When the eradication of some animals restores an ecosystem
How to preserve and rebalance ecosystems that have been disrupted by man? This sometimes also involves the eradication of animals introduced in certain environments, such as on the French island of Amsterdam in the Indian Ocean.
The survival of some species can be threatened by exotic animals at these latitudes
On this island located 2,800 km from the island of Reunion, there are no inhabitants in the strict sense but a scientific base which welcomes 20 to 40 people depending on the season to study this nature reserve. By 2010, cattle introduced to the island in the late 18th century had been slaughtered. Next year all other animals that have been introduced, voluntarily or not, into this closed environment will also be eradicated. We’re mostly talking about rats and mice here, but also a handful of feral cats – domesticated cats that have returned to the wild. All of them pose a direct or indirect threat to the island’s fauna, especially birds, explains Clément Quetel, deputy director of the French Southern and Antarctic Territories Environment Directorate. “The birds nest on the ground and have not adopted defensive behaviors”explains, adding: “we observe cases of predation by rats that come directly to consume the eggs, or to attack the chicks”. This generates a fairly consistent mortality within the colonies, which over the years can harm the reproduction and survival of the species.
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Among these threatened birds we can mention the rockhopper penguin, the petrel, the yellow-billed albatross (the island is home to two thirds of the world’s population), and finally the Amsterdam albatross, of which only the albatross remains. of 35 couples and nowhere else in the world. But introduced species are also threats to vegetation. ” Phylica arborea was the only shrub present. So mice come to eat the seeds on the trees[celles-ci] do not fall to the ground to germinate” explains Clément Quetel. As for the mice, “They rather attack the young plants, which can endanger the species in certain areas”. It was therefore decided to eliminate these rats, mice and cats. This is an important operation, a project worth over 2 million euros which has been mobilizing a team for years to prepare and verify the results.
Rats are suspected of carrying the bacteria that cause avian cholera
Clément Quetel indicates that the elimination method consists of “spread poison bait” with two helicopters: “These little pellets are made from grains that specifically target rodents, rats and mice. The first objective is obviously to ensure that there are no other species that consume them”. The advantage of the island of Amsterdam is that it welcomes only seabirds, which feed only in the sea, while as far as cats are concerned, they too should be poisoned by consuming these already poisoned rodents. The last felines will then be caught in traps or hunted.
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The eradication of these mammals will also make it possible to verify some scientific hypotheses. Ecoepidemiology Jeremy Tornos, a CNRS researcher, is particularly interested in the methods of propagation of viruses, bacteria and fungi: “in Amsterdam, we know there is avian cholera, which actually affects three species”. It’s a bacterium that we don’t know how it stays in place. “We strongly suspect rats, known to be healthy carriers of this disease” explains the scientist. Finally, once the environment and the natural ecosystem of the island have been restored, it will obviously be necessary to ensure that these animals – exotic at these latitudes – do not return, in particular thanks to the replenishment of the scientific base by boat four times a year. .
Marc Teddy
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