- Manaaki Whenua – Landcare Research Group, Bioeconomy Science Institute, Private Bag 1930, Dunedin 9054, New Zealand
- Department of Conservation, Private Bag 5, Nelson 7042, New Zealand
We describe the effects of aerial 1080 operations on the tracking rates of ship rats, house mice, and mustelids in 13 New Zealand (NZ) regions across public conservation land between 2013 and 2022 using models fitted to 591 573 records of small mammal tracks collected over 24 years. Simulated managed and unmanaged tracking rates show predictable cyclic patterns of response over the six years after aerial 1080 operations, but also strong variation among regions and with environmental variation. Across regions, aerial 1080 operations immediately reduced ship rat tracking rates which remained lower than in unmanaged sites for 1–2 years before rebounding to levels higher than in unmanaged forests for the next 2–3 years. Ship rat rebounds were larger in warmer zones and in northern regions with more diverse low-elevation forests, including red beech and rimu, and smaller in southern and eastern South Island regions with more constrained food resource productivity. Mouse tracking rates were reduced less than those of ship rats and rebounded to levels higher than in unmanaged forests within 6–12 months after aerial 1080 operations in all regions before decreasing to unmanaged rates again. Aerial 1080 operations immediately reduced mustelid tracking rates, which recovered more slowly than rodent tracking rates, especially in cooler and drier South Island regions. Generalised linear mixed effects models showed ship rat irruptions following mast seedfall in 2019 were larger in areas that had received aerial 1080 within the previous four years, and that ship rat abundance increased by the same proportion at all temperatures. Spatial variation in the effects of aerial 1080 operations across NZ has important implications for outcomes for indigenous fauna and hence conservation management. Aerial 1080 operations need to be repeated regularly in sustained programmes to protect NZ’s indigenous forest fauna populations and avoid adverse outcomes for them.