Conservation Success
Amami-Oshima just became the largest island in the world to completely remove an invasive predator. How did our Japanese colleagues do it? And what does that mean for the rest of the world? Global Center for Species Survival Invertebrate Conservation Coordinator Dr. Sérgio Henriques traveled to Japan recently and provided the following field notes.
The Mongoose & The Rabbit
In August and September 2024, I was in Japan to attend the 27th International Congress of Entomology (ICE2024), and to travel to Amami-Oshima Island. During my visit, the Japanese Ministry of the Environment shared some remarkable news; they declared the eradication (meaning the removal of all individuals) of an invasive alien species from Amami-Oshima. Mongooses were first brought to the island in 1979 to control the native habu vipers, but like many such introductions (such as introducing cane toads to Australia to control sugarcane beetles), this approach proved to be a very bad idea. The mongooses attacked the Endangered Amami rabbit – a species only found in Japan and a natural treasure of the country.
At its peak, it was estimated that the mongoose population in Amami-Oshima reached 10,000 individuals. Then in 1993, a mongoose control project was tested and fully implemented within seven years. After setting 30,000 traps, installing sensor cameras across the whole island, and most importantly involving local residents known as the “Amami Mongoose Busters,” the mongoose population began to drop. It took nearly 20 years to capture 32,600 mongooses, but September 2024 marks six years without a single mongoose capture. Therefore, Japanese conservationists are confident that mongooses have been successfully eradicated from the whole island. This marks the first time an established invasive predator has been eradicated from such a large island, which was considered impossible to achieve. This is particularly remarkable when we consider that all other successful predator eradication campaigns on islands larger than 2,500 ha (except Santa Catalina with 3,020 hectares), have used primarily poisoning. This was not the case in Amami-Oshima, which is over 71,200 hectares.
It is truly a conservation win, and the whole world is watching and learning from Japan’s success. Within days of the news, the IUCN Species Survival Commission’s (SSC) Global Invasive Species Database was updated. Dr. Piero Genovesi (chair of the IUCN SSC Invasive Species Specialist Group) said that the “eradication of mongooses from Amami-Oshima Island in Japan is a groundbreaking initiative that demonstrates how, with sufficient willpower, we can truly make progress in our efforts to conserve biodiversity.”
It’s hard to put into words the sense of elation I felt from my Japanese colleagues that day, and from that Island’s community at large. It was clearly a moment of humble pride for them – from school children to restaurant owners, everyone seemed happy to politely share the good news with their visiting “Spider-Man.”
The Ant and The Spider
As co-chair of the IUCN SSC Spider and Scorpion Specialist Group, I am sometimes called “Spider-Man.” I was on Amami-Oshima Island to work with our Japanese colleagues to study and protect Amami’s kimuragumo, a remarkable group of trapdoor spiders that are Evolutionary Distinct and Globally Endangered (EDGE). Three endemic species are only found on Amami-Oshima. Similarly to the Amami rabbit threatened by the invasive mongoose, Amami’s kimuragumo are likely threatened by the invasive big-headed ant.
As my colleague Dr. Mariko Suziki told me about her work in Amami-Oshima, “The Amami Rabbit still faces threats on the island, such as roadkill or the impact of feral cats, and we continue working to tackle these challenges, but we must also work to protect all biodiversity, from the smallest to the largest species, so we can all thrive”. The question in both our minds was – how do we apply the success of the mongoose eradication to other invasive species on the island?
The process that eradicated the mongoose could work for the ants: test control methods; long term implementation of the approach that works best; systematically and strategically set devices to remove the invasive ants from the environment; implement a monitoring program (much like the sensor cameras for mongoose); and importantly, recruit the active involvement of local residents, perhaps encouraging the formation of an “Amami Ant Busters” team. We are looking forward to the next steps and will be sure to share more stories of conservation optimism from our colleagues in Japan and elsewhere in the world.
This blog was a collaboration between experts at the Global Center for Species Survival, including Invertebrate Conservation Coordinator Dr. Sérgio Henriques.
Published October 26, 2024