Achatinella

These nocturnal snails are found on native trees and large bushes, where they graze fungi from the surfaces of leaves and stems (2). Adults have both male and female parts (they are hermaphrodites) and give birth to live young (2).

All living species of Oahu tree snails are now classified as Critically Endangered due to the devastating decline that their populations have undergone; 17 of the original species have already become extinct (1) (2). Achatinella species are listed as Endangered on the United States Fish and Wildlife Service Endangered Species List (5) and a Recovery Plan has been drawn up in an attempt to secure the future of these critically rare snails (2). The genus is also listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which prohibits trade in this snail (3). The Species Recovery Plan has involved the protection of remaining habitat, and the establishment of captive breeding populations with the aim of introducing individuals back into the wild (2). It is hoped that these broad-based conservation initiatives will help to secure the future of yet another of Hawaii's natural heritage that is teetering on the brink of extinction.

The Oahu tree snails are a classic example of the devastation of the native fauna and flora of the Hawaiian Islands that has occurred following human settlement of the archipelago. Currently, only ten extant species of the genus Achatinella are known (6); these vary greatly in pattern, colour and shape (2), with white and brown shades amongst the commonest colours (6). These small snails have a smooth, glossy shell, which is generally conical in shape (6).

Oahu tree snails are today restricted to mountainous forests above 500 metres (6).

Endemic to the island of Oahu in the Hawaiian archipelago (2).

Members of the genus Achatinella are classified as Critically Endangered (CR) on the IUCN Red List 2007 (1) and listed on Appendix I of CITES (3). A number of species are already classified as Extinct (EX) on the IUCN Red List 2007 (1).

These tree snails were once very abundant on the island of Oahu, so much so that they feature in local folklore and were once popular components of ornaments (2). Since the arrival of humans to the islands of Hawaii however, the native habitat has been relentlessly cleared, persisting only in the more inaccessible reaches of the mountains (2). In addition to the loss of habitat, these snails have also suffered from predation by introduced rats and carnivorous snails such as the large Euglandina rosea (2); this snail was brought to the islands in an attempt to control the numbers of other introduced snail species but which instead decimated local populations (4). The over-collection of shells has further impacted on the population of these rare snails (7).