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Mongoose eradication achieved on Japanese World Heritage island: social benefits outweigh costs

Published online by Cambridge University Press:  30 July 2025

Takahiro Kubo Open the ORCID record for Takahiro Kubo [Opens in a new window]  and
Kota Mameno Open the ORCID record for Kota Mameno [Opens in a new window]
Takahiro Kubo*
Affiliation:
Biodiversity Division, National Institute for Environmental Studies, Tsukuba, Japan Department of Biology, University of Oxford, Oxford, UK
Kota Mameno
Affiliation:
Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
*
(kubo.takahiro@nies.go.jp)
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Information

Type
Conservation News
Information
Oryx , Volume 59 , Issue 3 , May 2025 , pp. 286
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence CC BY 4.0.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Fauna & Flora International

On 3 September 2024 the Indian mongoose Herpestes auropunctatus, an invasive mammal, was declared successfully eradicated from the Japanese island of Amami Oshima, a 712 km2 UNESCO World Heritage Site, after 31 years of intense effort. Although the island is > 600 times larger than areas where the mongoose has been successfully eradicated elsewhere, and thus it is difficult to confirm absolute eradication, the absence of detections despite continued monitoring resulted in the declaration of eradication.

Intentionally introduced from Bangladesh in 1979 to control pests and a native venomous snake (the Okinawa habu Trimeresurus flavoviridis), the mongoose quickly became an ecological threat, preying on native wildlife such as the Amami rabbit Pentalagus furnessi. The eradication programme was initiated in the 1990s, and from 2005 specialists used a combination of intensive trapping, baiting and advanced monitoring systems, resulting in captured mongoose numbers declining from c. 4,000 in 2000 to < 1,000 in 2007 and < 100 in 2014. In April 2018, one mongoose was caught in a trap, but since then none have been detected with traps, mongoose detection dogs or camera traps.

The programme faced many challenges prior to the declaration of successful eradication. An administrative review conducted in 2012 recommended a drastic reduction of the budget as a result of unclear achievements (i.e. the value of the biodiversity supported by the eradication programme could not be measured) despite the implementation costs. However, a contingent valuation study estimated that the mean willingness to pay for the mongoose-free biodiversity conservation project on Amami Oshima Island was c. 16.93 USD (2,539 JPY) per person. Considering the beneficiaries in Japan, the social benefit of the programme was > 1.69 billion USD (253.9 billion JPY), which significantly exceeded the total programme cost from 2000 to 2024 (c. 23.82 million USD, or 3.57 billion JPY).

Nevertheless, on 7 February 2025, the removal of all mongoose eradication traps on the island was completed. To prevent the reintroduction or new introduction of invasive species, monitoring and management will continue using the knowledge and resources developed through this programme.