The Impact of Mongooses on the Ecosystem in Japan's Amami Oshima - Status in the 2020s (October 2020)

The Impact of Mongooses on the Ecosystem in Japan's Amami Oshima - Status in the 2020s (October 2020)

In the 2020s, the invasive mongoose species, which was introduced to Amami Oshima and Okinawa Prefecture, continues to severely impact the ecosystem. In particular, in Amami Oshima, endemic species such as the Amami rabbit and the Lidth's jay have continued to be preyed upon, causing their habitats to shrink significantly. A 2021 survey estimated that the population of the Amami rabbit had fallen to around 5,000, highlighting the increasing threat of extinction.

Efforts to eradicate the mongoose continue, but the capture rate has been declining. Since the late 2010s, only about 3,000 mongooses are being captured annually. This is because the mongoose population has spread throughout Amami Oshima, making it more difficult to capture them. In 2022, the Ministry of the Environment and local governments in Amami Oshima introduced new eradication programs, including the use of capture traps and automated tracking systems. However, these efforts cost approximately 100 million yen annually.

Furthermore, the forests of Amami Oshima are among the most biodiverse in Japan and are internationally recognized as important conservation areas. In 2019, the area was designated as a UNESCO World Natural Heritage Site under the name "Amami and Ryukyu." However, despite this recognition, the range of the mongoose continues to expand, and the challenges to environmental conservation remain unresolved. Notably, rare species like the Amami woodcock and the Ryukyu long-haired rat have become new prey targets, putting the entire island's ecosystem in jeopardy.

On the corporate side, Fujitec, which develops animal control devices, and Inopit, a startup that uses AI technology for wildlife monitoring, have collaborated to conduct trials in 2021, installing AI-driven capture traps. While these efforts aim to improve the efficiency of capturing mongooses, their effectiveness remains limited.

To eradicate mongooses, warfarin-based rodenticides are used, mixed into bait. However, the use of warfarin raises concerns about its impact on the entire ecosystem, especially the risk of accidental ingestion by native species. Therefore, physical eradication through capture traps is recommended, but this method has its limits in terms of labor and cost.

Currently, fully eradicating mongooses across Amami Oshima remains a difficult task. The goal is to reduce the mongoose population by more than 90% by 2030, but achieving this will require even more large-scale measures.