The Forest Bridge Trust – Stoat monitoring

Wildlife monitoring cameras, also known as trail cameras, are increasingly being used by The Forest Bridge Trust (TFBT) as a tool to study and monitor mustelids (stoats, ferrets and weasels). The trust’s ecology and biodiversity advisor Virginia Moreno recently deployed 116 lured trail cameras across the rohe to learn more about the impact stoats are having on the ecosystem, and determine the effects that predator control and trapping efforts have had on stoat populations. Trapping catch data is measured on the TrapNZ App which gives us the number of stoats removed. We are now looking at measuring the abundance of stoats that have survived trapping.

Stoats were introduced in the late 19th century to help reduce the rabbit population. They quickly established themselves as a significant predator of many native bird species, bats, lizards and invertebrates.

Stoats are clever and cunning creatures. They hunt day and night, moving quickly checking every burrow and hollow they come across, and will kill more than they need to eat. Ground-dwelling birds such as young kiwi, dotterel/tūturiwhatu and black-fronted terns/tarapiroe are easy targets. Stoats are particularly effective predators because they can kill kiwi chicks that weigh four or five times more than themselves. Birds that nest in tree hollows such as kākā and kākāriki are also vulnerable. According to Save the Kiwi, stoats are the main reason why 95% of kiwi hatched in the wild die before
they reach breeding age.

To date, TFBT has mustelid control measures over 28,000 hectares, which is halfway to our goal of 54,000 hectares by June 2025. We had a great response from the community when we started to seek out landowners who might be happy to have trail cameras on their properties. Many property owners were already trapping on their land and are regularly recording their catch data via the TrapNZ App. We know from this data that for the last quarter of last year (Oct-Dec), 68 stoats were caught in the rohe.
Over the last month, we have been collecting data to obtain a camera-trap index (for example the number of stoats detected per camera per day) and occupancy (the percentage of cameras with stoat detections).

A total of 74 cameras are within mustelid-trapped areas and 42 in non-trapped areas, which will allow us to look at differences in relative abundance and occupancy between treatment and non-treatment areas. Cameras in non-trapped areas will provide baseline data so we can make comparisons after traps are introduced.

The results of the stoat monitoring project will better inform us of the effectiveness of our trapping efforts and whether we need to adapt trapping methods. It’s a long, ongoing battle but eventually, we hope that more and more people in the community will enjoy the benefits of fewer predators in the landscape and increased backyard bird song.

Info: www.theforestbridgetrust.org.nz