Desperate situations once again lead to extreme measures. Saving one species sometimes means “exterminating” another. We have seen this in South Africa, with the plan to eradicate rats, or the plan to inject radioactive material into rhino horns, the poaching of wild cats, or the plan to destroy half a million owls. But sometimes things don’t go the way governments think. Japan knows this all too well.

The ’79 incident. The story begins in 1979 on the Japanese island of Amami Ōshima, located in Kagoshima Prefecture. That same year, they rediscovered the Amami rabbit (Pentalagus furnessi), an endemic species considered a “living fossil” due to its evolutionary history. Before the discovery, the rabbit was thought to be in danger of extinction due to habitat loss and hunting.

The discovery was a before and after for the species’ conservation, highlighting the importance of preserving the island’s habitat, which is home to many unique species. It also highlighted the need for greater conservation efforts, such as eradicating or controlling the snake population on Amami Ōshima.

A false “bomb”. So a few months later, Japan launched a plan. It brought about 30 mongooses to the island in order to eliminate the snake population, especially the habu (Trimeresurus flavoviridis), which posed a threat to the local population. On paper, the idea was a foolproof plan: The mongooses, the snakes’ natural predators, would reduce the number of habu and increase security on the island at all levels.

But this project was far from infallible. The mongoose was not the ideal creature for snake extermination. First, since they were active during the day, they were unable to catch the nocturnal habu snakes that continued to live without problems in the following years. As a result, the ecological impact was huge.

A specimen of Trimeresurus flavoviridis

Hunting of endemic species. So, during the day, instead of focusing on habu snakes, the mongooses began to prey on a wide range of native species, including those that had no natural enemies on the island until then. This had a serious impact on the local fauna, especially endemic and endangered species such as the Amami rabbit, which had been happily announced months earlier.

Hundreds of thousands of mongooses. The situation had reached the point where mongooses, introduced to eradicate one pest, had mutated into an even larger and more dangerous pest, reaching a peak of around 10,000 species around 2000. In fact, Japan had already started an epidemic in 1993, with a mongoose control project that was expanded over time.

Like? About 30,000 traps have been set up on the island to catch the animals, and cameras with sensors have been installed to monitor them. In addition, locals have formed a team called Amami Mongoose Busters, which specializes in catching mongooses (they have caught thousands of them).

Last? The last official mongoose was caught on the island in 2018. In the incident that occurred in April, the expert panel tasked with determining whether the animal was eradicated from the island, since no living creature had been caught for a long time, estimated the eradication rate to be between 98.8 and 98.8. A preliminary conclusion was reached last February, with a rate of 99.8%, indicating that it is reasonable to say/think that mongooses have been eradicated from the island under current conditions.

Finally, on September 3, Japan’s Ministry of Environment announced the eradication of non-native mongooses from Amami-Oshima Island, a UNESCO World Heritage Site. The statement was based on the expert group’s scientifically based opinion, considering that the mongooses had not been caught for more than six years since their last capture in April 2018.

A unique situation. The ministry did not hide the disaster that took place in 1979, when it tried to control the snakes. In fact, as the administration explained, this is one of the largest cases in the world where non-native mongooses have been eradicated in a very long time.

Following the announcement, the ministry announced that it would remove the traps set on the island, but would continue to monitor it with cameras to prevent a new group of these little creatures from entering the island again. After all, if it took half a century to remove them, any emergency method is more than understandable.

Image | Animalia, TANAKA Juuyoh, Patrick Randall

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