, which is present almost everywhere, he says eradicate, we limit” with targeted “trap and shoot” actions.
– “Biosecurity” –
It is then necessary to ensure that rats and mice do not return, thanks in particular to human activities, and therefore apply a “biosecurity” policy. Kevin Nory is therefore responsible for ensuring that the ship Marion Dufresne, which supplies the bases four times a year, does not become a means of transport from its home port in Réunion or from one island to another.
He works at the level of the suppliers, the carrier, on the quay before then boarding in the districts.
Kevin Nory sinks into the bowels of the ship and also regularly checks whether the rat poison in about thirty boxes has been eaten. He takes care of the removal of household waste from the bases, which has to arrive on the boat in airtight containers.
“Rather a good sign” that he has not found any trace of rodents on the boat since mid-2021.