It is estimated that the black rats were introduced around 1943. From around this time, all of the large land snails on the island (with shells of more than 10 mm in diameter) declined dramatically and some even became extinct due to rat predation. Currently, the last five large species are all listed as Critically Endangered under the Australian Government’s EPBC Act. Three are assumed extinct on Norfolk Island but may still survive on nearby Phillip Island; one (Mathewsoconcha belli) is extinct in the National Park but survives in a single recreational reserve; and the last, Advena campbelli, was last recorded from empty shells found in the National Park.

In late February this year, the Australian Museum was contacted by Mark Scott, a Norfolk Island local, who had found some large snail shells when conducting surveys for rare plants in the National Park. Luckily, we were in the process of preparing for fieldwork on Norfolk Island, and in early March we met with Mark in the Norfolk Island National Park. We were able to confirm the presence of a small living population of Advena campbelli, confined to a single rainforest gully dotted with tree ferns.

This beautiful but poorly known species is still not out of danger. Many of the empty shells found in the gully were clearly rat-predated, and there were also signs that the area is occupied by feral chickens, another significant predator of snails on Norfolk Island. With rats and chickens still common on the island, a captive breeding program may be the only chance to ensure their survival.

We also located the last known population of Critically Endangered species Mathewsoconcha belli in Hundred Acre Reserve. However, this species appears to have suffered high mortality rates after two years of extremely dry weather on the island, and its numbers are significantly reduced. We were unable to survey Phillip Island due to adverse weather conditions, so the status of the last three Critically Endangered species is still unconfirmed.