Placostylus bivaricosus (a large land snail) - endangered species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Placostylus bivaricosus (Gaskoin, 1855), a large land snail from Lord Howe Island, as an ENDANGERED SPECIES on Part 1 of Schedule 1 of the Threatened Species Conservation Act.

The Scientific Committee has found that:

1. Placostylus bivaricosus is endemic to Lord Howe Island and Rabbit Island (= Blackburn Island) in the lagoon.

2. The subspecies Placostylus bivaricosus bivaricosus (Gascoin, 1885) was formerly common over the northern, lower end of Lord Howe Island from sea level to approximately 200 metres (the top of Malabar Hill). The subspecies P. b. cuniculinsulae (Cox, 1872) occurred formerly on Rabbit Island. The subspecies P. b. etheridgei(Brazier, 1889) occurred in the mountains at the southern end of Lord Howe Island, including the Erskine Valley, to an altitude of 550 metres.

3. The subspecies P. b. bivaricosus now occurs as three disjunct populations, at Windy Point behind dunes, the east end of North Bay at 3-6 metres altitude, and the east end of Neds Beach at 30 metres altitude. The last specimens of P. b. bivaricosus were collected in 1971. The subspecies P. b. cuniculinsulae and P. b. etheridgei are apparently extinct, the latter subspecies not having been collected alive since late last century.

4. The subspecies P. b. bivaricosus lives under litter on the forest floor. It faces threats in all extant populations from rat predation. The subspecies P. b. etheridgei probably declined due to predation from rats and pigs, the subspecies P. b. cuniculinsulae due to predation from feral animals and destruction of habitat.

5. In view of 3 and 4 (above), the Scientific Committee is of the opinion that Placostylus bivaricosus has been reduced in numbers to such a critical level that it is in immediate danger of extinction.

Dr Chris Dickman


Scientific Committee

Gazetted: 4/4/97

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Page last updated: 28 February 2011