Fiordland Kiwi Diaries: Resolution Island Trapping

Department of Conservation —  11/08/2018

We caught up with Tim, a ranger on the front lines of the Save Our Iconic Kiwi initiative. This is the fourteenth in a series following the work he’s doing to save the Fiordland tokoeka (kiwi). Tim and his team have been studying the population of kiwi at Shy Lake to find out how to best protect them from predators like stoats. They have captured a number of kiwi and put transmitters on them, and are now monitoring them through the breeding season to find out how well the adults and chicks survive without pest control. 

A change of scene on the Fiordland Kiwi Diaries this month. We haven’t been in at Shy Lake much, but I was lucky enough to get a spot on the Resolution Island trapping trip in July.

Fiordland coast.

Fiordland coast

Resolution Island, in Dusky Sound, is huge – at 21,000 hectares, it’s the fifth biggest island in the main New Zealand archipelago. Although much of the topography is a bit gentler than the nearby mainland, it’s still an imposing wilderness of weathered mountains and rocky coasts, swathed in temperate rainforest. It has an illustrious conservation history: over a century ago, pioneering conservationist Richard Henry became the government caretaker for Resolution Island. Seeing the onslaught on native birds posed by introduced mammals such as stoats, he embarked on a harsh and isolated existence in Dusky Sound, transferring kiwi and kākāpō to Resolution in a small sailing dinghy. Sadly, after years of graft, stoats swam to Resolution and established a population. The kākāpō were wiped out but the kiwi clung on.

Anchor Island and Dusky Sound from Resolution Island.

Anchor Island and Dusky Sound from Resolution Island

Today, Resolution is once again the centre of an ambitious conservation programme. The island has stoats, mice and deer, but is free of possums, rats and other mammals. The steep ridgelines and shadowy valleys bear a latticework of tracks, and every hundred metres a DOC 150 trap waits patiently for a stoat. Nearly two and a half thousand traps in all, plus another thousand on other islands in Dusky and the mainland coast, and many more planned. Checking and rebaiting these is an epic task that takes over a week for a dozen people every November, January and July, not to mention the meticulous planning by ranger Pete and his team. Stoat numbers have been reduced to low levels, but there are still some breeding females out there; and to make things worse, in a beech mast year, a stoat plague on the mainland means a wave of new invaders swims the channel to wreak havoc on the recovering birdlife.

Temperate rainforest, Resolution Island.

Temperate rainforest, Resolution Island

For me, this project has resonance because Resolution and nearby Long Island are currently the only places where southern Fiordland tokoeka, the subject of my Save Our Iconic Kiwi project at Shy Lake, are protected in any numbers. Northern Fiordland tokoeka receive protection from trapping or 1080 in strongholds like the Murchison Mountains and Milford track, but for the southern taxon, Resolution is it. That’s one of the main reasons why we chose to start Save Our Iconic Kiwi work where we did: to control stoats over a big block of hitherto unprotected southern Fiordland tokoeka territory. Resolution sits just off the western extremity of our planned pest control area, and so we expect that our planned aerial 1080 operation in 2019 will have an additional benefit: not just to protect kiwi in the control area itself, but to prevent the influx of stoats swimming over to Resolution.

Kidney fern, Resolution Island.

Kidney fern, Resolution Island

To begin the trip, it’s up bright and early for a quarantine check, going through all our gear with a fine toothcomb to remove any seeds, insects or other potential stowaways. Then it’s onto the bus, a charter boat across Lake Manapouri, another bus to Doubtful Sound and finally onto the MV Southern Winds, a boat dedicated to Fiordland conservation work that will be home for the next week for nine of us. A further four are due to helicopter in tomorrow to stay in small huts on the island.

MV Southern Winds in Dusky Sound.

MV Southern Winds in Dusky Sound

The trip down Doubtful Sound and the Fiordland Coast is wonderful: sheer faces dropping deep into the sea, wheeling albatross, small islands dripping with vegetation and, as we reach Dusky, a pod of bottlenose dolphins leaping from the water. We anchor in a quiet cove. The morning dawns fine and I’m excited to get up and into it. I’ve spent years looking at Resolution from nearby Anchor Island in my former life as a kākāpō ranger, and I’m looking forward to finally exploring some of those peaks and ridges. I load up my pack with trapping kit, safety gear, food, the essential flask of tea, and the even more essential five dozen eggs. Pete drops me on a beach and I bash up through the forest until an orange triangle and a faint ground trail show that I’ve hit my trap line.

Buller's albatross.

Buller’s albatross

There’s a nice meditative rhythm to this trapping business. Walk, stop, unscrew the box, safety clip on the kill bar, trigger the trap, biff out the old egg and rotten meat, add the fresh egg and meat, reset the trap, screw the box closed, make a note, walk, repeat. On this island, it’s faster and much more pleasant than on the mainland because you aren’t catching much – today I only had one manky stoat to chip off the trap with a paint scraper and bag up for DNA analysis. But that’s one less stoat running around killing kiwi chicks come September.

Trap box being rebaited.

Trap box being rebaited

With fresh legs and fine weather, the 900 metre pull up the hill feels like a breeze. All of a sudden, I break out of the bush to a glorious panorama of blue sea, green islands, snowy white peaks. Living the dream. I’m halfway through my traps by lunch time and feeling good – but naïvely so, as I embark on the notorious “rollercoaster” section of steep climbs and drops. The sun is setting as I meet up with volunteer Becky and ranger Lyndsay at the end of their trap lines, and together we pick our way down in the darkness, on weary legs and aching knees, to a welcome hot dinner on the boat.

Volunteer Becky and ranger Lyndsay on the evening descent to Dusky Sound.

Volunteer Becky and ranger Lyndsay on the evening descent to Dusky Sound

Next day I get to drive the dinghy as we buzz around the myriad islands, my two trappers leaping onto rocks to service the traps, all of us cocooned in waterproofs against rain and waves. On the third day’s trapping, the weather turns as I head up through dripping forest to stay in a small hut on the tops. Day four looks a bit better as I head out on a long ridge walk… but a couple of hours later, I’m battling through drifts of driving hail as thunder booms on nearby peaks. Down in the valleys, the unexpected severity of the storm forces several trappers to turn back as trickling creeks, not even marked on the map, become raging torrents. Pete has to take a detour of several hours to get around his flooded creek, and with fading head torch he finally wades through the shallows to the waiting dinghy, ready to whisk him away to the sanctuary of the boat and a very welcome hot shower. From our sheltered anchor, I hear a male kiwi calling from the darkness – an evocative reminder of why we’re here.

Last few dinghy traps before nightfall.

Last few dinghy traps before nightfall

Another day’s boat trapping follows. I’m struck by the huge difference in catch rates between the island and the mainland. I’ve had just three stoats from 206 traps walking around Resolution, but on the mainland coastal traps I’m getting a stoat every two or three traps. These traps are on the same big peninsula as my Shy Lake study site – no wonder those kiwi chicks are in trouble. But it goes to show that the ongoing efforts on Resolution are working. I reckon Richard Henry would be stoked.

Sorting gear on the way home.

Sorting gear on the way home

This is the fourteenth in a series of posts about Tim’s work, follow the Conservation Blog to keep up to date on his progress.

6 responses to Fiordland Kiwi Diaries: Resolution Island Trapping

    Bevan Allchurch 22/11/2018 at 10:00 pm

    Tim, Nice to meet you in person on a recent Discovery Expedition trip to Dusky Sound. A beautiful part of NZ and a great conservation project to maintain and rebuild the biodiversity of Fiordland. Keep up the great work!


    brilliant, thanks for taking the time to share!

    Brooke Smith 11/08/2018 at 4:20 pm

    Awesome work! This is a really good insight.



    Are there any costings done for this programme?

    It is a very impressive record of achievement but with 21,000 hectares to cover and the operation continuing forever, it does make me wonder what the cost is of other options requiring less labour input.

    * For example, with PAPP now registered for aerial application might the helicopter application of PAPP every 1-2 years be another effective way of controlling stoats.

    * Also how low a stoat population can be achieved if there was regular aerial 180 operation on another location-say Southern Fiordland where we just accept that there will eventually always be re-invasion. At what level of stoat numbers does it become possible for kiwi to reproduce/

    Kind wishes,
    Gerry McSweeney

      Tim Raemaekers 20/08/2018 at 4:24 pm

      Hi Gerry, thanks for your questions.

      To begin at the end, we are planning just what you suggest: the peninsulas either side of Wet Jacket Arm in Fiordland are slated for 1080 control under the Save Our Iconic Kiwi project. The differences between that area and Resolution Island account for why we are using different approaches in these neighbouring sites.

      Resolution Island has an ongoing intensive sustained stoat control programme using a trapping network that maintains stoats at very low densities. This has allowed the recovery of rock wren and fern birds and the reintroduction of mohua, robins and tieke. Kaka, kea and tokoeka are not monitored but anecdotally are doing well.

      The regular migration of stoats from the mainland means that relying on intermittent control on the island would not be an appropriate approach. We are exploring how to reduce the stoat density on the island further, how to reduce immigration and improve stoat intercept.

      One of the reasons that we haven’t used aerial toxin on Resolution is that there are no rats or possums. There are often high mouse numbers. With only mice as a vector to transmit 1080 cereal pellets to stoats, we would expect a decent knock down of stoat numbers but also potentially survivors, and we wouldn’t affect immigration from the mainland at all. It would also be a very expensive area to control stoats via aerial toxin on Resolution, as it would have a long ferry time from the nearest loading site.

      The budget for Resolution for this year is about $188,000 plus maybe $60,000 boat costs – this budget includes many other islands in Dusky Sound. That gives an annual cost per hectare of under $11. That is actually a very good cost, as the island nature of Resolution means stoat densities have now been reduced to 0.002 stoats per hectare per year. Similar mainland programmes in Fiordland currently cost more per hectare and deliver higher densities of stoats. As a result, Resolution is well on the way to fulfilling its promise as a stronghold for stoat-sensitive native species.

      The projected cost for the planned Shy Lake 1080 operation is around $35/ha (although there is plenty of work still to do on this); so very roughly, in financial terms you would get 3-4 years of trapping on Resolution for one 1080 job. But trapping there means stoats are suppressed every year, whereas with 1080 they would probably start building up or invading from the mainland before 3-4 years was up.

      3-4 years is not too different from how often a beech mast year hits, and is also the frequency of 1080 operations in the Tongariro Kiwi Sanctuary. The area planned for the Shy Lake operation, however, is mostly even more rugged and therefore more difficult to trap than Resolution, has no existing infrastructure like tracks, and is closer to loading sites, and so is more suited to an aerial job. Because it has rats, we get a full ecosystem benefit by using 1080, whereas a trap network targeting stoats would have little impact on rat numbers.

      Your question about how few stoats we need for kiwi to reproduce is a good one. Answering it for Fiordland kiwi in the Fiordland habitat is one of the aims of the Shy Lake study – the breeding biology of the kiwi and the predator ecology of the habitat is different to the North Island, where more kiwi research has been done. We know that in the Murchison Mountains in Fiordland, trapping has made a significant difference to kiwi survival. We’re expecting that 1080 every few years in areas such as Wet Jacket Arm will give the kiwi enough respite for the population to increase, but just how often we would need to use it is one of the things we need to find out.

      PAPP is still subject to stringent legal restrictions and not ready for aerial use in terms of the delivery method. At the moment, PAPP is used as a paste mixed with mince but this is not suitable for aerial use. Research is underway to find a way to distribute it in a pelletised form that is palatable to mustelids. We’re several years at a minimum from using it operationally. If and when this happens it will be a big breakthrough, and I would personally expect that we would see it used for stoat control in many places. Whether that happens on Resolution, and whether in tandem with trapping, or in place of it, remains to be seen.

      I hope that answers your questions,


        Great update Tim – very interesting. Certainly seems trapping is the best option for Resolution.
        Cheers Jim