The Miramar Peninsula project has enabled a proof of concept for an urban eradication. We now have a template that can be replicated nationally. We have successfully eradicated weasels and Norway rats and we have almost eradicated Ship rats.

Importantly, Miramar residents will tell you it’s working - you can hear and see the difference. We are not just halting decline, we are seeing the bounceback. Our native birds have increased by 33% on the peninsula and wētā numbers have doubled since we started the eradication.

The last weasel was caught in January 2021

Learning log - sharing our tips, tricks and some of our learnings

Palatability of pre-feed for mustelids

Problem: Initially we used long life rabbit lures, but then found research to suggest that these were not palatable for mustelids meaning they wouldn’t return for a second feed which was critical for habituation prior to making the traps live.
Description: Switched to fresh rabbit meat to pre-feed locked open traps which were re-baited every fortnight.
Learning: It took a lot of effort to keep up with the supply of fresh meat but through collaboration with Greater Wellington Regional Council we were able to do this and give the regional rabbit population a good towelling.
Outcome: Fresh rabbit used to pre-feed traps, zip tied open so the base plate behaves normally over a period of 2 months worked really well to habituate weasels before all traps were livened up simultaneously. The majority of weasels were eradicated over a period of 4 weeks.

Ability to confirm bait take as rat

Problem: In order to ascertain whether our team were accurately distinguishing rat bait take from mice take we developed bespoke ink tracking cards to install in bait station entrances.
Description: 10,000 pieces of card were cut with a waterproof membrane over the centre and each card was individually inked in situ so it was as fresh as possible.
Learning: Field teams were able to collate perceived rat bait take with actual footprints to calibrate their interpretation of results.
Outcome: A useful tool for us to be able to further refine our accuracy in determining and reporting rat bait take to inform operational planning. Note, this photo shows mice footprints.

Monitoring for rat presence

Problem: Chew cards are a great tool for ease of deployment but we wanted to make sure they had the highest degree of efficacy possible. Research told us that fresh, quality peanut butter improved interaction rates.
Description: Made our own chew cards with top of the line nut butters kindly supplied by our partners at Fixx and Fogg in Wellington - thanks heaps! This guaranteed fresh chew cards.
Learning: Premium nut butters with high nut concentrations are far more aromatic and improved interaction rates.
Outcome: Continued to deploy all of our own hand filled chew cards which are proving to be a very effective detection tool in the urban context.

Deploying chew cards at scale

Problem: Hand filling chew cards at scale to get thousands of them into the field was proving to be a challenge.
Description: A fantastic retired builder and Predator Free Miramar volunteer (John Herrick) was unable to check traps because of an injury, so he offered to assist with chew cards instead. He designed a crafty chew card press capable of holding 280 chew cards at once that can be slathered with fresh nut butters direct from Fix & Fogg’s factory.
Learning: Simple but super effective way of producing fresh chew cards at scale to keep up with operational demands.
Outcome: We now have three presses and would be lost without them.

Improving interaction rates with traps in protective boxes.

Problem: A small number of rats will not go into lethal devices, which is a problem when you’re aiming to get the population to zero.
Description: Setting traps in three sided boxes that were staked to the ground. Not having a base on the boxes provided a natural and consistent surface for rats to enter.
Learning: Created the perfect indoor/outdoor flow for trap boxes to cater for rats that wouldn’t enter traditional devices.
Outcome: Technique only used to target individual rats post knockdown phase where they are not interacting with other traps and bait stations. Haven’t fully evaluated the efficacy at this point because the sample size is so small but early camera data is showing promise.

Accessing steep habitat

Problem: Unable to put field teams into incredibly steep cliff terrain which is ideal rat habitat.
Description: The field team designed and built boomerang bait stations capable of keeping bait secure in the device and being lowered off the side of cliffs for later retrieval.
Learning: Getting lethal devices into all rat habitat is key to the eradication goal. We needed to trial different weighting systems to hold stations in place to provide for easy access and not put animals off.
Outcome: Evaluation is still in process, we have had some good early success in extreme terrain.

Recycling detection tools

Problem: How can we re-use chew cards that have no chews once rat numbers are really low to keep costs down and minimise waste.
Description: Lined up chew cards in the filling press and used an air compressor to blow them out, ready for the next slathering in fresh peanut butter.
Learning: Proved to be a bit fiddly but the technique is constantly being refined.
Outcome: Reduced costs and the big win is from minimising waste. The idea had the benefit of re-deploying chew cards that had already been in the field meaning they were already weathered and not look or smell new to rats potentially impacting interaction rates.

Testing proof of freedom

Problem: How to lure a remaining rat to a camera in an area we think has been successfully eradicated.
Description: Developed a swag of reusable screw top plastic pots filled with peanut butter that have a small hole drilled in the side to slowly leach oil and peanut butter in front of a camera.
Learning: Provided a cheap longer life lure that didn’t require constant refilling and was easily deployed at scale in the field.
Outcome: Testing of these lures in areas outside of the eradication area where we knew there were still rats almost proved too successful. We had a couple of instances of rats chewing out the small holes to make them bigger and gain access to more peanut butter. A useful tool to test for proof freedom as part of a broader detection plan but not in areas with higher rat densities.

The Miramar Peninsula community is special

In just four years, Predator Free Miramar has grown from being a handful of keen backyard trappers to a united community of thousands who are hugely motivated to drive the last rats from the peninsula and make it a haven for native birds.

Predator Free Wellington works side by side with the community and there’s a real sense of pride among Miramartians about the local birdlife, beaches, bush and backyards – and all of the people working together to protect them.

We talked to a couple of Predator Free Miramar’s trappers to understand why they trap, and why they keep coming back week after week…

Predator Free Miramar trappers learning from PF Wellington’s Reino Grundling. Image credit: Dan Henry

Keen to get involved?

We are very close to nailing the last few rats on Miramar Peninsula. They’ve proved tough adversaries, but we have a motivated team and community who are not giving up any time soon. Once we’ve caught the last few rats, the price we’ll pay for being Predator Free is eternal vigilance – which means we’ll need to be constantly monitoring for reinvasion. We have to be ready to pounce at the first sign of any rat incursion.

Other ways people can help are by planting bird-friendly habitats in their backyards and by changing those old habits of throwing out bread for the birds. That bread just attracts rats and mice, so we all need to adjust our behaviour. And finally, this is not just about Miramar, but our neighbouring suburbs too. The more trapping we can get happening across the wider Wellington city, the harder it’ll be for rats to reinvade Miramar! So tell your friends!

The second phase of our eradication project involves 19 suburbs - covering the area from Kilbirnie around the south coast to Ōwhiro Bay and up through Newtown to the CBD and Wellington Harbour. It is an area that is almost twice the size of our Miramar Peninsula eradication and is home to approximately 60,000 people.

Our first challenge before we can start installing the devices on the ground is gaining permission from approximately 7,500 households to have a trap/bait station in their backyard.

On the Miramar Peninsula it took six months of face to face door knocking to get the 3,000 households we needed signed up. Unfortunately with covid impacting all of our lives, we’ve had to pivot our sign up approach and rely on online methods to support the face to face communication.

This is working, albeit a bit slower - at the time of writing this report we have 2,807 households signed up, with 4,693 to go.

We are grateful for the trust the community has had in our team. We could only launch the online campaign because residents know the eradication works and it is safe for their pets and their children.

We are also incredibly grateful for the eight volunteer trapping groups in this phase two area that together have already caught more than 20,000 pests and have a network of over 3,000 traps in backyards and reserves. Thanks to their incredible efforts we already have a community that know the benefits of predator free mahi and we can work side-by-side to ensure this project is a success.

In April, we ran our first ever #ChewCardTuesday campaign, made possible thanks to sponsorship from NZ Post to courier out 2,500 free chew cards. The reports that came back from this campaign have helped us understand potential rat hotspots in phase 2, and which areas we may need to target first.

We are feeling excited and optimistic about phase 2 - there will be some interesting challenges, including the Wellington Zoo, Government House and Wellington Regional Hospital. We’ve also added possums to the phase 2 eradication mix.

Keen to get involved?

The enthusiasm to be involved has blown us away. We’re a third of the way through our target already, and now our three community outreach officers are taking a suburb by suburb approach for gaining sign ups through door knocking, starting with Hataitai and Roseneath, and then moving along to Lyall Bay, Melrose and Kilbirnie. If you haven’t signed up your house yet, please sign up online www.pfw.org.nz/island-bay-to-cbd.

I love the massive increase I’ve seen in all our native birds over the last 10 years we’ve lived in our house - kākā, kererū, tūī, pīwakawaka and kōtare. We go to sleep every night hearing the calls of the ruru and the kākā and it’s one of the best things about living in Wellington.

Sarah, Mornington