Extinction or survival: partulid tree snails in American Samoa

Four partulid tree snail species are known from American Samoa. In 1998, we surveyed the recently established National Park (units on three islands: T utuila, Tau, Ofu) and neighboring areas for partulids. On Tutuila, Samoana abbreviata, previously considered probably extinct, was extremely rare (15 snails seen); Samoana conica was more common (288 snails) but still rare; E ua zebrina was the most common (1102 snails), at one locality perhaps near its natural abundance. The species have similar distributions within the pa rk. All three have declined dramatically since the 1920s. Before 1980, when the predatory snail Euglandina rosea was introduced, habitat destruction, and perhaps rat predation and shell collecting, probably caused the decline . The Park provides protection to the Tutuila partulids by protecting habit at, although development is still a potential problem. But predation by E. rosea may yet cause their extinction. On Ofu (only outside the Park), 12 li ve Samoana thurstoni were found; 31 have now been recorded by western scien ce. Also, an apparently robust population of E. zebrina. previously conside red a Tutuila endemic, was found. Euglandina rosea is not on Ofu, so these populations are important remnants of the Fauna. No partulids were found on Tau; none has ever been recorded there.