New Zealand Island's Ground Beetle Numbers Surge After Invasive Mice Removal

Scientists report that ground beetle numbers on New Zealand's Antipodes Island are about 40 times higher than before invasive mice were eradicated, with rove beetles increasing more than twentyfold following long-term monitoring published in *Conservation Science and Practice*.

A Remote Island Ecosystem Under Pressure

Antipodes Island, a remote subantarctic location in New Zealand, supports seabirds, endemic land birds, and unique invertebrates, including the Antipodes Island snipe and parakeet. For over a century, invasive house mice—introduced via human activity—preyed on surface-dwelling invertebrates such as beetles and spiders, competed with native birds for food, and altered plant dynamics.

The Department of Conservation Te Papa Atawhai undertook the 'Million Dollar Mouse' campaign in 2016, utilizing a 13-strong team and helicopters to distribute cereal bait containing brodifacoum. Monitoring in February 2018 using tracking tunnels and rodent detection dogs confirmed the eradication of mice.

What the New Research Found

Published research examined post-eradication invertebrate recovery, highlighting that ground beetle abundance grew roughly 40-fold while rove beetle numbers rose over twentyfold. These insects play vital roles in processing organic material and supporting local food webs.

• Ecological Indicators: Beetles feature short life cycles, making them effective indicators of ecosystem health.
• Food Chain Impacts: Increased insect populations provide additional food sources for native birds, which earlier surveys noted had also increased following mouse removal.
• Long-term Monitoring: Scientists emphasize that ecological recovery unfolds gradually over multiple breeding cycles rather than occurring overnight.

Practical Implications and Verification

The findings demonstrate the profound, multi-year benefits of pest eradication on vulnerable island ecosystems. Readers can verify the original research by reviewing the published study in *Conservation Science and Practice* or consulting reports from the New Zealand Department of Conservation.