The Lord Howe Placostylus snail is quite large, with a brown, pointed shell up to 7cm long and 2 cm in diameter. The thick shell remains intact for many decades after the animal dies, and the forest floor is littered with many of the dead white shells. The genus Placostylus is a group of large ground dwelling snails with a disjunct distribution in the South west Pacific from the Solomon Islands, Fiji and New Caledonia, to Lord Howe Island and the northern extremity of New Zealand.

From playmate to endangered species

Historical accounts and fossil evidence indicate that the Lord Howe Placostylus was formerly widespread and abundant on the island. The decline was first noted in the 1950’s, and the species is now listed as critically endangered on the 2000 IUCN Red List of Threatened Species. The snails have become so rare that only a few children at the school today have ever seen one alive, whereas in the 1950s school children would find them in the school grounds and play games with them.

The Ship rat Rattus rattus (accidentally introduced in 1918) is considered to be the major predator of the LHI Placostylus and likely to be a significant threat to its survival. European Blackbirds and Song Thrushes (self introduced around 1950) also prey on Placostylus. Another possible contributing factor may include habitat clearing and modification with increased housing in the settlement area.

Recovery actions

To save the snails, the Lord Howe Island Board has initiated a number of objectives, which are now part of the species recovery plan.

The plan details the current knowledge about the snail, documents research and management actions to date and identifies actions required to maximise the opportunity for the species ongoing survival in the wild.

Actions outlined in the plan include additional rat baiting in areas of known Placostylus populations, regeneration of an area of rat free Blackburn Island for possible translocation of Placostylus and control of domestic chickens that forage in forest leaf litter. The Board also investigates options to eradicate rodents from the whole island. As a first step a cost benefit analysis, which was funded by the Foundation, proved that this major effort is financially not only viable but advisable.

Meanwhile, with advice from the New Zealand Department of Conservation, Lord Howe Island Board staff constructed a rodent proof enclosure for the captive breeding and monitoring project.

A safe place to breed and grow

The enclosure has a bird proof roof to keep out, in particular, Blackbirds and Thrushes that may prey upon the juvenile snails. This will secure a breeding population safe from predation from mice, rats and birds, which is critical for the survival of the species as their numbers have declined so much.

Over the next two years, under supervision of LHI Board rangers and local naturalist Ian Hutton, the school children will closely monitor the snails for any eggs laid and then measure growth rates and survival rates of the juvenile snails.

As well as securing a safe breeding population and establishing some basic knowledge of the species, this project will raise community awareness through involvement of school children, an information brochure and progress stories in the local newspaper.

Following the success story of the Woodhen

This is not the fist endangered species breeding program the Foundation for National Parks & Wildlife has been involved with on Lord Howe Island. In 1979 the Foundation provided funding to rescue one of Lord Howe Island’s birds from possible extinction. The Woodhen, a flightless bird unique to the Island, had been reduced by man's activities to just 20 or 30 individual birds surviving on inaccessible mountain summits. The rescue program involved the eradication of introduced pigs and cats and a captive breeding program to increase Woodhen numbers on the Island.

93 Woodhens were raised at the Island breeding centre and released around the Island, and in its day was the most successful captive bird breeding program in the world. Today the Woodhen population is secure, with about 250 to 300 Woodhens living on the Island.

The conservation of threatened invertebrate species is a relatively new issue in NSW. Through awareness of the status of the LHI Placostylus the profile of other invertebrate species will be raised in the community, which will hopefully lead to greater opportunities for the conservation of threatened species and increased protection of biodiversity on Lord Howe Island.