Wildlife

Rakitu cove provides a sheltered and welcoming anchorage

Ratting on Rakitu

Last week I had the pleasure to finally visit an island I had long wanted to survey. My perverse reward was finding not one but two species of rats inhabiting the island. Rakitu lies off the east coast of Aotea (Great Barrier Island) – a remote island off the coast of a remote island. Its inverted shape; a valley in the centre surrounded by towering cliffs and tors, lends it English name of Arid Island. With delays to our expedition I was left wondering if the island ever wanted me to visit, but eventually we arrived and I had the pleasure of meeting the descendants of the previous owners also staying out there.

Rakitu as seen looking eastwards from Aotea
Rakitu as seen looking eastwards from Aotea (Source: NZ Herald)

The 328 hectare island was a major centre of Māori activity, and in colonial times was farmed through its central valley and slopes. In 1993 the island was purchased to be managed by the New Zealand Department of Conservation where today it is an open access scenic reserve. Black rats (Rattus rattus) were long known to be present, and our team wanted to assess their abundance, and their impacts on the abundance of native birds, reptiles and invertebrates.

Rakitu cove provides a sheltered and welcoming anchorage
Rakitu cove provides a sheltered and welcoming anchorage (Source: James Russell)

Using an intensive 25 metre trapping grid in the remaining rich native forest in Bush creek, we studied the rat population. Checking only 37 live traps took the entire day, every day. To our surprise, on the first day, we caught a small number of Pacific rats (Rattus exulans) in the forest. This species would have been introduced during Māori occupation, and so it was a surprise that it had never been recorded when its presence was likely, but the abundance of the much larger black rats masked the presence of Pacific rats (locally known as kiore) for a long time, as known from elsewhere. Indeed, the black rats on Rakitu are among the largest ever recorded in New Zealand, averaging over 200 grams weight, and the most dense, at over 20 per hectare. The Department of Conservation intends to eradicate the rats from the island this winter, which is urgent given the declines in bird species and reptiles we were also observing on the island.

Kereru (native wood pigeons) are one of the few bird species still thriving on Rakitu, due to their large body size
Kereru (native wood pigeons) are one of the few bird species still thriving on Rakitu, due to their large body size (Source: James Russell)

Given the extremely challenging terrain (with locations inaccessible to humans where rats could evade trapping) and size of the island (over 4,000 traps would be required if it was even possible), the only way rat eradication (every last rat removed) can be guaranteed would be by aerial distribution of brodifacoum. Some of the local community on Aotea are fundamentally against poison, which as a principle is laudable (poisoning an environment or species is never good). However, evidence from over 100 rat species eradications on islands around New Zealand for over 50 years shows no long-term effects of one-off brodifacoum use for rat eradications. The evidence does show, however, many, many long-term benefits to the resident native species on all those islands. The dilemma is thus not poison or not poison, but poison or rats?

Pāteke (native brown teal) struggle to breed on Rakitu in the presence of rats, with only one pair present
Pāteke (native brown teal) struggle to breed on Rakitu in the presence of rats, with only one pair present (Source: James Russell)

Read All Posts by James Russell

Conservation biologist Dr. James Russell works throughout the world on remote islands and other sites to provide conservation solutions by applying a combination of scientific methods. Follow James on National Geographic voices for regular updates on his own work or other exciting developments in island conservation.
  • Carole Long

    Surely a project to rid the island of such a large population of rats should be acceptable – the benefits are huge and the island could become a haven for our beleagured bird species, as well as being a better place for everyone to live without rodents to worry about.

  • Tony Storey

    Great photos, was this a voluntary expedition ? You forgot to mention that the descendants of the previous owners are dead against an aerial brodifacoum drop.And they still have 2 houses over there so will be directly affected. Not too mention the craypot fishermen wth pots dotted around the Island.. Will they be informed of the dangers.? At Kaikoura a Rahui of 3 years was placed where they had a spill. What will the recommendation for a Rahui be? After all it is akin to a spill, given the fact that poison will roll into the sea from the steep drop off on the Island.The number of traps you give is totally misleading..and WRONG..Only 650 traps are required. Weve done the numbers with expert trappers. DOC use their default poisoning programme to the detriment of the environment. Poisoning is not environmentalism. Once again great shots but another D.O.C propoganda piece.

    • James Russell

      Hi Tony. This was a voluntary/independent expedition, funded by University of Auckland (although DOC supported logistics i.e. boat and housing). With the confirmation of kiore/Pacific rat on the island by us, it changes the numbers game for ground-based eradication. Whereas 50 m spacing works for ship rats, it needs to be 25 m spacing for kiore/Pacific rat. We have a short report on the expedition I can share with you if you send me an e-mail. I do share DOC’s evaluation of the situation, but I wouldn’t consider what I do propoganda.

      • Tony Storey

        how can you say that this was a voluntary/independent expedition….and then in the same sentence, funded by University of Auckland and supported with transport by boat and housing by D.O.C. This defies logic! Surely a voluntary/independent trip involves doing everything independently. Therefore there are no conflicts of interest. I was assured by experienced trappers and people in the industry that 650 traps would be adequate. Over 4000??? you say..mate , your conflict of interest comes shining through for all to see.

        • James Russell

          Hi Tony. Expeditions like this are expensive (4 people for 10 days and freight/transport/food/accommodation/equipment), and I work for the University of Auckland who paid for this one, and we did not receive any payment from DOC for this expedition.

          You might want to go back to your non-disclosed expert trappers and ask them for an update now knowing Pacific rats are here. This rat species is a lot harder to control and ground-based methods such as self-resetting traps have been shown not to work well for them on Aotea/Great Barrier Island. http://www.windyhillsanctuary.nz/wp-content/uploads/goodnature-trap-project-report-sept-2017.pdf

          • Tony Storey

            Im sure your employers would be happier if the information that you report was reflecting reality rather than your obvious bias toward poisoning. Id expect a more thorough examination of the facts….given that is your job…your paid job. We as volunteers have very little in the way of resources to challenge the current poisoning mindset. We do we know we can trap the Island successfully. We need the will power from D.O.C to do it, and they are obliged to take heed of the fact that over half the adult population on Aotea are opposed to the drop.

          • James Russell

            Hi Tony. My only bias is to see rats eradicated from Rakitu as soon as possible before any more species go extinct on it. I don’t mind what method is used, so long as its been demonstrated to work before and is cost efficient, since the NZ taxpayer is paying for this. The full report of our trip was peer-reviewed and is available on request.

          • Tony Storey

            Peer reviewed doesnt magically make your reporting any more credible..the fact that you suggested over 4000 traps needed makes your reporting invalid..in my opinion. The NZ taxpayer should be getting their money back James. And yes i have the full report thanks.

          • James Russell

            Hi Tony. 1 device per hectare = every 100 m, 4 devices per hectare = 50 m, 16 devices per hectare = 25 m. Rakitu = 328 ha. 16 * 328 = 5248 so you’re right its more like 5,000 to guarantee eradication, assuming a trap could even be placed EVERY 25 metres across the island, which is not possible as anyone who has seen the island would know (e.g. looking at the photo).

          • Tony Storey

            been in the trapping business long? You can lay all the math out you like…have you talked to trapping companies about numbers needed ? I would imagine that in your paid capacity job youd have alot of time to reserch non-toxic humane methods rather than roll out the DOC rhetoric. Sorry i was wrong..not 650 traps needed…660

          • James Russell

            Hi Tony. Yes I’ve been in the rat trapping industry for 15 years. Worked on islands all over the world. I currently head the national science challenge project researching non-toxic humane methods and ethics. http://www.biologicalheritage.nz/programmes/risks/hi-tec-solutions

          • Tony Storey

            Well you should know better then! D.O.C clearly have not consultated with the community over this and they do not have a mandate to carry out the aerial drop. They are required to consult with the community which they clearly have not done. They have little idea of the wildlife over there ( a 4 day visit is hardly gathering good hard science), bird and rat densities were unknown until you were brought into the picture. And some of those stats still are unknown. If you are going to eradicate an Island, there should be vast amounts of current data available. And data gathered from all over the Island not just from areas, close to where humans live.

          • Tony Storey

            You also intimate the terrain is a factor …’Given the extremely challenging terrain (with locations inaccessible to humans where rats could evade trapping…..’ Bizz Bell a known poisoner around the world, has deployed bait stations in similar terrain using ropes. All do-able. Another piece of misinformation to bolster your flagging argument. Also in South Island, DOC have deployed rat traps in very rugged terrain. At Rakitu there are a network of caves..how will brodifacoum be applied in these? You mention ‘one-off’ brodifacoum drops. The reality is..many of the Islands are never one-offs but have to have brodifacoum reapplied. We as a population gather our seafood from these areas and are offended that you visit these shores expounding the virtues of brodifacoum use…when we know it can be done another way without any cost to the environment, our food and inhumanely killing target and non-target species.

          • kayaboosha

            And DOC are going to take 100 weka off the island at some insane cost, but happy to kill everything else on the island, Then bring the 100 weka back again. Sounds intelligent. Not.

            There are cave systems on the island which means eradication is an idiotic idea. Eradication 2050 is impossible stupidity of the highest order.
            The aim should be the same as Kaikoura Island. Continuous trapping to keep density at 5% or less. Eradication is an impossibility as we found out a couple of weeks ago on Tiritiri Matangi.

            Who do you people think you are???? This is our back yard you want to poison. 10% of this crap will finish up in the ocean.

          • kayaboosha

            Eradication is delusional nonsense. Give us the money DOC are spending on removing and returning weka, on helicopters and pilots, on poison, on support crew, on continuing monitoring and chasing down any rats that are missed. We will trap it and do the ongoing checking and rebaiting for the same money. We won’t claim to eradicate the rats. We aren’t prone to making nonsensical claims but we would get the numbers down to a level that would allow native species to thrive. Same as what is happening on Kaikoura Island.

          • Sorry James there’s bias all through the report. A brief visit does not entitle you to jump to the conclusions you have. Every observation has blame-on- rats attached to it. It can no longer be helped all such field trips are looking for things to accuse.
            Your report does however highlight the lack of information that DoC has.
            “Look deep into Nature and you will understand everything better” Einstein.

          • kayaboosha

            Hi
            I am requesting a copy of the report. Email address is tomhunsdale@gmail.com
            I look forward to receiving it.
            Thank you

          • kayaboosha

            Windy Hill is an ongoing experiment. You can’t have been following it closely or are selectively picking your information. They are constantly monitoring the traps on Windy Hill and modifying methods and baits. There is an alternative. Stop cherry picking information to back your argument.
            Just out of curiosity, who commissioned your trip to the island and gave you your brief?

            Secondly, you indicate above that the poison operation is urgent given “declines in bird species and reptiles we were also observing on the island.”

            If it was your first visit to the island how can you make a statement that you observed the decline of species? Do you have a report you can share with us with previous densities of population of native species? Also can you share with us your methodology for calculating that decline? No apologies if I sound skeptical, I have become used to disingenuous statements and “data” used by DOC to support their arguments.
            I look forward to your response.

      • kayaboosha

        The whole idea of eradication is idiotic nonsense as was proven recently on Tiritiri Matangi. The implication is poison is a one off cost. No it isn’t, there would be continuous monitoring so that is more deliberate misinformation from DOC. The Tiri rat hunt took two weeks and how many man hours? And they caught one rat. Is that the only one?
        This island is riddled with caves, there is no way to get all of the rats with a drop. One other point, after they do the drop it means the island will be turned into Alcatraz as that’s the only way to check boats going there.
        Time for NZ to move into the 21st century. Rats can be kept controlled with manual trapping, there are alternatives. Any chance we stop destroying the environmental image of this country with insane policies?
        Most of us support actions to help native species thrive but poison is not the answer.

  • Iain Newton

    This island could have been in the heart of a great marine reserve if it was’nt for some of the locals voiciferous hatred for DOC and any thing it stands for.

    • kayaboosha

      Idiotic response to people who disagree with DOC malpractices. Hatred is not the same as disagreement but it is exactly the sort of language we repeatedly see from DOC, Forest and Bird and the other Luddites who think they can capture the planet in a bottle for all eternity. Do you know what the word evolution actually means?? Incredible nonsense from some apparently educated people. Just proves that a few letters after your name are no measure of intellect.

  • david erickson

    Hi James, I would be interested in seeing the full report on your trip to Rakitu, thanks.

    yoodave@xtra.co.nz

  • So Rakitu has kiore and two sub-species of rat co-existing. This raises a whole lot of new questions. Such as; how does this co-habitation without interbreeding work? How genetically unique are the kiore given that they may have lived on this island for 700 years?
    What part do the weka play in managing rats on this island? Kiore and weka are classed as “native” , aren’t they?
    So to achieve some pure avian state two native species must be eliminated?

    The justification for rat eradication needs to be reviewed and more time spent in studying the existing island ecology.
    Having visited and surveyed the island during my time on the weka recovery group I know there are alternative actions that could be done to enhance the biodiversity of this island without eliminating anything by using poisons or traps.
    NZ desperately needs scientists not caught up in the dogmatism of pfnz.

  • Tony Storey

    ??

    • Tony Storey
    • Andrew Veale

      I spoke to James and the comments section is having issues higher up in the system (not him) with many of the comments (including mine which was in support of the work) being flagged as spam for some reason and being deleted. Hopefully the issue is resolved shortly.

  • James Russell
    • Tony Storey

      simply sharing an article that highlights some of your interests. You have taken this off topic. Very not cool but slightly amusing. You havent answered my question by personal email so ill ask it here..who initiated your trip to Rakitu?

    • Tony Storey

      Kiore has been known by DOC and had been recorded on Rakitu many years ago. Obviously that info was not passed onto you.

  • Tony Storey

    …walking the talk is Dr. james Russell….from the University of Auckland bio “I also have a strong interest in animal ethics and environmental values.”
    Interpretations? Animal ethics… he is prepared to let animals die in pain for days, both target and non target species?. Thats apparently is ethical. Environment. ….Knowingly spreading toxic bait over a wide area with much of it spilling into the ocean is ‘good’ for the environment.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (dbraun@ngs.org)

Social Media