Introduced predator impacts on Norfolk Island’s land snails

Presented by James Joseph Roberts

PhD Candidate, Western Sydney University

Supervisors: Dr Isabel Hyman (AM), A/Prof Kate D. L. Umbers (WSU), Dr Eleanor Drinkwater (WSU)

Island land snails are among the most extinction-prone taxa globally, and Norfolk Island supports some of Australia’s most diverse and threatened snail species. This project integrates ecological, social, and molecular approaches to clarify key threats and guide conservation.

This PhD comprises four chapters. Chapters 1–2 use qualitative data to identify threats and management priorities, incorporating insights from experts and the community. This presentation will focus on Chapters 3–4. Chapter 3 estimates densities of rats and feral chickens across snail habitats using the Random Encounter Model with camera-trap data, identifying when and where management effort would be most effective. Chapter 4 compares the relative predation impact of rats and feral chickens via dietary DNA metabarcoding of faecal samples, enabling detection of soft-bodied prey and helping distinguish predation from scavenging.

Together, these chapters provide an evidence base to prioritise predator management and inform practical strategies to prevent further declines of Norfolk Island’s endemic land snails.