PHASE 1, MIRAMAR PENINSULA: SUCCESSFULLY COMPLETED

In November 2023, we announced we had successfully eliminated ship rats, Norway rats, stoats and weasels from the Miramar Peninsula.

Outcomes achieved:

• Successfully eliminated Norway rats, ship rats, stoats and weasels from the entire Miramar Peninsula (approx 1,000 hectares).
• Developed a replicable blueprint for predator free projects working in urban environments, achieving cost reductions of up to 75% per hectare.
• Community biosecurity approach is working and affordable. Stoat incursion response achieved at 3% of the cost, when compared with a similar operation on Chalky Island in Fiordland.
• 91% increase in native bird detections since the project began. Including 141% increase in tūī (project’s indicator species).

• Widespread and equitable participation across the project. This means the ecological and wellbeing benefits, such as rat-free homes or increased wildlife, and potential benefits of participating, such as improvements to people’s psychological and social wellbeing, are not limited to particular sectors of society.

The outcomes of our work on the Miramar Peninsula are a tribute to an epic collective effort.

The project relied on the support of 20,000 locals, and involved almost every business, school and kindergarten, hundreds of volunteers, Predator Free Miramar, technical experts, and our foundation partners Greater Wellington Regional Council, Wellington City Council, Predator Free 2050 Ltd, NEXT Foundation and Taranaki Whānui ki Te Upoko o Te Ika (Port Nicholson Settlement Trust).

Predator Free Wellington’s Phase 1 on Miramar Peninsula was completed in November 2023, and Phase 2 is now well underway. Enjoy this video to gain insights into our project and the systems being used to eliminate target species across the 30,000 hectares in and around Wellington City.

Our work on the Miramar Peninsula marks just the start of a much larger mission. We’ve developed a successful recipe for removing rats and mustelids from an urban environment, and to celebrate this milestone, we have created an easy-to-use, step-by-step blueprint so others can replicate our success.

Importantly, the learning doesn’t stop here. This blueprint reflects what we have learned to date. We know how to effectively remove these target animals, but our next step is to discover how we can do this faster and more economically. We are focused on optimisation, and there will be future versions of this blueprint that incorporate our ongoing discoveries and innovations.

By sharing what we’ve learnt and supporting one another, we can collectively work towards Aotearoa’s ambitious goal of becoming predator-free by 2050.

Read our urban eradication blueprint.

We’ve been tracking birds on the Miramar Peninsula since 2017. This is what we’ve found and why it matters.

Native bird numbers have almost doubled!These results show that when urban predator elimination projects work, they really work.

When you remove introduced predators (rats, stoats and weasels) from an urban environment, it leads to outcomes for biodiversity that are not just a little bit better, but many times greater.

Looking at our indicators

Indicator species are often the first species to be affected by any change in their ecosystem. A positive change may increase the population, while a negative change may cause a decrease.

We chose tūī as the indicator species for our project, as they are not only a distinctive and conspicuous bird species that many local residents appreciate and recognise, but they have also historically responded well to predator control in Wellington City.

Tūī are present in all the major habitat types on the peninsula but appear to be more common in native forest habitat. We saw this particularly around Mt Crawford and in suburbs with greater tree cover and more mature gardens such as in Seatoun and along the eastern bays.

Recolonising birds

Citizen scientists recorded kākā and kākāriki on the Miramar Peninsula on eight and 20 occasions respectively. This is an early sign that these two species are in the process of recolonising forested habitats on the peninsula.

Both species were successfully re-introduced to Zealandia and have been steadily expanding their distribution throughout Wellington City in recent years. Kākāriki also live on Matiu / Somes Island.Local resident Lance Lones spotted this kārearea by Oruaiti Reserve.

Residents have spotted kārearea (NZ native falcon) all over Miramar Peninsula, from native forests to urban areas, even flying over Wellington Airport. The clusters of sightings near Shelly and Worser Bays likely show where several breeding pairs hang out, proving just how adaptable and present these falcons are in the area.

Following the successful elimination of rats and mustelids from Miramar Peninsula, the project has been entrusted to the local community for ongoing biosecurity management. Returning control to the community does not equate to abandonment; rather, it signifies a high-trust collaborative effort.

This community partnership is not only working, but is achieving results at a fraction of the cost.

The Miramar Peninsula biosecurity response depends on a vigilant community of 20,000 residents as our eyes and ears, reporting any sightings via our dedicated 0800 NO RATS number. Additionally, a skilled volunteer team, intimately familiar with the local environment, plays a crucial role in maintaining the area’s biosecurity.

This is supported by our existing detection camera and trap network that can be reactivated as needed and specialist detector dog teams who can respond to incursions almost immediately. Through our Predator Free 2050 networks and foundation partners we also have on-call experts available to offer support, tools and advice.

With this team in place, we can successfully manage incursions in our biosecurity zones, and protect our hard won gains in an efficient and cost-effective way. For the stoat incursion on the Miramar Peninsula, we were able to successfully manage the incursion in not only a similar timeframe to previous predator free island responses, but also at just 3% of the cost*.

In December 2023, a stoat was sighted on the Miramar Peninsula. This was part of our Phase 1 project, where we had successfully eliminated stoats, weasels and rats.

THIS IS HOW WE DID IT

IdentificationWhatsapp volunteer chat messages

On 12 December 2023, volunteer Michelle Willhelm identified a stoat on camera.

Over the following seven months, Predator Free Miramar volunteers checked images weekly, seeing the stoat nine times on camera.

Expert analysis determined we were chasing a lone male stoat which changed our risk profile; a pregnant female would need a different response!

Making decisions

With full support from the Miramar community and our team making great progress in Phase 2, we had some decisions to make. We are finely balanced between moving forward with the project and ensuring we are detecting and removing invaders from areas we have cleared.

Working with our technical partners (ZIP) we made the call to trust our detection cameras and our highly skilled Predator Free Miramar volunteers.

And it worked!

If you were a stoat, where would you go?

Stoats can travel over 70 km when they are finding their own territories. They can also easily swim 3 km between islands. So we were working with a big territory.

Our cameras showed this stoat appeared to have a base in the Northern Bush, but it was also spotted on camera at Oruaiti, Beacon Hill, Maupuia and Lyall Bay. It may have even travelled as far as the city.

We engaged Brad Windust and his stoat scat detector dog Wero to scout the peninsula. They searched for signs of mustelids, food caches, dens, play sites and scat. After scouting the peninsula for a week Wero indicated one site in northern Miramar as a play site and one potential place of interest in Lyall Bay.

Brad’s gut feeling was this stoat was only a visitor to Miramar, explaining he would have found more scat if it was living there.

The pink lines show Brad and Wero’s track logs. The red markers indicate stoat scat and play site.

Bringing in the experts

To support our response, we enlisted John Bissell from Backblocks Environmental Management to share his expertise. This empowered and equipped the Predator Free Miramar volunteer crew to lead the response.

John uses a mix of science, hunting and gut instinct. He specialises in targeting one animal in a large landscape.

John advised the crew: “The stoat is not just going to blindly walk into a trap just because it happens to be there… You have to think like a stoat.”

And that called for a change in strategy and mindset.

Scorching Bay: Stoat scat site and play site found by Brad and Wero (NB. traps were added after the sighting)

Leaning in to the hunt

The skills of the Predator Free Miramar volunteers extend so far beyond basic trapping. They call themselves the ‘flying squad’ and are creative problem solvers who volunteer most Sundays.

Every weekend since the first stoat sighting in December, volunteers were rebaiting and moving traps near to where the stoat was seen. But there was an underlying sense of frustration after months without success.

Following John’s visit, the volunteer trappers had renewed confidence and a deeper awareness of what was needed to catch this stoat. They knew it was a fool’s errand to manage hundreds of traps; instead they needed to do a handful of traps really well. They chose premium sites that were freshly baited and beautifully presented.

Years of trapping rats meant they knew the landscape intimately. Features like ridges, streams and roads guided their thinking. Bush edges and fence lines hid the stoat from predators like kārearea (NZ falcons) and kahu (hawks): these were good places for traps.

The trappers used heaps of fresh red meat (beef, mutton and venison) and stoat bedding. The tennis ball-sized bedding was a visual lure, with the idea that if the stoat wasn’t hungry it might be curious about finding a mate or fighting off another stoat.

A successful catch

After 207 days and 755 hours of volunteer time, the Predator Free Miramar volunteers caught the stoat in trap number BT302 (north of Massey Memorial). It was lured with aged venison and male stoat bedding.

The trap was cleared by Gerard Hutching and Mike Arnerich, two of Predator Free Miramar’s regular weekend trappers. The trap itself had been moved several metres into a better position six weeks prior by Mike and John Herrick and the new site (and lure) proved to be a winner.

In the end, Dan Henry (Predator Free Miramar Lead) believes it was a series of small decisions that made the difference.Story in The Post celebrating the volunteers catching the stoat.

“It wasn’t a super stoat that’s too smart. It was catchable, with effort, persistence and creativity,” said Dan.

The volunteers were given the freedom to lead the response and that was part of the appeal, along with the mateship and a sense of community.

This won’t be last stoat we encounter but we are pleased to have this one dealt with, and it provided a perfect testing ground for our community biosecurity response. We got the result and are defining a new model for biosecurity response at a fraction of the cost.

What we now know

The invading stoat was sent for genetic testing at Manaaki Whenua, revealing that the animal was a young male, born in September 2023. Likely dispersing in search of territory.

Genetic sequencing indicates that this stoat is most closely related to one previously caught near Makara Beach, followed by another from Tongue Point. These relatives are not from the same litter or parents, meaning they are more distantly related, like cousins or grandparents.

These findings highlight a significant geographic spread, as stoats are known for their ability to traverse considerable distances. Importantly, now that we know the likely origin, we can confirm that the stoat did not swim across the harbour to reach the peninsula; rather, it entered by land. Understanding these details helps us adapt and improve our biosecurity response systems.

*Cost savings were compared to a recent effort to remove a stoat from Chalky Island in Fiordland, which cost almost $500,000 NZD.

The Miramar community are essential for spotting rat invaders; they are our constant eyes and ears on the ground. Reporting possible rat activity is quick and easy, and for residents of Miramar it’s a natural expression of kaitiakitanga (guardianship).

112 Miramar residents reported potential rat activity between January - September 2024.Between January and September 2024, residents reported 112 cases of potential rat activity. While the vast majority of these turned out not to be rats, we were grateful for the reports.

For our team, finding a rat in a cleared area is no reason to panic. We expect some individuals to reinvade and we use the same approach that removed rats in the first place. This is the system working and we are massively thankful to the community for helping us to keep Miramar Peninsula rat and mustelid free.

Rapid rat response

We take all rat sightings seriously, and aim to respond to every report within 24 hours.

There is no one-size-fits-all response to returning rats, but we generally get rat detector dog Rapu and handler Sally on the case.

If Sally and Rapu verify there is a live rat present, we then send in our Capture team.

The Capture team are our incursion specialists and will create a response area with a 150 metre buffer from the detection. Managing the response involves analysing camera footage, re-engaging with residents, servicing traps and bait stations and placing out additional detection cameras and chew cards over a wider area.

Response areas are treated much like rat hotspots, where the data is critically assessed after every visit and the servicing frequency, area and regime adjusted accordingly.

We’re always watching

Can we still call these areas ‘predator free’? Absolutely. We know rats or stoats can slip back in and we have a proven system to detect and remove them. No one is looking harder than us. Wellingtonians also fully support having a predator free city and their reports are essential. We are confident there are no rats in biosecurity areas and when we occasionally find one has snuck in, the Capture team swoops in to take care of it.

Read more about our Capture Team here.

Everyone realises we need to be vigilant, keep monitoring and report sightings so we can mobilise to catch the rat or stoat.

Sue, Predator Free Miramar Volunteer

Residents know to call 0800 NO RATS if they see any rat activity.

DNA unravelling rat populations

Genetic sequencing data of the last remaining rats on the Miramar Peninsula has provided insights into the local rat population, and a snapshot into the effectiveness of our biosecurity efforts.

This genomic study, the first of its kind in a New Zealand elimination project, aimed to uncover the genetic relationships among the last remaining rats on the Miramar Peninsula. By mapping their genes, we are able to distinguish between local rat survivors and new invaders, making our biosecurity efforts more targeted and efficient.

What we did

Our container of rat tail snips for DNA testingThis was a genomic study, which means it explored the genes and DNA of a plant or animal. From mid-2022 to late 2023, we caught the last ship rats on the peninsula. We collected a short piece of each rat’s tail and sent these to Andrew Veale at Manaaki Whenua Landcare Research. The 74 samples gave 30,000 genetic markers, which helped Andrew and the team create a detailed map of the population.

What we found

Their work showed two distinct groups – rats on Miramar Peninsula were genetically different from those in Rongotai and Lyall Bay. We have a buffer system of traps, cameras and bait to prevent rats returning to the Peninsula. Looking at a genetic level showed that our system worked. The final ship rats we caught during our elimination were Miramar rats: they hadn’t snuck in from other areas.Their work showed two distinct groups – rats on Miramar were genetically different from those in Rongotai and Lyall Bay. We have a buffer system of traps, cameras and bait to prevent rats returning to the peninsula. Looking at a genetic level showed that our system worked. The final ship rats we caught during our elimination were Miramar rats: they hadn’t snuck in from other areas.

What it means for our project

We now know what a ‘Miramar rat’ looks like, genetically. When we catch rats on the peninsula in the future, we can compare its genes to our existing data to learn if it was an invader or had avoided us all along. In the past we’d have to guess where rats came from; now we know. As we move across the city, we’ll build a genetic map of rats from different areas.

This study also confirmed what we know about rat behaviour. Normally, closely-related rats stay close to each other. When rat populations are incredibly low, individuals will travel far searching for mates. This means when we find a lone rat, we need a wide buffer to catch other individuals that could be up to 2km away.

We’ll use this data to help refine how we work. This will be especially helpful as we move into later phases of the project, which cover large and challenging areas. The more we understand rat populations, the quicker, smarter, and more cost-effective our path to a predator-free city will become.

In our Phase 2 project, the focus is on optimisation. We have proven we can successfully eliminate rats and mustelids in an urban setting, our next challenge is to accelerate the process and reduce costs.

This is the necessary step to achieve the ambitious Predator Free 2050 New Zealand goal.

What’s involved? This second phase involves 14 suburbs from Kilbirnie around to Ōwhiro Bay and up through to the CBD. It is home to approximately 60,000 residents, and includes Wellington Zoo, Government House, Massey University and Wellington Regional Hospital.

The full Phase 2 rollout will see the installation of 2,596 traps, 8,488 bait stations and more than 500 detection trail cameras.

How many rats are out there? It’s a tough question to answer as it’s not just about counting rat catches: we also consider bait station interactions, chew card monitoring and data from our detector dog team. Based on our findings from our work in Hataitai, we estimate there’s at least one rat for every two people.

How fast are we moving? In a strategic shift from our approach on the Miramar Peninsula, Phase 2 has been divided into 32 distinct zones. Splitting the area helps us target our approach more effectively based on the habitat and land use.Map showing the 1400-hectare Phase 2 project area, divided into Districts (A - F) and Zones (numbered).

We use a ‘rolling front’ approach: beginning our operations in one zone (usually the most easily defendable from reinvasion) and progressively moving across the landscape, eliminating rats and mustelids zone by zone until each district is completed. This creates a moving front line, with some zones actively being worked on and others already cleared and protected from reinvasion. We can open new zones as we finish the previous ones and free up staff. Think of it like puzzle pieces fitting together; over time, the cleared area will grow until the entire phase is complete.

This approach has been successful; it allows us to work intensively in a small area to reach elimination without biting off more than we can manage at one time. Spreading ourselves too thin over too large an area was one of the reasons ship rats weren’t eradicated from the Miramar Peninsula on the first attempt. While we can suppress rats on a large scale, completely removing them is much harder. The size of each zone will depend on factors like team size, resources, geography, and urban development.

On average we can halve the rat population after two services (four weeks), and you can see from the examples below how quickly we are getting the rat numbers to almost zero.

These charts illustrate the reduction of rat populations in our Hataitai zones over time, based on fortnightly services by our field team.