Wellington Scoop

Death by chocolate – trial aims to kill rats without poison

News from GWRC
The Wellington Regional Council and the Wellington City Council are taking the phrase ‘death by chocolate’ to a new level with an innovative rat control method – using chocolate instead of poisonous bait. The councils are partnering to investigate how well rat numbers can be controlled without poison at Te Ahumairangi (formerly Tinakori) Hill.

“As far as we know this area doesn’t have possums so is an ideal trial site to focus on the rodent population,” says Senior Biosecurity Officer Paul Horton.

Greater Wellington’s biosecurity team has set up several self-setting traps made by Kiwi innovators Goodnature. The traps feature chocolate lures that attract rodents with their sweet smell and then instantly kill any curious rodents. The lures are designed to last six months and the trap can kill 24 rodents before CO2 needs to be replaced.

“This is just one method we can use to get our rodent populations under control,” says Paul. “Because the traps can be used more than once before checking it would save staff time spent checking traps regularly. Plus, native birds aren’t drawn to the traps and cannot interact with the bait.”

According to Daniela Biaggio, Urban Ecology Manager for Wellington City Council, “to protect biodiversity in urban environment we need to continuously improve what we do and how we do it. This is a great example of how we embrace new ideas and innovation so we can stay ahead of our biosecurity challenges and have a city thriving with wildlife.”

The rodent numbers on Te Ahumairangi Hill are being monitored by tracking tunnels – cards in tunnels with ink on the floor that show footprints. These are showing numbers remaining at low levels. The site also has chew cards with peanut butter smeared on them. Staff are able to see what kind of pests are visiting by looking at bite marks left in the cards.

Report from RNZ
Wellington’s councils are putting a new twist on the idea of death by chocolate. The regional and city council plan to use chocolate to lure rats into traps that will kill them instantly, to see how well rats can be controlled without poison. The regional council’s biosecurity team has set up several traps on Te Ahumairangi Hill, in the suburb of Northland.

Senior officer Paul Horton says because there are no possums in the area, it’s an ideal site for focusing on rodents.

The chocolate lures can last six months and the trap can kill 24 rodents before CO2 needs to be replaced.

Urban Ecology Manager for Wellington City Council Daniela Biaggio said protecting biodiversity in urban environments needed continuous improvement. “This is a great example of how we embrace new ideas and innovation so we can stay ahead of our biosecurity challenges and have a city thriving with wildlife.”

The rodent numbers on Te Ahumairangi Hill are being monitored by tracking tunnels – cards in tunnels with ink on the floor that show footprints. These are showing numbers remaining at low levels.

The site also has chew cards with peanut butter smeared on them. Bite marks left in the cards allow staff to identify which pests are present.


  1. TracyJane, 18. January 2019, 14:22

    I wish choc worked as well as GN thinks….I tried to catch “something” with GN chocolate lure, then GN stoat lure and then eventually got King Rat with eggs, feathers and a bit of rabbit bait in a big box trap. Suspect it was the egg that worked as he had become addicted to my chook eggs. Local pest control guy reckons the GN possum lure works way better for rats than the chocolate. Having said that, I had got several rats n mice with choc before the smart rat refused….perhaps he’d seen his little ratty friend get it in the neck.

  2. Manny, 19. January 2019, 6:24

    It sounds nicer when we substitute the word “control” for kill, but it is not truthful. You can’t have a urban city thriving with wildlife, as a city is not wildlife’s habitat or environment. We have native birds thriving in some surrounding bush areas within the city, we had this thriving before the predator free program. Lucky for us(?) there are no bigger predators than humans, no others talking like that about their exploits of trapping and killing, none other but us the predators. Humans also are the ones that cut down the native birds’ habitat and created a concrete urban environment but we like to blame rats for the “biodiversity” challenge of an urban city.

  3. Farmer Bill, 19. January 2019, 9:19

    Well said Manny. However towns/cities can be a relative haven for some critters (excepting getting crushed by a car) since the mono-cultural, round-up sprayed, brodifacoum treated, 1080 bombed NZ countryside is not a nice place to live for our bees, insects, birds (native and exotic), hedgehogs and the other small furry mammals that DOC wants to exterminate.

  4. TrevorH, 19. January 2019, 9:44

    Wherever humans store food or discard food waste there will be rats. The “Predator-Free” campaign is a cruel con-job. The biggest threat to our wildlife and the to the health of the planet overall is posed by humans. Mass immigration and mass tourism into New Zealand over the past decade have not only over-burdened our infrastructure and services but also severely compromised our environment. Yet we misguidedly ignore these factors and pursue a hate campaign against quadruped mammals instead. It’s the old scapegoating ritual so common in early religions (see James Frazer’s “The Golden Bough”), and it will prove about as effective.

  5. Andy Mellon, 21. January 2019, 12:43

    And we’ve discussed this before. If Alberta, Canada can keep out rats, regions of New Zealand can do it. And those who say that humans are the greatest issue are trying to evade doing anything at all. Even if there were no humans in New Zealand, many of our native species would become extinct due to the pressure from the remaining invasive species. Those who wish to do nothing are willing to condemn iconic species to the history books. But I do hope better, more effective and more efficient pest control measures become available.

  6. Mel G., 21. January 2019, 15:10

    A bit to late to save the Moa but let’s remember this is one bird the eco-fascists can’t blame on small mammals or the much maligned two-legged Pakeha!

  7. Katy Mansfield, 21. January 2019, 15:17

    Andy – not so fast. Three rats have been found in Alberta in 2018 since the big claim was made about total eradication. And wait for it, one rat was found by another hated creature of DOC and TOP – the domesticated cat!

  8. Barbara Smyth, 21. January 2019, 16:55

    My experience of living in the country on my lifestyle block has been if you plant a range of shrubs and trees you will attract a range of birds. Over 14 years I have helped transform a 20 acre grass field into a mini forest with gum trees, deciduous trees and native conifers such as the Totara.
    The bird life has increased amazingly, both in number and species. We have never needed to poison anything.
    I believe that humans are part of nature and we have the wherewithall to improve things benevolently.

  9. Andy Mellon, 21. January 2019, 17:30

    Did you read the article Katy? The claim isn’t that there are no rats in Alberta, but no breeding rats and those that there are, are caught. In fact, the article I linked says “So we actually get about two rats a month.” For an area the size of Alberta, this is incredible and puts the idea that New Zealand can’t be free of rats totally in the shade. Alberta has 4m people and an area of over 600,000sq km. NZ has a similar population and less than half the area. If New Zealand became ‘rat free’, I’d still expect rat incursions around ports, airports etc. and you’d put a dense ring of trapping around such points of entry. So, I would think even a ‘rat free’ New Zealand would still have more than 3 rats caught in any given month.

    And think Katy, if there were no rats here at all… there’d be no reason to kill them, so you could be happy that none of the furry critters were being tormented at that juncture.

  10. Katy Mansfield, 21. January 2019, 18:25

    Andy except that the kiore rat is regarded as taonga to some but presumably not to you.

  11. Andy Mellon, 21. January 2019, 20:38

    To those for whom the kiore is taonga, the Kaka, Kiwi, Tieke, Hihi, Kokako, Tuatara, Whekau, Huia, Piopio are and were taonga. I guess in this instance it comes down to priorities. I note there weren’t many objections to chasing down a Kiore that was loose on Tiritiri Matangi. Also worth noting that unlike the other species I mentioned above, the Kiore can still be found in the wider Pacific region and is a species of “Least Concern” under the IUCN measurement system.

    If the Kiore was gone from New Zealand, it still survives elsewhere. If any of the species I mentioned are gone from New Zealand – then like the Whekau, Huia and Piopio – they’re gone for good.

    Do you think the Kakapo was worth saving, Katy? Or the Black Robin? Invasive predators had to be cleared from a number of islands for them to survive. Do you think they’d still exist if that work hadn’t happened, or do you think that they just weren’t worth the effort, cost and mammalian corpses?

  12. Andy Foster, 22. January 2019, 7:26

    Thank you Andy – again !
    You are 100% correct – even if every human left New Zealand tomorrow that would not save the remaining indigneous species. In fact most birds and lizards would be killed off by predators. We have put the proverbial fox in the hen house. Doing nothing is not an option if we are to save the 80% of bird species and just about every lizard species, and all frogs, and probably many plant species.
    New Zealand has the highest proportion of endemic species of any country on the planet. As you say – if they are gone here, they are gone everywhere. In my view we need to be kaitiaki – to show stewardship and to actively, and I mean actively look after those precious species. That means predator control.
    Manny – we absolutely can have a city thriving with indigenous wildlife. Wildlife – just like us – needs a home and food (habitat) and security (from being eaten). Bird numbers are clearly increasing significantly across the city. That is a result of protection of land, natural and active revegetation, and pest control. It is the combined work of Councils, community organisations and tens of thousands of individual Wellingtonians. Thank you all !
    Collectively we are making a huge and positive difference. Wellington City has gone from ecological basket case to being a show case in 25 years. Becoming predator free is another major step. It won’t be easy, but it is certainly possible and a huge amount of research and planning and work is going into that goal. It is enormously exciting. 2019 is a big year.

    Cr Andy Foster
    Predator Free Leader, Wellington City Council

  13. Brian B., 22. January 2019, 7:50

    Just a thought Andy but I see the pohutakawa, flax, karaka, cabbage tree, akeake and NZ mudsnail are doing so well overseas that they are getting called ‘invasive pests’. Its a pity some Laughing Owls, Wattle, NZ Thrushes and Moa weren’t exported to environments where could have thrived too.

  14. Andy Foster, 22. January 2019, 9:16

    Brian – maybe. The definition of a pest is something in the wrong place. Ecologically the issue will be what the import displaces.
    The danger of us humans moving everything around so much over the last few hundred years is a bit like mixing all the colours together – you risk lose the uniqueness of anything anywhere.

  15. Brian B., 22. January 2019, 10:12

    So it’s the uniqueness and not the well-being of species that is the issue? I think we must add the ‘well-being’ of the organisations concerned. Alfred Kahn rightly noted that organisations look to their own well-being (read jobs and pay) first. For NZ ecology we can insert WCC, GWRC and DOC and the academic departments of various universities. Killing pests and monitoring ecology keeps people in a job.

  16. Andy Foster, 22. January 2019, 13:01

    Brian – I am sure that everyone involved in those fields would be delighted to no longer have to do that particular job because we have become predator free. A lot of people are working very hard, and I have to say with ever increasing amounts of knowledge to save the many many unique species that inhabited these islands for thousands and in many cases millions of years before we came along. That is a job so worth doing.

  17. Andrew, 22. January 2019, 14:09

    What would be the motivation of the countless volunteers then Brian?

  18. Brian B., 22. January 2019, 16:13

    I’d gladly be informed of their motivation Andrew as clearly the welfare of trapped small mammals must be of scant concern. It’s sad to see children being educated in killing and surely this must harm NZ’s reputation internationally.

  19. Andrew, 22. January 2019, 17:41

    Children being educated in killing is nothing new so why the outrage now? I was, when I went trout fishing with my father and grandfather.

    As far as I know all traps used by volunteers are kill traps, designed to kill quickly. Therefore I’d argue people who help trapping are concerned with the welfare of the small mammals. The volunteers obviously feel strongly enough about things to drop the keyboard and do something.

  20. Barbara S, 22. January 2019, 18:26

    Brian B. I looked at that link about the children learning how to kill possums and it really shocks me to read NZ is going this way. No wonder NZ is becoming a violent place.

  21. Andy Mellon, 22. January 2019, 21:54

    I’m reading a lot of whataboutery and no alternatives being offered. So, I can only assume there’s a number of people here who aren’t worried at all about the survival of iconic native species.

    As a volunteer for supporting native species (though I mainly keep my input to population surveys that both precede and follow 1080 drops), my main motivation is the survival of a unique species that has been said to have the intelligence of a 5-year old child. Given how precarious some of our species are, I’d like to avoid any more outcomes like the Bush Wren, primarily wiped out by an irruption of Black Rats on their last surviving outpost.

    The Orange Fronted Kakariki is teetering on the brink for example. Do you help protect their breeding populations in areas like the Hawdon Valley with trap lines, 1080 drops etc. or are you happy for them to die out. Those are your options. The evolutionary timeframe for slower breeders like parrots won’t help in these circumstances.

    So, what’s your solution – Brian, Katy et. al. I’m guessing from what you’ve posted that you’re happy with the extinction outcome, but I’m surprised that you expect everyone to be happy with that.

  22. Gerald T., 22. January 2019, 22:45

    Andy I think the other contributions are calling for benevolent human intervention. Planting a range of plants etc and working with other countries as opposed to the development of a ‘predator’ list and the 100% extermination of everything on the list with all the ensuing collateral and emotional damage.

  23. Alice W., 23. January 2019, 9:30

    Andy is the NZ Falcon on the predator’s list? It eats small birds and other live prey.

  24. Andy Mellon, 23. January 2019, 9:35

    Well, an evidence based approach to that suggestion would be nice. A prime and expansive remnant of native bush in the Hawdon Valley, Arthur’s Pass National Park isn’t stopping stoats and possums from taking chicks from Kea nests, feral cats from killing female adult Kea on the nest or the local population of Orange Fronted Parakeet from falling.

    In such cases, how is planting more plants or working with other countries going to help?

  25. aom, 23. January 2019, 9:43

    For heaven’s sake Gerald – do you believe for one moment that the extinctionists would accept any control tools as being a suitable ‘benevolent human intervention’? It hasn’t happened so far and no doubt won’t. Next, how much planting would you expect would compensate for the non-use of the endemic species protection methods that are currently being used. The dynamics are simple. Planting a native tree requires propagating and establishing a viable seedling – three plus years. Time and effort is then required to clamber around difficult terrain, especially in Wellington to carry then plant each one. Finally, decades are required for the trees to become established. It takes the ‘treasured possum’ about 30 seconds to demolish it, immediately depriving the endemic species of the means of survival. Would any rational person invest time and effort in such a Quixotic endeavour? As for working with other countries, why would one think this isn’t happening. As for the value of such collaborations, one needs to consider the uniqueness of the flora and fauna that this country inherited prior to the introduction of predators. International omnibus solutions are probably of only limited value.

  26. Mike Mellor, 23. January 2019, 11:45

    Gerald, the only people supporting 100% extermination are those who, in the absence of any viable alternative, oppose 1080. It’s a shame that they don’t seem to understand that that will end up wiping out whole species, while 1080 will help ensure that every species will not be under threat in its natural habitat.

  27. Gerald T., 23. January 2019, 12:01

    Mike Mellor – I’m sure that some of the eco-fascists who want 100% extermination of all small furry mammals in NZ that they classify as ‘predators’ will support the use of 1080 to help achieve their ends.

  28. Mike Mellor, 23. January 2019, 12:47

    Gerald T: nobody is suggesting “extermination” of small furry animals – there will continue to be plenty of them outside NZ.

    But people opposing 1080 are supporting extermination of NZ native wildlife, because that’s what will happen without 1080 (or a viable alternative).

  29. Andy Mellon, 23. January 2019, 13:59

    @Alice W. NZ’s endemic species thrived when birds like the Karearea and Pouakai were the main native predators in the absence of mammalian/ground dwelling predators. There was a balance. Do you have any evidence to suggest that the extinction of any endemic species lost thus far were due to the Karearea? On the other hand, there are plenty of examples of extinctions that can be placed on invasive mammalian species. That balance has become totally skewed as a result of invasive predators.

    Without intervention, a balance will return to our ecosystems and that balance will be without a number of iconic species and will, instead, include large amounts of ground dwelling mammals – much like any other forested country. It really is up to the great masses to decide whether you have any interest in these iconic NZ endemic species surviving. Some of us are trying to help preserve these species using evidence-based methods, but are being labelled (according to this thread at least) as self-interested sociopaths. Quite frankly, if that’s what it takes to save species like the Kea, Kiwi or Tuatara, so be it. But I would be delighted to have realistic, evidence-based alternatives rather than the ‘whatabout humans’ and ‘what about endemic predators’ – which are complete red herrings.

  30. Alice W., 23. January 2019, 14:36

    Thanks Andy for your explanation of what is on the NZ predator list. It’s those ‘predators’ that post-date the arrival of non Maori. So the Australian hawk is safe since it colonised NZ about 800 years ago which is clearly before Europeans.

  31. Andy Foster, 23. January 2019, 23:13

    This ongoing debate is barely comprehensible. The evidence is so crystal clear, tragically repeated over and over again. Most of New Zealand’s indigenous birds and reptiles are simply not capable of surviving with the introduced mammal predators. Predators like karearea hunt by sight – best defence is therefore hiding and camouflage. That is completely useless against mammal predators which hunt by smell. As Andy said above, the ecosystem was in balance. Now it is not, and there is no question that we have to intervene to save the many species that will otherwise become extinct. 80% of New Zealand’s bird species are threatened – many are critically endangered. We don’t have time to waste to save them. That means dramatic reduction in the numbers of predators. If we can eliminate those species in some areas, or ideally in all areas, it saves trapping and poisoning in perpetuity.
    Those opposing pest control have been challenged time and again for alternatives – and time and again have ducked those questions. Effectively doing nothing would mean many more species becoming extinct. Planting more trees is good, but it doesn’t stop stoats or ship rats or possums from climbing them and eating the birds, the chicks, the eggs. I have no idea how ‘working with other countries’ will stop predators in New Zealand.
    Again my thanks to all the people who work so hard, whether in their jobs or as volunteers, to give New Zealand’s native wildlife a chance to survive and thrive.