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MARGINALIA

The Rarest Snail in the World

Do development and scientific study conflict with conservation?

Pat Shipman

Survivors

2011-11MargShipmanFC.jpgClick to Enlarge ImageThe rarest snail in the world is also rare in institutions: Only four museums in the world have specimens. One is the Smithsonian Institution, which sent out an expedition in 1930 that included ornithologist Paul Bartsch, who spent two days collecting snails at Maynard’s original site. In an unpublished article, Bartsch wrote alarmingly that he and his team “found Maynard’s C. nanus quite abundant, and gathered two eight-ounce bottles full of them.” Two bottles full!? We were aghast. After days of fairly diligent searching, we had found about 75 dead snails. Mike had collected a total of 87. Bartsch had clearly taken thousands of snails from Maynard’s original site, which might well have been almost the entire living population in 1930. No wonder Mike found no live snails there in 1975! Had the acquisitiveness of a scientific collector pushed C. nanus into extinction?

This horrifying thought made us stop and reconsider what we were doing. We were picking up shells, like any tourist on the beach, and we hadn’t thought to inquire about a permit. (We did so the very next day.) Were we picking up the last shells ever of C. nanus?

Spurred on by our shared curiosity, Mike dug out and sent us his unpublished field map, which showed where he had found living and dead snails. This guide helped us relocate the old sites. Sadly, we found that a house had been built on Maynard’s original collecting site, where we saw no sign of dwarf Cerion. Next, we searched for the only site where Mike had found living snails in 1975. Following his map, we drove slowly along the road, watching the odometer. Then we crested a slight rise and saw it: an area that had been completely bulldozed and covered in sand for parking heavy construction machinery. Diligent but downhearted searching around its edges yielded only one or two dead C. nanus shells.

Just when we began to fear the worst for C. nanus, we took a hard look at the 2009 Cayman Islands National Biodiversity Plan. We discovered that Mat Cottam, a terrestrial ecologist in the Cayman Islands’ Department of the Environment, had been monitoring the C. nanus population for years, as has Fred Burton, a naturalist based on Grand Cayman. We felt rather foolish: We had been looking for a rare snail that we thought nobody knew about, but Caymanian ecologists had been on the job all along! We contacted Mat right away. At least he had good news. Mat happily told us that he had found live C. nanus in 2010 and expected to find them again in 2011. He also confirmed our hunch that we were hunting C. nanus at the wrong time of year. Mike’s old notes showed that he found live dwarf snails only during the rainy season, but the rains hadn’t yet begun by the time we had to leave the island. Mat verified that in the dry season, C. nanus estivates, going into a state similar to hibernation, and seeks hidden, protected areas. With our holiday snail hunt behind us, we waited for Mat to e-mail us with news that this little mollusk is still alive. We got it in August, with the rainy season in full swing!

What do retired scientists do on vacation? They search for the rarest snail in the world, even though hardly anyone knows it exists and fewer still know it is “missing.” The continued existence of C. nanus will be a quiet sort of triumph. Tiny countries and tiny islands often have big problems with the survival of rare species. Despite the odds, one very small, very uncommon snail—one seemingly insignificant creature of unusual habits and great vulnerability—has survived competition, the paving of roads, bulldozers and development for another year.

Bibliography

  • International Union for the Conservation of Nature. 2001. 2001 IUCN Red List Categories and Criteria version 3.1. Accessed July 2011. http://www.iucnredlist.org/technical-documents/categories-and-criteria.
  • Brunt, M. A., and J. E. Davies, eds. 1994. The Cayman Islands: Natural History and Biogeography. Dordrecht, The Netherlands: Kluwer Academic Publishers.
  • Bartsch, P. 1931. Further explorations for mollusks in the West Indies. In True, W. P., ed. Explorations and Field-Work of the Smithsonian Institution in 1930, pp. 91–102. Washington: Smithsonian Institution.
  • Clench, W. 1964. Land and freshwater Mollusca of the Cayman Islands, West Indies. Occasional Papers on Mollusks 2(31):345–385.
  • Harasewych, M. G., A. J. Baldinger, Y. Villacampa and P. Greenhall. 2007. The Cerion (Mollusca: Gastropoda: Pulmonata: Ceriondae) taxa of Charles Johnson Maynard and their type specimens. Bulletin of the Museum of Comparative Zoology, 158(7):367–523.
  • Hounsome, M. V., and R. R. Askew. 1980. Cerion nanus (Maynard) (Mollusca: Cerionidae) on Little Cayman. Atoll Research Bulletin 241:91–96.
  • Turner, R. D. 1957. Charles Johnson Maynard and his work in malacology. Occasional Papers on Mollusks 2(21):137–152.




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