DOC's work with Powelliphanta snails
Powelliphanta hochstetteri obscura
The Department of Conservation undertakes a number of programmes to protect Powelliphanta populations.
Possum control, particularly in the upper South Island, aims to protect several species. On Mt Burnett, in Golden Bay, DOC staff could only find about four live Powelliphanta gilliesi gilliesi snails in every hundred square metres in 1994. By 2003, following two aerial possum control programmes, searchers were finding almost fourteen live snails in every hundred square metres.
On Mt Arthur, in Kahurangi National Park, searchers could only find about three Powelliphanta hochstetteri hochstetteri snails in each of three sampling plots in 1993. By 2003, after a decade of annual ground control of possums, about 15 snails were being found in each plot. At the same time, in a near-by site where no possum control takes place, less than three snails per plot were being found.
Rat control, combined with weed control, revegetation and wetland restoration, is helping to secure a future for the Powelliphanta traversi koputaroa snail near Levin.
Recently, there has been a dramatic drop-off in the number of snail shells being found attacked by rats. In the past, DOC staff found caches of predated snail shells throughout the area, but this is not occurring anymore.
One species, Powelliphanta gilliesi brunnea, is slithering towards recovery in Golden Bay, thanks to a combination of habitat protection and predator control measures. Restricted to half a hectare of farmland, DOC has erected an outer fence to exclude farm stock, an inner fence to exclude rodents and hedgehogs, and has planted native trees to increase the habitat available. By 2003, there were about 1000 individual snails present, compared to about 350-500 in 2001.