Serving two masters: Reconciling economic and biodiversity outcomes of brushtail possum (Trichosurus vulpecula) fur harvest in an indigenous New Zealand forest

Introduced brushtail possums (Trichosurus vulpecula) cause significant damage to biodiversity values in New Zealand native forests, but their fur and skins also represent an economic resource, particularly to small, predominantly rural Māori (indigenous people of New Zealand) communities. We used harvester interviews, trapping data and a combination of economic and spatial population models to ask whether the seemingly contradictory goals of economically-sustainable harvest and biodiversity protection can both be accommodated in native podocarp-dominated forests in the North Island of New Zealand. Harvesters expected trap-catch indices (TCIs) of 50–70% when initiating a trap-line, stopped trapping when pull-out trap-catch index (POTCI) was 26% (range 20–30%), and left trapped areas for at least 1 year before returning. The effective trapping distance around a trap-line was 200 m and the decline in possum captures on a line over 24 harvest-days declined exponentially from an initial 63% on day 2 to under 8% from day 21 on. timum strategy for sustaining an income of NZ$30,000 from harvest required access to 8–10 lines of 80 traps per year, ceasing trapping at 25% POTCI and leaving possums to recover for 3 years, but this is unlikely to achieve conservation gains. Harvesters could trap to the levels required to achieve these outcomes if subsidized by management agencies that, in return, would benefit from possum control to the same degree, but at lower cost, than current standard ground-control methods.