Conservation of French Polynesian Partula tree snails has been running for over 40 years, since the introduction of the predatory snail Euglandina rosea led to the extinction in the wild of 52 species. Conservation breeding by the Partulid Global Species Management Programme has been successful for 10 species, and some are in substantial numbers. Following the decline of the predator, attempts to re-establish the snails started in 2016 and releases took place every year until the Covid-19 pandemic caused a halt to all reintroductions. In 2023 it became possible to recommence the field conservation programme.
The hiatus between 2020 and 2023 saw several major changes to the programme, with an almost complete break in monitoring because of movement restrictions. At the same time, the programme lost its field biologist to Covid-19. Trevor Coote had been monitoring wild populations and leading the reintroduction efforts since 1995 and his death was a great blow to everyone involved. There were also problems for the ex situ programme as thousands of snails scheduled for release in 2020 had to be accommodated. The lifting of pandemic restrictions meant that reintroductions could once again be planned, taking pressure off the ex situ institutions and reinvigorating the programme. With the loss of Trevor Coote, changes were inevitably required. The French Polynesian Direction de l'Environnement stepped up and have made 2023 a year of exceptionally detailed monitoring. In addition, new collaborations have been established with the ecomuseum Fare Natura.
During 8–15 April 2023, 5,694 snails of seven species were released on Tahiti and Moorea. The Partula conservation programme has always had to be dynamic, requiring constant modification and learning, and this release was our first opportunity to try marking the released snails with UV reflective paint. With UV torches this dramatically improves the detectability of the snails. Previously, once they had dispersed into the canopy, they were effectively impossible to locate, hindering determination of release success or failure. We used a drone to gain access to the canopy, but this was ineffective at detecting small snails in low light; once the most recently released snails have had time to disperse into the canopy, adding a UV light to the drone may solve this problem.
The post-release monitoring has recorded continued presence of many released snails and has confirmed that previous releases have produced at least one self-sustaining population, with the sighting of wild-born adult Partula taeniata on Moorea island. A second release in 2023 will take advantage of the opportunity to establish more species, test out new ideas and give ex situ collections space to focus on the most threatened species. The collaboration between programme participants, and the new approaches to research and releases, is ushering in a new phase in Partula conservation that will also inform wider terrestrial mollusc conservation.
Open access
