Partula tree snails reintroduction
Conservation focus:
Polynesian tree snails
Scientific name:
Partula spp.
IUCN status:
EDGE status:
EW (extinct in the wild)
Not evaluated
Threatened evolutionary history:
Not evaluated
Scientific classification:
Molluscs, Gastropods, Partulidae
Population trend
Under evaluation
Conservation attention
Locally high
Range
Ecological role
The Partula tree snails of French Polynesia are mostly herbivores or generalists, although some species are detritivores or fungivores (breaking down organic substances or eating fungi, respectively). Most species are cross-fertilising hermaphrodites, and all are ovoviviparous (they give birth to live young). The 1-2 mm newborn grow to adulthood in as little as 3-6 months. However, they are long-lived. In captivity Partula taeniata from Moorea has been recorded to live to 17 years. At least on Moorea island, these tiny snails have very small ranges – approximately 200 m2.
Partula snails are significant to the history of genetics, have historically played a role in Polynesian ethnology and are now also an iconic symbol of biodiversity loss. As the “Darwin's finches of the snail world”, they have been studied for more than a century, as their isolated habitat provides perfect conditions for the study of evolution.
Threats
Invasive predators caused the extinction of 56 species within 20 years, and a further 10 species survived only in captivity. Conservation breeding has been successful, and since 2016 a reintroduction programme has been implemented.
Grant
First awarded:
$ 3,600
6 September 2024
Not evaluated
Why support?
Here’s a conservationist’s nightmare: discover (in the middle of the Pacific, of all places!) an array of ancient Partula tree snail species showing adaptive radiation, like Galapagos finches. In 1967, add an alien, invasive African land snail to serve as a human food source, and watch it devour crops instead. To control the pest, add another invasive alien, the carnivorous rosy wolfsnail – and watch it exterminate 56 of those Partula tree snail species and drive most others to become critically endangered or extinct in the wild. Homo sapiens at his best!
Then, a conservationist’s dream: an exception confirming the rule that invertebrates - the backbone of ecosystems - receive very little conservation attention. After over 30 years of a careful Partula breeding programme, over 17,000 snails from 11 Partula species which were extinct in the wild return to their native habitats (including one which had been down to just 9 individuals!). Proof that extinction in the wild can sometimes be reversed, and a truly formidable achievement. We want to be part of it!
Grant focus
Release captive-bred Partula species, monitor survival in the wild
Programme owner
Peterhouse, University of Cambridge, UK
Programme contact
Dr. Justin Gerlach, Director of Studies (Biological Natural Sciences), IUCN Mollusc Specialist Group & Terrestrial Invertebrate Red List Authority
Project location
Tahiti, Moorea
Plage Vaiava, Puna'auia, French Polynesia
Addressing the need: Project goals
To improve monitoring of reintroduced Partula tree snails in French Polynesia by developing a new method for surveying in the forest canopy and to test remote monitoring.
Reintroductions have taken place in most of the past 8 years. We are now starting to find evidence of successful re-establishment in the wild in some species.
The evidence is limited though due to difficulties in surveying the canopy of the forest trees. We plan to test a new method of survey which should allow proper examination of the canopy. On the most developed islands (Tahiti and Moorea) adequate monitoring systems are in place (at least below the canopy). On two other islands (Huahine and Raiatea) access to release sites is more complex and frequent monitoring is not possible.
Monitoring of released Partula and survey of relict populations is an important component of the Partula Action Plan first drafted in 1994 and updated regularly. The need for refinement of monitoring and survey has been apparent for many years as the low-density populations have proven extremely difficult to record with any reliability. Many populations have been thought to have become extinct only to reappear years later, presumably because of movement between visible strata and the canopy. Similarly many released populations have disappeared after a few months without explanation. The Action Plan regards resolving the canopy access as a key improvement for the future.
Conservation actions
The grant provides the equipment necessary to test new monitoring methods. If, as anticipated, these prove effective, they will be used in future monitoring. This will include monthly monitoring of released populations on Tahiti and Moorea. The same methods will also be employed in the 2025 releases.
Critically endangered, captive-bred Partula tree snails are reintroduced to the wild on Tahiti and Moorea. They are shown leaving the transportation bucket.
The fluorescent marks facilitate monitoring of these critically endangered snails after releasing them in the forest canopy on Tahiti
Dr Gerlach and team are testing high level monitoring equipment on Moorea, 16 Sep 2024
Critically endangered, captive-bred Partula tree snails are reintroduced to the wild on Tahiti and Moorea. They are shown leaving the transportation bucket.