A field expedition on Aldabra Atoll, Seychelles, has resulted in the re-discovery of the Aldabra Banded Snail (Rhachistia aldabrae), which was declared extinct in 2007. This snail was locally abundant in the 1970s but its numbers fell rapidly, likely due to the increasing frequency of dry years on Aldabra as a result of climate change. The last time a living individual of the species was recorded was in 1997.
The snails were found again on 23 August 2014 in dense mixed scrub of a little-visited part of Aldabra by the keen eyes of Junior Skipper Shane Brice of the Seychelles Islands Foundation (SIF). “I was bush-bashing through the scrub when I spotted a mysterious snail that I’d never seen before on the island,” says Shane, “I was very excited!”
“This exciting news shows that you do not need to be a highly qualified scientist to make interesting discoveries,” says Dr Mary Seddon, Chair and Red List Coordinator of the IUCN Species Survival Commission (SSC) Mollusc Specialist Group. “As they are small and well camouflaged, landsnails can survive in small crevices and deep within undergrowth, and hence may be re-found after long periods when they are believed to be extinct.”
On searching the area further, the SIF team located several individuals, including juveniles, which was encouraging as these young snails are considered to be particularly vulnerable to desiccation as a result of reduced rainfall and had not been recorded since 1976.
“I thought deep down, surely it can’t be the endemic snail!” says Catherina Onezia, SIF Senior Ranger and Assistant Training Officer. “I only dared to believe it once I checked it out back at the office”.
The team were exploring infrequently visited parts of Malabar Island, Aldabra’s second largest island, when the snails were found. One of the aims of the field expedition was to document all of the invertebrates observed, but the team never dreamed that they would make such a find. The snails are unmistakeable, with beautiful elongated deep purple shells lined with bright pink bands. Identification of the snails has also been confirmed by mollusc experts Dr Vincent Florens of the University of Mauritius and Seychellois naturalist Pat Matyot.
There is still very little known about the ecology of this rare snail but the re-discovery provides a second chance to protect and study this species in the wild and ensure that it is not lost again. Aldabra is one of the largest raised coral atolls on Earth, with an area of approximately 150 km², most of which lies only 1-2 m above sea level. Climate change impacts such as sea level rise and drought continue to be major threats throughout the snail’s range. Aldabra was designated a World Heritage Site by UNESCO in 1982 and is managed and protected by the Seychelles Islands Foundation.
The atoll is a refuge for many other threatened species including the world’s largest populations of Aldabra Giant Tortoises (Geochelone gigantea) and one of the largest congregations of nesting Green Turtles (Chelonia mydas) in the Indian Ocean.
The re-discovery of the Aldabra Banded Snail provides a beacon of hope. “Despite major global environmental threats like climate change, this discovery shows that investments into protecting unique island biodiversity are well-placed,” says Dr Frauke Fleischer-Dogley, SIF CEO.
For further information, please contact Ms Rowana Walton, Communications Officer at the Seychelles Island Foundation: firstname.lastname@example.org
- Aldabra Banded Snail on The IUCN Red List
- Gerlach, J. (2007). "Short-term climate change and the extinction of the snail Rhachistia aldabrae (Gastropoda: Pulmonata)". Biology Letters 3 (5): 581-584.
- Seychelles Island Foundation