Invasive species are a major threat to island ecosystems, where they drive biodiversity loss and extinction. But detecting them can be tough – especially on remote or uninhabited islands where traditional monitoring is expensive and logistically difficult.
The Approach
Building on lab success showing that eDNA testing can detect invasive rodents within an hour, the team at Island Conservation took the approach into the field. In partnership with Wilderlab, University of Auckland and University of Otago, they conducted eDNA monitoring across remote islands in French Polynesia. By sampling water from island coastlines and lakes before and after a rat eradication program, they tested whether aquatic eDNA could reveal the hidden presence of terrestrial pests – and help assess the effectiveness of eradication efforts.
Key Findings
- Prior to the eradication, just two dozen eDNA samples were enough to confirm rat presence with ≥95% confidence.
- A pioneering metabarcoding assay allowed the team to distinguish the presence of two different rat species (Rattus rattus and Rattus exulans) on neighbouring islands.
- After the eradication, neither eDNA monitoring nor camera surveying detected any of the surviving rats, indicating a much sparser population of pest mammals.
What does this mean for pest monitoring?
In island environments, eDNA monitoring offers a rapid, reliable, and cost-effective tool to complement traditional monitoring methods. Especially in remote or difficult-to-access locations, water sampling from island coastlines can detect the presence of invasive land mammals – saving time, effort, and resources.
“The support from Wilderlab over the past couple of years has greatly facilitated our ability to learn and incorporate this tool into our project workflow. We have trained field teams now on multiple island projects in the Pacific and our leading partners and stakeholders are recognizing the potential for the tool. It’s really awesome.”
– Tommy Hall, Island Conservation Palau
We’re excited to continue supporting Island Conservation in their vital work monitoring and eradicating these island invaders.
