Stoat Monitoring Project taking place across the rohe

Wildlife monitoring cameras, also known as trail cameras, are increasingly being used by The Forest Bridge Trust as a tool to study and monitor mustelids (stoats, ferrets, and weasels). The Trusts Ecology and Biodiversity Advisor Virginia Moreno has recently embarked on a stoat monitoring project, deploying 116 lured trail cameras across the rohe to learn more about the impact stoats are having on the local ecosystem and determine the effects that predator control and trapping efforts have had on stoat populations in the Rodney area.

“We measure trapping catch data on the TrapNZ App which gives us the number of stoats removed and now we want to measure the residual stoat abundance (the abundance of stoats that survive tapping)” explains Virginia.

Stoats were introduced to New Zealand in the late 19th century and brought over from England to help reduce the rabbit population. However, stoats 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, New Zealand dotterel/tūturiwhatu and black-fronted terns/tarapiroe are all 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 to stoat incursions. According to Save the Kiwi stoats are the main reason why 95% of kiwi hatched in the wild die before they reach breeding age. Without stoat control, kiwi could be lost from the wild within two generations.

Predator control has been a focus of The Forest Bridge Trust since its inception in 2014. The Trust has a vision to build a connected landscape of healthy forests and flourishing indigenous wildlife from the Kaipara Harbour to the Pacific Coast, a haven for native birds and an opportunity for the community to become involved with the New Zealand Predator Free 2050 initiative. To date, The Trust have mustelid control measures over 28000 hectares across the rohe. Being halfway to their goal of 54000 hectares under mustelid control by June 2025, the Trusts Ecologist felt now was a good time to investigate and compare stoat relative numbers before and after trapping.

TFBT had a great response from the local community when they started to seek out landowners who might be happy to have trail cameras placed on their properties. Many property owners were already trapping on their land and are regularly recording their catch data via the TrapNZ App but knowing how wily stoats can be there was a keen interest to help the Trust find out just how effective efforts to reduce the stoat population had been over the past few years. We know from the recorded catch data of the last quarter of 2022 (Oct-Dec) that 68 stoats were caught in the rohe, but the question is, how many more are out there that we aren’t catching?

To help answer this question The Forest Bridge Trust’s Predator Control team set up 116 lured trail cameras across several properties.

“We will be collecting data for one month (mid-March to mid-April) 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)” explains Ecologist Virginia Moreno. “74 cameras are within mustelid-trapped areas and 42 in non-trapped areas, this allows us to look at differences in relative abundance and occupancy between treatment and non-treatment areas”.

“Data collected from cameras in non-trapped areas will serve as a baseline to compare with after traps are introduced to these areas, allowing us to compare stoat relative numbers before and after trapping. The results of the stoat monitoring project will better inform us of the effectiveness of our current trapping efforts and whether we might need to adapt trapping methods if necessary (for example if pockets of high activity within trapped areas are detected this could translate into a more intensified trapping in this particular area)”.

The Predator Control team will be retrieving the cameras over the next few weeks and then the process of analysing the data will start. Results will be shared with landowners and the wider restoration and scientific community so we can all learn from this study.

The more that we can learn about the behaviour of stoats in our rohe the more measures we can put in place to catch them and better protect our native birds. With fewer stoats to contend with our native birds have a better chance to thrive and raise young. 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.

If you are interested in learning more about The Forest Bridge Trust and maybe getting involved with predator control in the Rodney District, please see the TFBT website