The leghold trap is by far our most effective tool for invading possums, intercepting approximately 60% of those that attempt to pass through each defence line.
When ZIP began operations at Bottle Rock in late 2014, our leghold traps were lured using a 90x90mm white corflute chew card baited with aniseed possum lure, refreshed every 6 weeks.
However, when we observed catch data over time, it became clear that refreshing the lures did little to improve trap effectiveness, and catch rates did not reduce between services.
We now believe that the visual ‘flag’ created by the white corflute square is acting as the attractant, and is itself sufficient to cause possums to investigate traps.
Following the ‘lonely’ rat releases on Bottle Rock between July and September 2015, we began to reconsider our approach to detecting invaders in the Remove and Protect system.
These releases demonstrated to us that the ‘footprint’ of an individual Ship rat in the landscape can be very small and therefore extremely difficult to detect using current methods.
We are now looking to determine whether the dispersal footprint of a first generation breeding event is both detectable and manageable using currently available tools.
To help us design our detection system at Bottle Rock, we wanted to learn more about what a ‘lonely’ rat does, and where it goes, when it enters an area with no other rats. In other words, we wanted to better understand the ‘footprint’ of a rat invasion in space and time, to help ensure early detection and removal.
Between 2011 and 2014 a trial was conducted as part of the Poutiri Ao ō Tāne project, a restoration project located at the Maungaharuru-Tutira catchment, 60 km north of Napier.
This trial sought to compare the efficacy of run-through tunnel traps and standard single-entry trap boxes for ship rats, stoats and ferrets.
Because our detection and removal devices are not designed to target mice, we need to be able to exclude them from these devices to ensure optimal performance of the system.
Here are just a few of the mouse-related challenges we’ve overcome since we began our operations.