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Weasel Incursion and Response
ZEALANDIA Ecosanctuary

Weasel Incursion and Response

Frequently Asked Questions

The October 2018 weasel incursion of ZEALANDIA garnered a lot of publicity and many questions. We've compiled answers to some of the most common ones that we received.


A bit of background


It all started on 1st October 2018, when we discovered some weasel tracks in a tracking tunnel at the southern end of the sanctuary during a routine pest audit. Immediately plans were set in motion to catch this most unwanted pest predator.

The very next day we deployed 70 DOC200 traps, followed by another 40 traps later in the week. These traps were put out in the sanctuary but left baited but unset for a week. This was done to let the animals get used to these foreign objects within their environment, and so make it more likely that they would confidently enter the traps when they were finally set.

One week later, on the 9th October, we set the traps. By this time, we had seen the weasel a few times on our motion-activated cameras, so we knew what we were dealing with.



When we did our first round of trap checks on Friday, 12 October, we were delighted to discover that we’d caught the weasel!


What is a Tracking Tunnel?


Tracking tunnels are basically tunnels with ink pads, paper and bait inside. The idea is that animals go for the bait, leaving inky tracks on the paper. By using these we can identify what animals have walked through. There are always interesting stories behind these cards, we regularly see kiwi pukupuku foot prints, giant wētā prints and many others!


What bait did you use? How many traps?


We used rabbit meat and eggs for the bait and have now changed to some longer life baits as we move into this next phase. We put out 110 DOC200 traps, and around 60 Victor traps that were moved around as needed. We didn’t use any poison in this operation. The weasel was found in one of the DOC200 traps.


Weasel caught in ZEALANDIA. Photo credit ZEALANDIA


When is the last time this happened?


The last time we had a mustelid incursion was just over 10 years ago. It was suspected they got in when a tree came over the fence during a storm. We see this as a sign of our success in maintaining ZEALANDIA as a pest free urban ecosanctuary.


Have you found anything wrong with the fence?


There were a couple of small things that we found that needed some further attention, but none of these things were particularly convincing entrance sites! An example is a very fine layer of moss that was on the top hat in some areas. Not enough for unwanted animals to gain purchase, but the kind of thing we need to keep an eye on and stay on top of. One possibility was a known very small hole between the top hat and mesh that was found weeks before the incursion in routine checks and fixed immediately – it wasn’t enough to raise alarm and again is an unlikely entrance site (weasels don’t really like to climb), but nevertheless within the distant realms of possibility. Given the number of checks that we have had so far, we are pretty confident that our fence is holding up well and will continue to do so.


What other ways could it have got in?


The weasel could have got in to ZEALANDIA by several ways. We have over 100,000 visitors per year, so it may have come through a bag that wasn’t checked properly. It could have come through a gate while it was open. It may even have been brought over by one of our birds of prey. Ultimately, we do not think we will ever know for 100% how this animal got in, but we have covered all known bases and ensured our systems are robust.

Hopefully we can go another 10 years or more without another mustelid incursion, but the reality is our boundaries are under constant pressure. This is why our routine pest audit systems are crucial to ensure that we are always checking and so ensuring we do not have a repeat incursion.


The weasel was female – could it have given birth in the sanctuary?


It is quite unlikely. The necropsy (animal autopsy) indicated the female adult weasel was not lactating and had not given birth recently. We think she was a recent entrant, sometime between July and 1 October, when she was detected.

We are very pleased to have now had a Department of Conservation mustelid dog through – Kōwhai – with her handler Richard, and nothing unexpected was found. We will though continue trapping and tracking for a while longer just to be completely sure.  


Kōwhai the mustelid dog checks ZEALANDIA.


What has happened to the weasel?


The weasel was handed over to Massey University’s Wildbase and has undergone a necropsy. Nothing was found inside the stomach – unsurprising given weasels have a very high metabolism, but the necropsy was extremely useful for confirming the reproductive status of the animal.


Have you seen any impact of the weasel incursion?


Happily we have not seen any evidence of damage from the incursion. However, as the sanctuary is 225ha of wild ecosystems, any impacts may not have been immmediately obvious.


What are the next steps?


We are focused on continuing to bait, check and re-bait our traps. Our fence checks and repairs will now continue as per usual, i.e. at least once a week. At the same time, we are on hyper-alert, responding vigorously to even the slightest hint of anything out of the ordinary – with the tracking tunnels, camera traps and traps – just to be sure. The decision on how much longer to continue to the current trapping regime will depend on how the next few weeks go.


Thank you!


The success of our incursion response is the direct result of all the support we have gained from so many conservation partners. Wellington is an amazing place to work in conservation. We received help, advice and resources from Greater Wellington Regional Council, Wellington City Council, the Department of Conservation, Zero Invasive Predators, Orokonui Sanctuary, volunteers and members and so many more. A massive thank you for your ongoing support.

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