Archives For rats

Last month, resident Dave Sutherland launched his suburb’s attack on pests in Porirua’s Titahi Bay.

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During the winter months, DOC Ranger Joe Waikari, goes around the East Coast region talking to schools, kohanga, early childhood centres and marae about the need to protect native wildlife from predators.

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Today’s photo is of a mōhua/yellowhead, a small insectivorous bird endemic to the South Island of New Zealand.

Once abundant in the South Island the population declined dramatically with the introduction of rats and stoats. Today they have vanished from nearly 75% of their former range.

mohua

Recent pest control targeting rats and stoats has helped to protect mōhua in 10,000 hectares of beech forest in the Catlins. Results shows that mōhua have increased to the highest level recorded since the population suffered a big decline about 14 years ago.

Rat and stoat levels will be monitored closely with the predicted large beech mast this autumn to determine whether a pest control response is needed later this year as part of DOC’s Battle for our Birds programme.

Photo by Leon Berard | CC BY 2.0.

Battle for our Birds - Beech mast 2014Recently we posted about the problem of increased predator numbers this year, due to predicted heavy beech forest seedfall. We also discussed what this could mean for our endangered native wildlife.

Today, we’re going to have a closer look at what we’re going to do about it…

How does DOC plan to protect at risk populations?

DOC routinely uses traps and other ground based techniques such as bait stations to control rats, stoats and possums. Traps and bait stations will continue to play a significant role in protecting threatened populations such as whio/blue duck in Tongariro, mōhua in the Eglinton valley and kiwi in the West Coast.

Whio. Photo: Matt Binns | CC BY 2.0

Our whio are nationally vulnerable, with less than 3,000 remaining

However research has shown that rapidly rising rat numbers produced by mast conditions can overwhelm trap networks. Ground based control on its own does not protect threatened bird and bat populations from these predator explosions.

The study of pest control techniques during two localised rat plagues in 2006 and 2009 through DOC’s Operation Ark multi-species protection programme showed that aerial 1080 treatment knocked down rat plagues to near zero levels where ground based methods were not effective on their own.

DOC is prepared to significantly expand its aerial 1080 operations in South Island beech forests in 2014/15 to respond to rising predator numbers.

Beech forest. Photo: Shannan Mortimer (CC BY-NC-SA 2.0).

South Island beech forest

How effective is 1080 in countering these predator threats?

Permanently eliminating rats and stoats is not currently feasible but research during past mast events has shown aerial 1080 to be the most cost effective tool for quickly knocking down predators over large areas and in difficult terrain.

Aerial 1080 has been shown to suppress rodent plagues to near zero density levels for up to five months. Tracking results indicated it can also kill more than 95% of stoats through secondary poisoning.

For example, aerial 1080 used in the Dart Valley in Fiordland during the rat plague in 2006 resulted in 80% of mōhua surviving whereas in uncontrolled areas only 10% survived.

At Ōkārito on the West Coast aerial 1080 timed to target rats after a beech mast in 2011 doubled the nesting success of kea. Kea pairs in the treated area produced about four chicks each whereas those in the untreated area produced only one due to stoats and possums preying on nests.

Young kea. Photo: Brent Barrett | CC BY-NC-ND 2.0

Aerial 1080 timed to target rats after a beech mast in 2011 doubled the nesting success of kea

As well as being fast and effective over wide areas, aerial 1080 operations cost approximately a third the cost of most ground based alternatives.

Get more information about the use of 1080 for pest control.

How much land managed by DOC is currently treated with aerial 1080?

Pest control cycles vary but over the past five years DOC has treated an average of about 140,000 hectares with aerial 1080 specifically to protect forest ecosystems and native species. This represents about 2% of the 8.7 million hectares of public conservation land which is managed by DOC.

TBfree New Zealand also carries out aerial 1080 operations over an approximate 300,000 additional hectares of public conservation land to protect dairy herds from possums infected with bovine tuberculosis.

Together these combined aerial 1080 programmes cover about 440,000 hectares or approximately about 5% of all public conservation land managed by DOC.

Giant snails/Powelliphanta. Photo: Kathryn and Stefan Marks | CC BY-NC-ND 2.0.

The Battle for our Birds doesn’t stop at protecting our birds, but other species such as our giant snails/Powelliphanta, which are among our most threatened invertebrates

How much more land is DOC preparing to treat with aerial 1080 as part of its Battle for our Birds beech mast response?

The exact scale of DOC’s aerial 1080 programme in the coming year will depend on whether predator populations reach levels which trigger a response but, if required, DOC is ready to increase its aerial 1080 protection in the South Island by about 500,000 hectares.

This together with TBfree New Zealand’s planned programme would result in a total of about a million hectares of public conservation land being treated with aerial 1080 in 2014/15 – about 12% of the land managed by DOC.

To increase its on-going protection for native species DOC is also committed to increasing its aerial 1080 programme by about 50,000 hectares a year for five years. This means DOC itself will be supporting the 2014 beech mast response by routinely treating about 400,000 hectares of public conservation with 1080 by 2019.

What is this expanded programme expected to cost and how will DOC pay for it?

This new Battle for our Birds programme is expected to cost about $21 million over five years. It is a priority project for DOC and will be funded out of the Department’s existing budget using efficiencies gained from improved pest control techniques and co-ordination of operations.

The heaviest beech forest seedfall in more than a decade is predicted this year. It is expected the increased seedfall will lead to an explosion in the numbers of rats, mice and stoats, who will turn to our native birds for food once the seeds disappear.

Predator plague cycle

Beech trees generally seed every four to five years but weather conditions over the last two summers—a cool summer followed by a warm one—appear to have triggered a bumper seed or “beech mast” event. Intense and widespread flowering was witnessed throughout North and South Island beech forests during spring and early summer, prompting the need for urgent action.

Past experience has shown that when a beech mast occurs, it leads to a dramatic rise in mice and rat populations, who feast on the plentiful seed all winter. To give you an idea of how quickly they can multiply, a single female rat can potentially produce 10 offspring every eight weeks—that’s a lot of rats!

An explosion in rodent numbers leads to a sharp rise in the number of stoats, which also pose a lethal threat to many species.

Rat eating Fantail chicks at nest. Photo © David Mudge. DOC use only.

Rat eating fantail chicks at nest

In spring, when the seed runs out, germinates and rots, these predators will then prey on native birds and their eggs, as well as other critically endangered critters such as native bats and snails.

This will put some of our most threatened species at risk of extinction including:

mōhua/yellowhead
kākāriki karaka/orange-fronted parakeet
pekapeka/short-tailed bat
whio/blue duck
Powelliphanta snails

Kea and tākahe are also at risk of being preyed on by stoats.

Yellowhead/mōhua. Photo © Michael Eckstaedt. www.naturephoto.co.nz. DOC use only.

Yellowhead/mōhua

Landcare Research estimates that 25 million native birds die through predation every year in New Zealand and the beech mast is expected to make the situation much worse. For example, there are only 200–400 wild orange-fronted parakeet left and during the beech mast that occurred in 2000, 85% of the southern population was wiped out due to the rat plague.

85% of the southern population of orange-fronted parakeets were wiped out

85% of the southern population of orange-fronted parakeets were wiped out during the beech mast that occurred in 2000

DOC staff will monitor the amount of seed produced this summer and seedfall in the autumn. Rat tracking will also take place in February and May.

DOC scientist Graeme Elliott says, “So far we’ve only been able to get a visual idea of the issue. We’ve seen lots of flowering during the spring, which caused huge clouds of pollen above the forests.

“The seeds are developing at the moment but in February we’ll be able to start counting them to get a better idea of the scale of the mast. We do this by shooting down branches at the top of the tree, where they’re exposed to the sun and produce the most seeds.

“The best indicator will be the rat tracking. If the numbers dramatically increase or are already high in February, we’ll know we’ve got a big problem to deal with.”

Last night the Minster of Conservation, Dr Nick Smith, announced DOC’s plans to respond and launched our largest-ever species protection programme called ‘Battle for our Birds’. We’ll talk about this in more detail over the coming weeks. For now, you can learn more about it on the DOC website: www.doc.govt.nz/battleforourbirds.

10 year old Jamie Hamilton is a Year 6 student at Glenorchy School, she often goes out trapping with her dad, a DOC trapping volunteer. She writes about a recent trip to Lake Sylvan.

At different times of the year my dad and I go trapping at Lake Sylvan.

Jamie heading out to check the traps

Jamie heading out to check the traps

The reason we go is so that DOC can monitor how many stoats and rats there are and to save our native birds. My dad and I do 34 traps and if you walk a little further past this trap line you will end up at the Rockburn Hut.

At the start of the walk there is a little sign and it shows all the markers that are shown on the track. The two that that we look for are the orange and blue markers, the orange are track markers and the blue ones show where the traps are.

Jamie with her dad.

Jamie with her dad

Sometimes dad and I have to leave really early so we can get back at a reasonable time. Once me and dad left at 8:00 am and got back at 5:30 pm. On that trip we got four stoats and one rat. One of the stoats was a baby and one was a white one, there wasn’t much left of them though. The white stoat is a normal stoat but its coat colour just changes white in the winter.

On the track we often see robins and rifleman and hear the beautiful song that the birds make.

A robin sitting on a trap at Lake Sylvan.

A robin sitting on a trap

I love checking the trap lines for DOC, I know I am helping to protect our native birds and I get to spend a day with my dad doing something we both enjoy.

Jamie sitting on rocks by Lake Sylvan.

Jamie sitting on rocks by Lake Sylvan

By Jane Dobson, Wellington-Hawkes Bay Conservancy

Fresh to the Wellington-Hawkes Bay Conservancy, I heard about the Oroua Blue Duck Protection Project in the Ruahines and an inspired volunteer team led by Janet Wilson. Needing to know more I contacted Janet and invited myself along on the January trap line check and rebait.

Oroua volunteers getting ready to head off.

Oroua volunteers with coordinator extraordinaire Janet Wilson: Jen James, Janet, myself, Henry Milne and Thierry Stokkermans

Janet arranged to meet us all at the Oroua River car park with equipment, advice and a refresh on DOC 200 traps. As beacons, maps, eggs and rabbit bait were split between packs, Janet told us about the previous weeks training where a man ‘just blanked’ and let his free hand slip and set off a trap. “That’s never happened before, he was lucky to get away with grazed knuckles. “Have fun and look after each other up there,” Janet looked at me. Apparently matching people with similar fitness levels is one of her many challenges.

Jen the Crossfit trainer, Henry the anaesthetist, and team leader/ mechanical engineer Thierry set off with me in tow. We planned to get to Iron Gate, split into teams to reach the Ngamoku Ridge tops and Triangle Hut, return to Iron Gate, then walk out the river line on Sunday. I reassured myself that I was fitter than I looked – for ‘a lady from the Wellington office.’ They’d been warned.

Olearia colensoi, leatherwood, below the Ngamoko tops

Olearia colensoi, leatherwood, below the Ngamoko tops.

Jen and I headed up the ridge. The thought of an evening swim in the Oroua’s emerald pools propelled us from trap to trap. Before long we had an efficient leapfrog system. The beech trees, lime green crown ferns, glorious leatherwood and tussock covered tops made up for any squeamish moments with the stoat and rat carcasses. I even imagined rabbit ‘jerkey’ could be tempting if you were in a tight spot.

Thierry and Henry walked upriver spotting several trout AND a whio/blue duck perched on top of a DOC 200 trap in the river, with three young ducks nearby. Was this cheeky whio mocking the stoats from its macabre pedestal, or alerting Henry and Thierry to the missing trap.

The girls didn’t see any whio but were rewarded nonetheless with Guiness at dinner (fantastic leadership Thierry) and choice bombs on Sunday. The low river, blue sky and cool and clear  river made for a stunning walk out.

Total count: 13 stoats, 13 rats. 

January 2013, Team Oroua in action.

January 2013, Team Oroua in action

Meanwhile, Janet spent her Sunday checking the self-resetting traps up the Tunupo Stream, a tributary of the Oroua. In May 2012 volunteers helped install 37 of these new A24 traps made by NZ company Good Nature. They were bought with funding from the He Tini Trust and Horizons Regional Council. These traps don’t need to be checked as regularly as DOC 200’s, but need re-gassing every six months or so. A down side is there is no clear pest count – the dead critter tends to breakdown or disappear from under the trap.

Jen James baiting for high-altitude stoats.

Jen James baiting for high-altitude stoats

Due to Janet’s nightly phone calls, training trips, constant advocacy and more, the project’s volunteer base is ‘committed and developing.’ Enthusiastic people are needed to prevent the situation the Manawatu Deerstalkers found themselves facing in 2011 with the same few people doing all the work. The coordination takes ‘AGES,’ Janet told me. ‘The Palmerston North tramping club is a great help, Manawatu Deerstalkers still help, the DOC newsletter Keep Tracking On advertises for volunteers. I also put notices in the huts with tear off numbers. We’ve got a committed but developing volunteer base. I’m investing in the training weekends, hoping it will pay off.’

Whio enjoying the view from a washed out trap.

Whio enjoying the view from a washed out trap

Janet won the 2012 Individual Manawatū Rangitīkei area Conservation Award, which recognised her on-going commitment to protecting wildlife through stoat control in the Te Potae o Awarua project, the Manawatu Gorge, and for rescuing the Oroua Blue Duck Protection Project from folding in 2011.

You’re an inspiration Janet Wilson – volunteer coordinator extraordinaire.

Click here to find out how to get involved.

Evidence of an ‘A24’ trap kill up Tunupo Stream.

Evidence of an ‘A24’ trap kill up Tunupo Stream