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The Ua Pou islets Pacific rat eradication operation was undertaken in August-September 2023. It attempted a global first of aerially broadcasting rodent bait by drone from a small ship in open sea across the islets of Motu Tākaè, Motu Oa, and Motu Mokohe, at Ua Pou in the Marquesas Islands. The aerial bait application resulted in only two of the three islands having bait successfully applied across their entirety, nonetheless, monitoring 12 months later has confirmed Motu Oa and Motu Tākaè are rat free as is the partially isolated section of Motu Mokohe that was also baited. The eradication success is supported by the establishment of biosecurity knowledge and practices throughout the Ua Pou communities. The results of the seabird and other environmental monitoring will help sustain a commitment over time, as well as benefiting the wider conservation community. The operation demonstrated that drones could be operated off a boat for rodent eradication purposes but was constrained by the consistently strong winds and swell conditions. A larger vessel with a deeper draught is recommended for similar operations in the future and would likely increase the number of flyable days and improve the ease with which take-offs and landings are undertaken by the drone pilots.

The tropical Marquesas islands are characterised by their isolation and high levels of endemicity among native fauna and flora. This includes forty-two percent of the 320 native vascular plants and a diverse terrestrial snail community, with at least 78 species represented. Of the 12 native land birds 11 occur only within the archipelago, several restricted to a single island. Nineteen species of seabird breed there including the most eastern population of the Endangered Phoenix Petrel. Monitoring of seabirds and other species before, during and after the project will inform the impact of removing rats from these islets including how endangered species respond and community interest.

Breeding success of 5 Cory’s shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several subcolonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Cory’s shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was significantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding success recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year following eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several ecological advantages on more ecosystem components than Cory’s shearwater alone. Improved eradication tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.