It’s been a few months since our last biosecurity update, and before lockdown hit we were over 80% of the way through ‘baiting the other way around’ as well as trialling an alternative bait DoubleTap in a quarter of our bait stations.

We haven’t let lockdown slow us down at the Ark – we’ve been hard at work behind the scenes to secure an exemption to get back out trapping and monitoring kōkako, as these at-risk taonga are in need of protection as they begin nesting. Our amazing trapping volunteers have been carefully getting back to their traplines, clearing storm debris, replacing traps taken by raging rivers, and taking out pests before they can do more damage to our ngahere.

Every rat caught means more native seeds able to thrive and replace fallen trees, and every possum, rat, and mustelid caught means our manu and their nests are safer. With kōkako already nesting at the Ark and tūturiwhatu/dotterels nesting at Te Henga beach, it’s a great time of year to visit your backyard traps and bait stations!

If you’re in our buffer zone, visit the Ark website to learn more about how we can support your backyard biodiversity. For those further afield, this amazing resource shares conservation tips able to be used in every backyard. Get trapping and weeding now to control pest animals and plants before they’re able to eat our native species, to reproduce & feed their own pesty offspring.

Deer diary

Deer are part of the growing ungulate problem across Aotearoa, with 7 deer species established in the wild here. Forest & Bird has created a series of maps from official data, showing close to 100% of native habitat has at least one species of deer, pig or goat on it, and that the area has increased by a third in the last 8 years.

With recent sightings in the Waitākere Ranges neighbourhood, Auckland Council and DOC are working together and have contractors on the ground responding to sightings. Here at the Ark, we’re relying on our neighbours to keep sharing sightings as soon as they happen to help the contractors stop deer joining pigs at the Ark. While thinking about a deer’s diet might first conjure images of them munching on tasty native plants, they can also devastate nests of ground nesting birds, and have been caught on camera eating the eggs of critically endangered NZ dotterels that nest on the Tin Range of Rakiura (Stewart Island).

You can help by reporting Waitākere deer sightings on the Pest Free Waitākere Ranges Alliance website, which is shared straight to the contractors on the ground.

Trap catch update

Lockdown interruptions have resulted in some interesting trapping results – on the surface it looks like October has been a truly frightening Halloween month in 2021 compared to trapping results from October last year!

Looking more closely, the Spring heat maps below show that while this October saw a lot of pests being cleared from traps, the Spring total so far is almost exactly the same as last year.

It’s likely many pests recorded in October were caught in September, and left waiting for the Alert Level to drop so our trappers could get out to clear and re-set their traps (not a job for the squeamish!). Another spot-the-difference: thanks to a family effort by Ark volunteers/neighbours, since last Spring a new southern trapline was installed at the Ark.

The Spring totals for 2020 and 2021 are made up by similar types of pests too:

  • 64 rats in each spring
  • 7 possums last spring versus 1 so far in 2021
  • 7 mustelids (6 stoats & 1 weasel) last year compared to 8 this spring (7 stoats & 1 weasel)

The winter stats are pretty similar as well: 168 pests caught in June-August in 2020, compared to 142 this year.

The impacts of pests at the Ark last year included the loss of at least 5 of the kōkako nests monitored last summer, so it’s vital that we keep trapping at the Ark and in our own backyards across Aotearoa. With the typical home territory of adult mustelids covering kilometres, and even larger areas when their populations are at lower densities thanks to our trapping, the more backyard traps to catch pests the more backyard birdsong we’ll have. Living only 2.5km from the Ark office, Sam’s dream is to hear kōkako from her Swanson backyard – not so far-fetched with constant sightings in Scenic Drive backyards including this video taken at the end of October of a kōkako on its way from the Waitākere Dam to Spragg Bush!

Backyard trapping with Ark’s trapmaster Ken

Ark trapmaster and Volunteer Representative Ken has been busy with backyard trapping this lockdown. We’d heard from a few trappers across Aotearoa that the standard black plastic traps (centre photo) didn’t quite have the spring power to take out bigger rats. This is troubling for animal welfare, as well as being an issue in pest-free areas such as within fenced sanctuaries. Once a pest has had a negative interaction with a trap (like getting whacked non-lethally), that pest is unlikely to ever go near similar traps again. Trap-shy pests are bad news in pest-free areas that aim to remove every last individual. 

With some tinkering to combine the springs from two traps, the new more powerful traps did the job much more reliably in their homemade icecream container housing. They’re shown in the second photo below, with the store-bought trap on the left, and upgraded double-spring trap on the right. A great solution for better trapping, and re-using plastic waste for safe trap housing with an easy to remove lid!

Ferret lures and field findings

In 2015 a study took place at the Ark to test a new pheromone lure. This was made possible thanks to our amazing trappers volunteering to add the lure to DOC200 traps alongside regular bait.

The researcher was PhD student Patrick Garvey who is now based at Manaaki Whenua Landcare Research. Read some of his research here.

The two-month trial at the Ark (Aug & Sept 2015) monitored capture rates of stoats and rats. In total, one stoat was caught in standard traps and four in lured traps; an increase of 300%, but capture rates were too low to be conclusive. There were 19 rats caught in both lured and un-lured traps (i.e., no difference).

Since 2015, lure trials have been completed at other sites, including the Hunua kōkako recovery project and the Oroua blue duck project. Over 65,000+ trap nights, stoat and weasel captures increased by 150%. This demonstrated that the ferret lure is very effective, but also that capture rates vary among sites (+66% to +300% across Aotearoa).

Another stage of this research is about to start to test the latest developments. The proposed trial will test the natural lure (first trial) and a synthetic version on the same trap lines as the original study at the Ark, as well as extra traplines depending on how many trappers sign up. This will be for a longer period (four months), with more frequent lures changes, and it provides an opportunity to test whether more stoats could be captured without greatly changing the current trapping effort. The natural lure provides a baseline to test the new synthetic lure. Successful testing of the synthetic lure would allow cheap lures to be supplied at landscape scales across Aotearoa.

Ark in the Park is located in the Waitākere Ranges, which are currently closed to minimise the spread of kauri dieback disease.