HILO » An agreement between the Nature Conservancy and Ponoholo Ranch on the Big Island will help to protect the island's extremely rare “;singing snail,”; the conservancy announced.

The snail does not really sing, but it has long been known by that name, and there is no question that its existence is threatened by low numbers, despite it not being officially designated an endangered species.

The conservancy and the ranch entered into a 15-year agreement for the nonprofit agency to manage 96 acres of ranch land high in the rain forest of the Kohala Mountains at the north end of the Big Island.

There might be as few as 50 of the snails still surviving, said Sam Gon III, the senior scientist for the conservancy. They are found only in the designated area of Ponoholo Ranch.

Although the federal government has not declared them endangered, the International Union for Conservation of Nature and Natural Resources has them on its Red List of Endangered Species, Gon said.

Before 1992 the snail had not been seen in 46 years, the conservancy said.

The snail must have been much more common in the past, Gon said. It is known in Hawaiian legend by the name pupu kani oe, meaning the shell that makes a sound like a long whistling vibration, he said.

The name probably arose from people hearing forest sounds at night and assuming they came from the snail.

There is no known way the snails could make whistling sounds, Gon said.

The drastic decline in the number of the snails is probably due to loss of ohia forest habitat in the lowlands and predation by rats and non-native “;cannibal snails,”; Gon said.

Ponoholo owner Pono von Holt has already fenced three sides of the 96 acres. The fourth side is a 2,000-foot cliff dropping to the bottom of Honokane Valley.

Most wild cattle have been removed from the degraded native forest, and plans call for removing wild pigs and weeds. The area is also a home for several native birds.