Great Island.

Trapping to protect island sanctuaries

Great Island.

Trapping to protect island sanctuaries

In Fiordland National Park New Zealand, the sea meets the land in a maze of inlets and islands covered in lush, untouched rainforest. Remote and hard to access, many of these islands host conservation projects in a bid to save critically endangered endemic species. Their isolation, however, doesn’t prevent threats: from the mainland, possums, rats, deer and stoats will take any chance to reach these fragile sanctuaries in their quest for food.

Nested in Taieri/Chalky inlet and surrounded by relatively calm waters, Great Island is at the core of one of these conservation projects: it relies exclusively on Goodnature A24 traps to keep stoats from reaching nearby Chalky island.

A network of strategic and vulnerable islands

The largest of the Taieri/Chalky Inlet islands, Great island acts as a skipping stone for stoats on their way to nearby Chalky Island. Chalky has been free from mammalian predators since 1999 thanks to conservation efforts. It is home to the endemic Te Kakahu/Chalky Island skink and is used as a translocation area for several critically endangered bird species, notably the kakapo, a flightless ground-dwelling parrot.

The pest-free sanctuary is located 1km away from Great Island via Passage Island, well within stoats’ 2km swimming reach. Chalky Island relies on Great Island’s trapping success to front the threat of stoat invasion that would annihilate all conservation efforts.

Goodnature started working on the Great Island in 2017 with the Department of Conservation, and became the guardian of the island in 2018. The 7.36 km² island is protected by a network of 230 A24 traps serviced twice a year by a team of Goodnature employees, Department of Conservation workers and volunteers from all over the world. The trapping network has been designed for stoats: the bait is a stoat lure and the traps have been laid strategically to ensure they will be everywhere where stoats might go.

Laying the original network required clearing paths through the dense forest and installing the traps in wet conditions. The hard work paid off: two days following the original trap deployment, 17 stoats were caught: 10 males, 7 females (source). To date, 50 stoats have been trapped and none have been recorded on Chalky Island.

The stoat trapping network is the first and most crucial step in securing the island. The next step for Goodnature is extend the network of A24s to target rats to control their population on the island without the use of toxins.

The right trap for the job

There are a few reasons our A24 traps are perfect for the job - after all, they were designed for it.

Goodnature traps self-reset 24 times before they need servicing every 6 months. This is crucial as re-baiting and servicing missions are dependent on weather and sea conditions. The remoteness of Great Island means traps are only serviced twice a year. By comparison, traditional traps perform one kill at a time, and once set off, they need to be manually reset after each kill.

Stoats have been known to travel up to 70km in two weeks: enough to visit the whole island faster than traditional traps can be reset. Constantly armed, Goodnature self-resetting traps ensure the area remains fully protected between missions.

The ease of deployment of the A24 means a single person can transport thirty traps in a backpack, enough to cover a whole trap line in less than a day.

Great Island is remote, covered in dense vegetation, and wilder than your classic tramping track: paths are rough to non-existent, the ground is muddy with steep sections. The ease of deployment of the A24 means a single person can transport thirty traps in a backpack, enough to cover a whole trap line in less than a day. Once the traps are installed, all they need is a top up of lure and gas canisters every six months.

A smart island

In January 2020, our team deployed Chirp, Goodnature’s Smart Trapping technology, onto all traps on the island to monitor trapping activity and learn about stoat behaviour. The installation was straight forward: along with refilling lure and changing gas canisters, the team had to fit a Chirp cap on every single trap of the network and pair them with their smartphone. The process was fast but necessitated extensive planning ahead, with each cap ready to be paired and geolocated accurately.

Chirp records the time, date and air temperature at the time the trap was triggered, giving precious information such as the number of stoats and rats removed from the island, their location and the conditions in which they were looking for food. Looking at the interactive map on the Chirp App provides an insight into rodent activity over the island. Everyone who has Chirp on their phone can see this data and view the trapping progress down in Fiordland.

Along with tracking tunnel monitoring, Chirp data is collected while servicing trap lines and transferred to the trappers’ phones via Bluetooth. The wireless, close range technology coupled with most phone’s GPS system is essential for places with no wifi or cell phone reception, and provides a reliable way to retrieve the data with minimal effort.

In August 2020, six months after Chirp was deployed onto the island, the Goodnature team went back to collect the data: the traps have humanely killed a thousand pests so far.

The latest bird sightings indicate that the bird population has doubled since the network was installed, bringing hope that maybe one day, in our lifetime, we will be able to hear the dawn chorus again, with songs of mohua, kākāriki, tīeke, toutouwai and little spotted kiwi rising from the emerald forests of one of the world’s most remote sanctuaries. In the meantime, Goodnature traps will keep on working in the background to ensure the kakapo on Chalky Island remains out of reach from island hopping stoats.

Learn more about Chirp.

Chalky Island at the entrance of Taieri/Chalky Inlet

Left: Dense native forest on Chalky island - Right: Boat Cove, Chalky Island

Yellowhead/mohua populations are thriving with stoat and rat control.

Left: Toutouwai/South island robins are curious and will land within reach of trappers every time they service a trap. Right: Seal on Chalky island.

Great Island is one of many islands that act as skipping stones for Stoats on their way to pest-free Chalky Island. Each dot represents a trap.

The team of Goodnature employees and volunteers on Great Islands.

Roy and Chris from Goodnature, preparing the Chirp caps before deployment on Great Island.

The mainland as seen from Great Island. Located only 80m away at the closest, it offers easy access to stoats, who are good swimmers.

Chirp being retrofitted to a Goodnature A24 trap. The process is fairly simple and was done while refilling the lure and changing the gas canister.

A tracking card displaying mouse and rat activity on great island over the a 6 month period. A bit of peanut butter sits in the middle of an inked pad. Rodents leave footprints once they exit.

Goodnature A24 trap with Chirp. The technology will keep track of the trap activity.

Taieri/Chalky Inlet

Chalky Island at the entrance of Taieri/Chalky Inlet



Left: Dense native forest on Chalky island - Right: Boat Cove, Chalky Island


Yellowhead/mohua populations are thriving with stoat and rat control.

Left: Toutouwai/South island robins are curious and will land within reach of trappers every time they service a trap. Right: Seal on Chalky island.

Great Island is one of many islands that act as skipping stones for Stoats on their way to pest-free Chalky Island. Each dot represents a trap.

Roy and Chris from Goodnature, preparing the Chirp caps before deployment on Great Island.


The team of Goodnature employees and volunteers on Great Islands.


The mainland as seen from Great Island. Located only 80m away at the closest, it offers easy access to stoats, who are good swimmers.

Chirp being retrofitted to a Goodnature A24 trap. The process is fairly simple and was done while refilling the lure and changing the gas canister.

A tracking card displaying mouse and rat activity on great island over the a 6 month period. A bit of peanut butter sits in the middle of an inked pad. Rodents leave footprints once they exit.

Goodnature A24 trap with Chirp. The technology will keep track of the trap activity.


Taieri/Chalky Inlet