Mammalian predators rely primarily on smell as their main cue, enabling them to detect food from a distance. Smell is usually a reliable strategy for food location.
As part of long-running research into the behaviour of introduced mammalian predators in New Zealand and Australia, researchers from Manaaki Whenua – Landcare Research and the University of Sydney asked whether it might be possible to manipulate predator behaviour by using misinformation. Could we use unrewarded prey odour cues to fool predators, and make them ignore real prey cues? If we could make predators less efficient at hunting, might we also make them miss real prey?
Over two nesting seasons, the researchers tested the response of cats, ferrets and hedgehogs to false odour cues at nesting sites for three shorebird species – the banded dotterel, wrybill and South Island pied oystercatcher. These native bird species nest on the ground on braided rivers in Canterbury and are highly vulnerable to predators. The researchers made odorous pastes from bird carcasses and feathers – and tested whether repeated exposure to these odours would affect the predators’ behaviours.
They set out the pastes at 300 to 400 points across nesting sites before the birds arrived to nest, and also during the nesting season. Predators’ behaviour was then compared to that at testing sites without paste.
Camera traps were used to monitor predators’ interest in the paste, and to monitor the survival of nests with and without odour paste.
In the second nesting season, the paste/ no-paste sites were swapped to increase the reliability of the results. All three types of predator were attracted by the paste odours, but ferrets and cats, in particular, quickly lost interest when there were no prey associated with the scent cues.
Thus, when the birds arrived to nest, the predators had already altered their behaviour by ignoring bird odour, including that of the real birds.
The effects on nest survival were striking for all three bird species: compared with non-treated sites, odour treatments resulted in a 1.7-fold increase in chick production over 25 to 35 days and doubled or tripled the odds of successful hatching.
For banded dotterel, the researchers estimate that this intervention could result in a 127 per cent increase in the population size in 25 years of annual odour treatment.
The method is best suited to small areas of vulnerable biodiversity where lethal control methods are difficult to implement.
Lead researcher Dr Grant Norbury of Manaaki Whenua – Landcare Research worked with colleagues at the University of Sydney, Dr Catherine Price and Prof Peter Banks, who developed the idea.
Dr Norbury says that this field experiment provides clear evidence of altering predators’ perceptions of prey availability on a landscape scale, and “could significantly reduce predation rates and produce population-level benefits for vulnerable prey species at ecologically relevant scales, without any direct interference with animals”.
Photos: Grant Norbury
An ambitious predator control programme in and around the Aorangi Forest in the southern Wairarapa is delivering some impressive results.
The Aorangi Restoration Trust is working in partnership with TBfree NZ, which has carried out three aerial applications of 1080 aimed at controlling possums and rats, covering 33,000 hectares. The first 1080 drop was in 2014, with subsequent drops in 2017 and 2020. The trust, which was established in 2011, is encircling the drop zones with predator control measures to help reduce re-infestation and the flow of predators from the forest into surrounding land, including the coastal penguin zone.
Trap lines cover more than 140 kilometres, with traps placed every 100 to 200 metres up most of the major streams in the forest.
"Much of the land is in private ownership and we are very fortunate to have the support of local landowners. They and many other volunteers, both local and regional, help check and service the traps," the trust says.
Recently, trustee Joe Hansen, with Sandra Burles and Nigel Boniface, walked the true left of the Opouawe River from the sea to the Kaiwaka bridge to mark out trap sites at an average of 150 metres between sites.
"We marked 37 trap sites on the true left and also saw four dotterels en route,"
As well as predator control, the trust and its partners carry out monitoring, penguin recovery and education activities.
Victoria University has been tasked with monitoring the impacts of 1080 in the Aorangi Forest and part of this work is assessing birdsong before and after the 1080 drops. Research so far has shown that 1080 has not reduced the numbers
of native birds.
It involves monitoring six sites in the Aorangi Forest Park and two in the Rimutaka Range ,which are used as reference sites. Chew cards, tracking tunnels and wax tags are used to monitor pest abundance.
Bird recorders and observations are used to monitor native birds, while pitfall traps and weta hotels are used to monitor invertebrates.
Monitoring in 2016 also found an unclassified species of forest gecko.
The main areas of research, including that carried out by summer research students are:
▪ Changes in abundance and recovery of pest species
▪ The impacts of 1080 on native bird species.
▪ Does the forest go silent after a 1080 drop?
▪ The impacts of 1080 on invertebrates, with special emphasis on weta populations.
Bob Burgess, project manager for the trust, is a retired scientist. He trained in plant ecology and recently worked at Victoria University.
He continues to work closely with the university’s scientists.
He says they are already getting some interesting results. A frequent claim of aerial 1080 opponents is that “the forest goes silent after a 1080 drop”.
“The birdsong actually got louder immediately after the first drop – across all native species,” Bob says.
That finding was from 3000 hours of acoustic recordings, made at various times of day and night, by 24 automated sound recording devices which were on location for several months before and after the 1080 drop.
Other Victoria University research projects have looked at the relationships between the forest, seed masting and the effectiveness of 1080 in reducing rat numbers. “Rat numbers went down immediately,” says Bob, “but the rats were back to pre-1080 levels within six months. Possums too recovered, but at
a much slower rate. It took about two years for possum numbers to get back to pre-1080 levels.”
The scientific research has practical implications for pest control in the park.
“Pest control needs to be responsive, triggered by the results of monitoring pest and bird numbers.
And timing of 1080 drops,” says Bob, “needs to be in early spring, so there
will be low rat levels when the birds are breeding.”
Birds will then have a rat-reduced ‘window of opportunity’ in the critical period when eggs, nestlings and incubating adults are vulnerable to predation.
Ducks Unlimited Director Jim Law is one of the trustees of the Aorangi Restoration Trust, along with Clive Paton (chair), Anne Firmin, Chris Lester, John Bissell, Mark St Clair, Tony Didsbury, and Joe Hansen.
Predator control goes on hold
The Department of Conservation had to suspend all non-essential services,
including predator control programmes,during Covid-19 Level 4, which began
on March 5.
But the timing of the lockdown in many ways couldn't have been better, Brent Beaven, Predator Free 2050 manager for DOC, said.
Most birds weren't breeding, and most of the pests weren't breeding either, so he didn't expect to see a massive rise in pest numbers.
Predator control activities on public land were able to resume from May 13 when New Zealand moved to Level 2.
There was more good news the next day, with Predator Free 2050 receiving an
extra $76 million ($19 million a year) in the 2020 Budget, enabling it to co-fund new predator free projects around the country.
Thousands of hunters, however, had to wait until May 23, when the delayed duck hunting season began. It was extended until July 12.
In many places, wildlife appeared to enjoy the break from the madding crowds.
In Dunedin, the Otago Museum's Tropical Forest, home to hundreds of tropical butteries, staff reported some unusual cheeping sounds.
They discovered the forest’s zebra finches, apparently for the first time,
were raising chicks, partly because of the break from the usual stream of human visitors.
In Australia, scientists took advantage of the lack of maritime activity to learn the language of the Burrunan dolphins, a rare species which live in the Gippsland Lakes in Victoria. The scientists set up acoustic sound monitoring and, for the first time, were able to listen to what the dolphins had to say.
Further afield, there were reports of wildlife occupying abandoned spaces. These included a herd of wild goats taking over a town in north Wales, pink flamingos flourished in Albania, and wild boars roamed the streets of Haifa, Israel.
DU Director Dan Steele looks at another tool to help in the fight against predators.
The biggest problem with conservation in New Zealand is complacency and believing that someone else is looking after mother nature on your behalf.
So many people leave things to the Department of Conservation and believe that that’s enough.
It’s not, it’s going to take a huge combined effort from many New Zealanders and particularly landowners to slow the decline in our biodiversity caused by these introduced pests.
But it is not easy to start a conservation project, it is usually an extra job for already busy landowners and who pays, how is it going to be maintained and what should be done?
We ran a really good trapping demonstration for our local sustainable farming group last week, the Taumarunui Sustainable Land Management Group.
Mustelid expert Professor Carolyn (Kim) King, of Waikato University, gave a great overview of New Zealand pests, how we got to this point and whether pest-free New Zealand has any hope of success. The jury is still out on this.
But she believes future technology may well make it possible.
We’re trying to demonstrate that it’s quick and easy to set a few traps around the farm; knowing what to do is often the biggest obstacle with farmers. Then of course there is the capital cost to set up traps and the ongoing maintenance. Goodnature, a Wellington pest company founded 13 years ago, is certainly making the setup and the maintenance easy with their well thought-out technology.
The new Chirp feature on their traps provides bluetooth information from the trap direct to your smartphone.
You link your phone to the trap and it logs the GPS coordinates, and when you check the trap, it tells you how many strikes the trap has had and when.
Then once you’re back into cellphone reception or internet connection, the information is automatically uploaded to the cloud onto the Goodnature world map.
Your traps and kills can be viewed by anyone looking at the map – they show up orange.
Cunningly though, when people are viewing your traplines, they can only see to within 150 metres of where you have your traps placed, so people can’t turn up and steal or sabotage your traps. The owner of the traps can however have their GPS coordinates down to a metre or two.
We are finding the A24 Goodnature traps a good way for people to sponsor some traps, to be involved and stay in touch with how the conservation work
It’s so important to be holding our ground against predators; this week at Blue Duck Station, we have had a kaka sighting and a report of a bittern booming.
The Goodnature A24 rat and stoat trap automatically kills 24 rats or stoats (and mice) one after the other, before you need to replace the CO2 gas canister. When the pest tries to reach the lure inside the trap, they brush past a trigger which fires a piston, killing them instantly. The piston retracts and resets ready for the next pest. The trap comes with a pump that refreshes the lure automatically for six months. Three different trap kits are available: a trap-only kit, a trap with a counter or a trap with Chirp.
Ian Jensen writes about the ‘necessity of continuance’ in the war against pests.
For several years, no records were kept to show the numbers of predators dispatched on the property, though one Tims trap early on accounted for about 35 ferrets over three years.
In February 2008 a comprehensive record was started, compiled mainly from pests that my dogs found, hares that keen hunters dispatched, along with wasp nests that have been eliminated as well as bait stations for rats and mice.
In 2009, with assistance from Greater Wellington Regional Council, a number of DOC 200 traps were provided, and others have been purchased since.
The property is coastal dunes south of Te Horo, with about 10 hectares of wetland, where there are nine traps located on the wetland margins. Weasels are the predominant catch, followed by stoats, rats and ferrets and a few small to medium rabbits.
It seems bird numbers, particularly pheasants, have increased over recent years along with Californian quail. With the ducks, it is harder to make a comparison as water levels also play a very important part in the survival of the young and moulting birds.
For my traps I use the juice from ‘Sardines in spring water’; I have a small sealed container kept in the fridge that I store it in – once every three months seems to be enough to keep up the interest.
Some say it is not counting the numbers caught that matter, but it is the numbers still around that matter. However counting the numbers caught keeps one well motivated to continue the onslaught.
In 2017 there were 29 weasels and four stoat caught, while in 2018 that dropped significantly to four weasels, three stoats and a ferret.This year has spiked with 21 weasels, 16 stoats and two ferrets – we also passed the 500 mark with hedgehogs since records began.
Blue Duck Station, where DU director Dan Steele and his family live, work, conserve and save ducks, have discovered traps that seem to be super efficient. Here is something about them.
We are pretty excited about the latest technology for dealing with pests; Good Nature’s A24. The A24 is quite different from the DOC200 (350 of which we maintain), and has some advantages over it. The A24 does not need regular maintenance as it automatically re-sets and is therefore great for places with difficult access. The auto- resetting also means they have the potential to catch more as there is no waiting period between kills.
For these reasons we plan to put them in the far back blocks and inaccessible ridges on the station. We have also purchased some counters to indicate when to replace the gas canisters and to give us some catch numbers.
The A24 cannot tell you what it has caught as the carcasses of the creatures rot away or are often carried off by other predators so we will continue to rely on our DoC200s for this. We plan to record A24 catch numbers however and add them to our catch database, linked to our GoogleEarth application.
We believe that anything is worth giving a go in our battle against predators and protecting our whio and other species. We do not plan to replace our DoC200s with A24s but will use them as an addition and in different areas. We are looking forward to seeing results after we have had the traps up for a while.
It is also worth mentioning that the public feel the same, as two of our A24s have been sponsored by visitors as part of our ‘sponsor a trap’ programme!
*Blue Duck Station hosts a number of overseas people they call eco warriors, who visit and work on the station, learning about conservation and helping to protect the Whio.
Animal pests and predators are a major threat to the survival of New Zealand’s special native flora and fauna.
A wide range of techniques and tools are used to control pests, depending on the threats and the terrain. Ground control is Department of Conservation’s main approach. They use traps, bait stations or culling. It can prove highly effective where the terrain is suitable and regular checks can be made.
It is DoC’s most widely used pest control approach with more than 400,000 hectares under ground control management. Around 80 percent of the Animal Health Board’s operations are ground control. Ground control methods are precise, but are also labour- intensive and expensive.
This website will inform you of three new types of humane kill traps developed by the Department of Conservation and Philip Waddington. These traps are designed to assist conservationists with their protection of native species that have almost been wiped out by introduced predators.
These traps are regarded as innovative and responsible:
The DOC 150 and 200 humanely kill three pest predators - stoats, rats and hedgehogs.
The DOC 250 targets and humanely kills four pest predators - ferrets, stoats, rats and hedgehogs.
DU member of Pohangina wetlands Gordon Pilone, sent in these shots of a recent catch.
He uses DOC 250 traps to eliminate stoats, rats and hedge hogs.
The kill traps are elevated on a plank on blocks to delay weed invasion and stoats seem to like “running the plank”.
Gordon said a hen egg as bait can be successful even at several weeks old. Also used successfully for stoat kill, is a Timms tunnel trap baited with a fish head.
To help protect the birds, a trapping programme is underway to get rid of ferrets and other pests to provide a safer environment for rare native birds in the Wairarapa Moana wetlands.
These include Australasian bittern, royal spoonbill and the dabchick. Greater Wellington Regional Council (GWRC) started trapping around Matthews lagoon and Boggy Pond in July. Using covered traps that exclude birds, pest animal officer Steve Playle was successful straight away, catching 13 ferrets and three feral cats in the first month.
“These are large and powerful predators that need to catch and kill regularly. If we can control them around the wetlands, the wetland birds are bound to increase in numbers,” he said.
Hawke’s Bay wetland bird expert and Ducks Unlimited president John Cheyne, said numbers of Australasian bittern were low in a count taken earlier this year, and the work being done by officers like Steve should help raise bird numbers in the wetlands.
“There is a lot of great wetland habitat at Wairarapa Moana, but I only heard eight bitterns calling. There should be more.
Trapping ferrets and feral cats should allow them and all the other ground-nesting birds to breed more successfully.” The trapping programme is part of a wider project to enhance the wetlands around Wairarapa Moana, involving the councils, DoC, iwi, farmers, environmental groups and the community.
Story courtesy of the Greater Wellington Regional Council.
Motu Scenic Reserve is a 20 hectare kahikatea wetland forest located just past Motu township in the Eastern Bay of Plenty.
The reserve is unique as it contains: an oxbow wetland (crescent-shaped lake lying alongside a winding river) and an original kahikatea swamp forest, one of only two percent left in New Zealand.
The remainder of the reserve is alluvial forest with a low canopy of houhere (lacebark) and wheki-ponga (tree fern). Kahikatea (white pine) emerge 30 metres above the canopy. Motu Scenic Reserve is also habitat for aquatic bird species and provides valuable habitat for weka and common bush birds. Visitors can access the reserve, although there are no formal walking tracks.
In 1913 the government approved 70 acres of native bush and lagoon for Motu Scenic Reserve now managed by the Department of Conservation. Visitors from the Motu Hotel often went boating on the lake in the early 1900s when the hotel was at its most popular.
A photo taken by well known local photographer William Crawford in the 1900s features the oxbow lake with Christian Hansen rowing his children and James Whinray (nearby Whinray Scenic Reserve is named after).
DoC undertakes trapping, weed control and restoration planting at the reserve.
The trapping programme targets rats, mustelids and possums. While weed control focuses on Japanese honeysuckle, old man’s beard, English ivy, Japanese walnut and various willow species. Visitors can learn more about problem weeds in the reserve from an information panel installed next to the lake.
Sponsorship from Matua Wines has enabled restoration planting of manuka, flax, karamu, kahikatea and koromiko on the grassy margins of the reserve.
Motu Scenic Reserve is 47km from Opotiki, and 87km from Gisborne, turn off at Matawai on the Motu Road. At the township keep left, cross the bridge over the Motu River and the entrance to the reserve is located on the corner of Motu Road and Phillips Road. Nearby places are the Whinray Scenic Reserve Track and Pakihi Track.For more information check out doc.govt.nz