1080 use in NZ – Expert Q&A

The use and safety of 1080 for pest control has re-entered public discussion in recent weeks.

The toxin, used in New Zealand to control possums and rats, has a bad rap among some communities, but scientists still say it’s the best tool against invasive pests.

The SMC gathered asked experts to comment on the use of 1080 in New Zealand and possible alternatives.

Bruce Warburton, Science Team Leader, Wildlife Ecology & Management, Manaaki Whenua Landcare Research, comments:

How is 1080 currently used in New Zealand and how effective is it?

“1080 baits are approved for aerial and ground application in New Zealand. For possum control, the baits that are used are cereal based and contain 0.15% 1080. They are dyed green to alert people that the baits are toxic and as a way of making the baits less attractive to birds. The baits also contain cinnamon flavour which is added to reduce the ability of possums to detect the 1080.

“Baits are usually sown at a rate of 1-2kg per hectare, but occasionally higher or lower sowing rates might be used.  Often a deer repellent might also be applied as a surface coating to minimise the risk of deer by-kill. In recent years bait quality has been improved, and now with prefeeding (i.e. first applying non-toxic bait to encourage possums to eat the bait), aerial 1080 operations can consistently achieve kills in the high 90%.”

How does 1080 compare to other pest control tools like brodifacoum?

“1080 is an acute toxin that differs from brodifacoum, which is generally used as a chronic toxic. An acute toxin kills relatively quickly after the animal eats a lethal dose. In contrast, a chronic toxin needs an animal to eat several baits over time until the level of toxin accumulates to the point it becomes lethal. These chronic toxins are very effective against bait shy animals as they get no signal that the bait is bad and therefore should be avoided. However, because animals need to eat more baits than for acute toxins, applying them aerially is more expensive. Additionally, each toxin has different residue and non-target species risks that must also be taken into account when toxins are being selected.”

How does it break down in the environment, including in water?

“1080 is broken down in the environment by naturally-occurring micro-organisms by cleavage of the fluoride carbon bond. Degradation is affected by various environmental factors. In water, degradation is influenced by temperature and the presence of aquatic plants, and in soils, degradation rates are influenced by soil type and soil moisture. Persistence of 1080 in cereal baits is dependent on rainfall, bait type and size.”

Are there viable alternatives to 1080? If so, are they available now or will they be at some point?

“Currently, there are no cost-effective alternative toxins to 1080 that can be aerially applied (brodifacoum baits can be aerially applied but only in specials circumstances). There are alternative toxins that are registered for ground application (e.g. cyanide), and although some have been tested for aerial delivery none of them have proved to be effective.”

Dr Colin O’Donnell, Principal Science Advisor Ecosystems, Department of Conservation, comments:

What are the benefits or impacts on native species?

“One of the main benefits of using 1080 is to control introduced predators so that populations of forest birds and bats can recover.

“Normally, introduced predators such as rats, possums and mustelids prey on a wide range of threatened species including birds, bats, lizards, invertebrates and even freshwater fish.

“These threatened species are heading towards extinction, often declining at rates of >5% per annum, unless predators are controlled effectively. For example, >50% of breeding female mohua and >80% of breeding female kaka are killed in areas without predator control; only 15% of rock wren nests survive, and annual survival of long-tailed bats is as low as 30% when there is no predator control.

“Such predation rates are unsustainable.

“Effectively controlling predators, using the periodic use of aerial 1080, applied at a landscape scale, has led to reversals in the declines of many threatened species in forests.

“For example, in the Landsborough Valley, numbers of native birds have doubled after 20 years of using 1080. Numbers of mohua have increased on study lines from 14 in the 1990s to >300 today. Steady increases in numbers of tui, bellbird, brown creeper, rifleman grey warbler and kakariki have also increased, whereas the declines in other (e.g. kaka) have been halted.

“In the Eglinton Valley, where aerial 1080 is broadcast over >26,000 hectares, numbers of long-tailed bats and short-tailed bats now have the highest survival rates of bats recorded in the world and nesting success of kakas is now >80%.”

Conflict of interest statement: Dr Colin O’Donnell is an ecologist working for the Department of Conservation in the Terrestrial Ecosystems and Species team, based in Christchurch.

Dr Graeme Elliot, Science Advisor Threats, Threats Management team, Department of Conservation, comments:

How is 1080 currently used in New Zealand and how effective is it?

“1080 is mostly applied from the air in cereal based pellets. It targets rats, mice and possums and secondarily kills stoats when they eat poisoned rodents and possums. There has been a recent shift in 1080 use by the Department of Conservation. Previously it was used to control possums to prevent damage to vegetation, but now it is also used to control rodents and stoats to prevent them preying on native wildlife. OSPRI uses 1080 to control possums in order to eliminate bovine TB from wild possums and thus prevent its spread to cattle.

“1080 is very effective at rat and stoat control. Following most operations rats become undetectable (or nearly so), nearly all stoats are killed and possum kills are high. Because rats, stoats, and possums invariably reinvade treated areas, the poison regimes do not aim to kill every single rat, stoat or possum – they will reinvade anyway so it is not worth the extra cost of killing the last one. Thus 1080 control programmes aim to give native animals a respite from predation which lasts for variable amounts of time. In very large blocks, stoats and possums can remain at very low levels for several years, but in low altitude sites, rats can recover in just a few months.

“In recent years, 1080 has often been used in response to beech masts and in these forests rats and stoats can remain suppressed for the whole 3 or 4 year period between beech masts.

“1080 has so far produced rather variable results when used to kill mice. A large number of mice are invariably killed when 1080 is used, but there are always sufficient mice left to allow rapid recovery. It is possible that higher sowing rates of poison baits and smaller baits might give better mouse kills – this is a work in progress.”

What are the benefits or impacts on native species? 

“In recent years the Department of Conservation has monitored the survivorship and subsequent productivity of a range of forest birds during and after 1080 operations. Species monitored include great-spotted kiwi, North Island brown kiwi, whio, robin, riflemen, mohua, robins, weka, morepork, kaka, kea, fernbird and long and short-tailed bats. For all these species the results have been positive; some individuals of some species are killed by 1080, but the deaths are invariably outweighed by the increased productivity and survivorship following the reduction in rat, stoat and possum abundance.

“For some species – the kiwis, riflemen, mohua, morepork, kaka and long-tailed bats – the results are very straight-forward: no animals are killed by the poison and productivity and survivorship goes up following 1080 use.

“For a few species – weka, kea, robin, fernbird – some animals are killed but the losses are far outweighed by the gains.

“For rock wren, we’re unsure whether birds are killed, but even if they are, the losses are more than outweighed by the gains.

“For whio, we don’t know whether any birds are killed, but they definitely benefit. During a recent operation in Taranaki, whio were found to be eating baits, but none were known to have died, and the whio in question had been hand-raised on pellets – they had effectively been trained to eat them.”

How does 1080 compare to other pest control tools like brodifacoum? How does it break down in the environment, including in water?

“The way in which 1080 and brodifacoum work are quite different, and they are consequently used in different situations. 1080 is an acute poison — a toxic dose rapidly kills an animal, but the poison is metabolised quickly so that a sublethal dose might make an animal sick but it will recover and not eat the poison again.

“In contrast, brodifacoum is slower acting and breaks down slowly. An animal can accumulate a toxic dose gradually without making the connection between the bait and any symptoms. Because of these differences, 1080 has traditionally been regarded as the best poison to use when you want a rapid knockdown, but don’t necessarily need to kill every last animal.

“Biodegradable 1080 is very soluble, so it rapidly disperses and then is broken down by common micro-organisms. To ensure a good uptake of toxic 1080 bait, you have to provide non-toxic pre-feed to train the target pests that the bait is OK. This pre-feeding technique ensures that they don’t cautiously consume a sublethal dose and get put off.

“Brodifacoum doesn’t need to be pre-fed but it is very insoluble and breaks down only slowly so that it accumulates in animals and the environment. It is the poison of choice for island eradications of rodents and has been very successful in establishing pest free offshore islands used as a one-off application. But, the Department of Conservation doesn’t use brodifacoum on the mainland because of the risk of it accumulating.”

Are there viable alternatives to 1080? If so, are they available now or will they be at some point?

“Some of what can be achieved with 1080 can also be achieved with traps. However, to usefully control possums and stoats you only need a trap every 20 ha or so and this can make possum and stoat control with traps a sensible option. To effectively control rats, however, requires 1 trap every hectare which for large areas of pest control this becomes impossible. For example, a 50,000ha rat control operation would require 50,000 traps, 5000km of tracks linking the traps and it would take more than 500 person days to check all the traps. DOC anticipates using 1080 to control rats in approximately 1,000,000ha of native forest in 2019 – that would require 1 million traps and 100,000km of tracks – that’s simply not possible and horrendously expensive.

“There is always some work going on to develop new poisons or new combinations of poisons – but there is a long lead time with new poisons and there is nothing imminent that could replace 1080.

“What might an alternative to 1080 look like? The perfect pest control tool for NZ would need to be applied from the air so that it be used in remote back-country areas. It would need to be more toxic to mammals than birds. It would need to quickly degrade in the environment, so that it was poisonous for only a short period of time. It would need to be humane. 1080 ticks all these boxes. The only possible improvements would be if we had a poison that only killed stoats, cats, weasels, ferrets, and possums, but was non-toxic to dogs and birds – an unlikely combination. A poison that also gently put animals to sleep would also make us feel better.  It seems unlikely that we’ll have a poison that meets these criteria in the near future. 1080 is a very useful poison in the NZ situation and we are continually refining its use, while continually searching for viable alternatives.”

What role does 1080 play in meeting the Predator Free 2050 goal? Will there need to be other toxins or methods to meet this goal? 

“This is an area of debate. Some folk think that it may be possible to use 1080 very intensively in such a way that we completely exterminate rats, stoats and possums and then keep them from reinvading until the neighbouring country is also free of rats, stoats and possums.

This presents two difficult technical problems:

  1. finding a way to use 1080 such that 100% of rats, stoats and possums are killed.
  2. finding ways of keeping them from reinvading and doing this at a very large scale.

“Even if strategies for eradication using 1080 can be developed they will probably only be able to be used on remote farmland and public conservation land. 1080 is unlikely ever to be a tool that can be used in settled areas and other strategies will need to be developed. Many ecologists feel that the predator free goal can only be achieved with new genetic tools, in which case 1080 will only play a minor role meeting the predator free goal.”

Is 1080 useful in combating stoats? What tools can be used against carnivorous predators?

“Yes. Stoats are killed when they eat poisoned rats, stoats and mice and the kill rate of stoats is often very high. In large blocks of 1080 treated forests suppression of stoats following a 1080 operation can last for at least a couple of years. Secondary poisoning may also kill weasels, ferrets and cats, but the efficacy of 1080 at secondarily poisoning these animals has not been measured.

“Another tool currently under development is the poison PAPP. It is particularly toxic to mammals and relatively less toxic to birds. Currently, it can only be applied on the ground and offers little advantage over other carnivore control methods. If it was developed as an aerially applied toxin, it would be much more useful – this is a work in progress.

“Traps can also effectively control carnivorous mammals, but at anything other than small scales, trapping is inefficient.”

Conflict of interest statement: Dr Graeme Elliot is an ecologist working for the Department of Conservation in the Threats Management team, based in Nelson. If you require more detailed information, or references or data to back up this essay, please contact Graeme.

Dr Belinda Cridge, Department of Pharmacology and Toxicology, University of Otago, comments:

What are the persistent concerns people have about 1080? 

“As I understand it, the ongoing concerns are around non-target species toxicity and water contamination. Non-target species toxicity means that species that are not being targeted by the poison drop consume the poison and die. Common concerns centre on deaths concerning other native species, such as birds and fish, and hunted species such as deer and pigs. There is debate about how many of these deaths are directly caused by 1080 exposure as compared to other causes.

“1080 is toxic to all species (as a toxicologist, actually everything is toxic if you are exposed to enough of it so 1080 isn’t novel in this regard). However, birds and reptiles seem to have a degree of tolerance. In contrast, mammals are very susceptible to 1080 toxicity and so in NZ where all mammals, except sea lions and a bat species, are introduced, 1080 is an important pest control tool.

“The other concerns are around 1080 leaching into waterways and causing a range of effects to wildlife and humans. Scientifically, the understanding is that the original 1080 compound is broken down quickly in the environment and that 1080 doesn’t persist in the environment or water like many other toxins. This makes it unlikely that it will accumulate in waterways and cause down-stream poisonings.”

Have there been any new developments in research into its effects over recent years? 

“Scientific work has slowed down on 1080 as most recent research efforts are focussed on finding alternatives. Many people will be aware that New Zealand is fairly unique in its large-scale use of 1080, this is because we are in the privileged position of having few native mammals. Therefore, we are uniquely placed to use 1080 in pest control. Since 2014 only 400 articles on 1080 have been published worldwide in scientific journals, so around 100 per year. Many of these are case studies of poisonings (1080 is used in other countries, just not to the same scale) or studies that are referring to 1080 in comparison to other toxins. We understand the mechanism of toxicity of 1080 fairly well and NZ scientists, in particular, have done a lot of work on the toxicity and environmental fate of this compound over many years.”

Are there any areas of uncertainty that more research would be helpful to resolve? 

“From my own interests, I would like to understand more about how 1080 is detoxified in the body as this may give us clues as to why dogs and kea and have a unique sensitivity to the compound. But, this is because this is my area of expertise. I think overall we actually have a very good handle on what the toxin does and at what doses. Developments in targeted application using GPS have improved the overall safety of the compound as it is much less likely to be found in non-target areas.

“These type of technological advances are much more important for the ongoing use of 1080 and to improve its overall use and safety. With that said, I suspect the public will remain sceptical of 1080 due to its history of use in this country. This creates many issues that are not able to be resolved by scientific evidence alone.”

Conflict of interest statement: I am currently bidding for funding to develop alternatives to 1080 for pest-control in NZ.

Associate Professor James Russell, conservation biologist, University of Auckland, comments:

Toxin baits, like 1080, have played a major role in pest control in New Zealand – what other options are being investigated and how would these work? 

“Pest control to achieve biodiversity outcomes (i.e. restore native species) requires removing pests from the ecosystem. Traditionally, the tools fall into the three classes of traps, toxins and biocontrol, and can be either lethal or non-lethal. Non-lethal tools are typically inefficient: they either can’t scale up, are not cost-effective, or in some cases are even less humane than a quick death. Scientists are always refining all three tools so they are more humane, more pest-specific (i.e. impact fewer non-target species), more efficient (i.e. catch pests faster), and more cost effective. For example, new self-resetting traps have been developed, and sowing rates for 1080 have been reduced by ten-fold.

“When deciding what pest control tool to use managers must optimise efficiency (does it kill enough pests to restore biodiversity), humaneness (does it do so humanely), and cost (is it affordable). Currently, aerially-delivered 1080 is the optimal tool for mammalian predator pest control over most of New Zealand (costing $12 – $16 per hectare, being relatively humane, and achieving conservation goals).

“Looking to the future, scientists such as those working in the Biological Heritage National Science Challenge (funded by MBIE), are investigating all three types of tools. They are developing new lures to make trapping more efficient, new toxins which are more humane and only harm the targeted pest species, and investigating the potential of genetic editing as a form of biocontrol. They are also considering the bioethics of predator control, so that the social, cultural and ethical issues of pest control are incorporated into decision making.

“Gene editing is one of the novel pest control tools with most potential, as it could be a non-lethal tool that allows pest populations to breed themselves humanely to extinction (e.g. offspring are only male). However, such a novel tool would require New Zealanders accepting gene editing, and is yet to be even developed (no work is being done in New Zealand at this time), let alone proven as efficient and cost-effective.”

What kind of timeframe might there be for new pest or predator control tools to be used in New Zealand?

“New Zealand scientists, engineers and innovators are always making incremental improvements in pest control tools to achieve better biodiversity outcomes through more efficient, humane and cost-effective tools. These include modifying existing tools (e.g. aerial 1080 delivery) and inventing new variations of old tools (e.g. self-resetting traps). This work is happening every day and government, private landowners and community groups are already using the improved tools across the country.

“Entirely novel tools, particularly those in the area of biocontrol, require extensive laboratory development, testing and regulatory approval to demonstrate safety and efficacy before being trialled in the field. Gene editing as a pest control tool is likely to be over a decade away from deployment in New Zealand, if it is even proven to be viable. Our wildlife cannot wait until such new tools are developed and approved, and so until then, we must continue to use the most optimal tool we have, which is aerial 1080.”

Conflict of interest statement: Dr Russell is on the science strategy panel advising the crown-entity PF2050 and is Project Leader of the Biological Heritage National Science Challenge project: “High-tech solutions to invasive mammal pests”.

Professor Neil Gemmell, AgResearch Chair in Reproduction and Genomics, University of Otago, comments:

Prof Gemmell’s full comments are available as a blog on Sciblogs.co.nz.

What genetic tools might be useful for future pest or predator control? What kind of timeframe might we expect for these to be in use?

“Pest control with current technologies over significant spatial scales is possible, but it’s time-consuming and expensive. The best tool we currently have for large-scale pest control is 1080 (sodium fluoroacetate). It is aerially deployed, with precision, at the lowest amounts required to keep pest species in check so that our native birds and other species stand some chance of survival, and it rapidly breaks down in the environment. The case of 1080 use is well established and it works – where it is used our native species are recovering, where it is not they die, it really is that simple.

“While 1080 is the best tool we currently have in our ongoing battle with mammalian pests, we are constantly seeking improvements to our pest control toolkit. As a nation, we are currently investigating approaches that are more humane, species-specific, and that provide persistent control across large areas without the ongoing cost of deployment. Among this list of new tools, genetic control technologies are promising approaches that might help us meet that goal.

“The most direct approaches currently being explored are species-specific toxins. Essentially, we look for genetic or biochemical features unique to the species we wish to control so that we might identify toxins that will only work only on that species or its close relatives – think of it as a biochemical Achilles heel. To date, there are promising ‘species-specific’ toxins identified for stoats and rats. However, it will likely take many years before such substances can be proven to be specific and approved for use in our environment.

“If we are serious about Predator Free 2050 and wish genetic technologies to be part of the solution we need to step up the conversations, increase our investment, and start planning out what the workflow for this project would look like over the next decade plus. If we start today we need months to plan, several years in the lab, and years for controlled field trials, before eventual deployment at landscape scales. It will take massive effort and years to achieve eradication of possums, rats and stoats (recent models on some hypothetical, ideal, gene drives suggest 20 years from deployment to eradication). This is the New Zealand version of the Space Race and we need commitment and resource aplenty if we are to achieve it. It can be done, but whether we have the resolve to resource this appropriately and see this through to completion remains uncertain.”

Conflict of interest statement: Prof Gemmell has or is currently being is funded by subcontracts from MBIE and the Biological Heritage National Science Challenge to explore genetic pest control solutions including the Trojan female technique and gene drives.