Get the facts

Responding to common misconceptions about predator control to protect pukunui/Southern New Zealand dotterel on Rakiura

With operations underway to protect pukunui/Southern NZ dotterel from extinction and to trial tools and methods for eradicating introduced predators on Rakiura, there’s a lot of action and discussion happening.  

Unfortunately, we’re seeing some inaccurate information being circulated online. 

In response to the most common misconceptions we’re hearing, we’ve summarised some key facts and the scientific studies to back them up.  

We recognise there’s a lot of information to digest, so we encourage you to get in touch if you have any questions or concerns: pukunui@doc.govt.nz 

 

Fact: Rakiura supports a rich array of native species—but the ecosystem has been significantly affected by the introduction of mammal predators.

Misconception: “Rakiura is pristine and untouched”

Stewart Island/Rakiura supports a remarkable range of native species and habitats—but these ecosystems have been deeply altered since human arrival. Like the rest of Aotearoa, the island evolved without land mammals for over 80 million years, apart from three bat species (one now extinct), resulting in wildlife uniquely vulnerable to introduced predators.

While Rakiura retains more native biodiversity than many parts of New Zealand, this appearance can be misleading. Since the arrival of humans and introduced mammals—such as rats, possums, and feral cats—the island has suffered the same steep biodiversity declines seen elsewhere. Birds like the mohua/yellowhead, bush wren, tīeke/saddleback, snipe, kōkako and kākāpō once thrived here but all are now gone. Fossil evidence shows that millions of kuaka/Whenua Hou diving petrels once bred at Mason Bay, only to be wiped out, likely by rats. These losses also extend to native lizards, invertebrates, and entire forest systems.

The idea of Rakiura as “untouched” reflects a shifting baseline—we celebrate what remains, forgetting what has already been lost.

Rakiura is ecologically important, and still harbours species found in few other places, but it is not untouched. Recognising the island’s altered state is the first step toward protecting and restoring its unique ecosystems. Many species continue to decline—only 105 pukunui/southern New Zealand dotterel remain—and concerted action now will help to reverse a history of loss on Rakiura.

Fact: Native species and ecosystems on Rakiura are well studied and understood.

Misconception: “There is no baseline data on native biodiversity”

Extensive data and studies on Stewart Island’s ecosystem exist, including but not limited to: 

Fact: 1080 helps native wildlife recover. 

Misconception: “1080 causes silent forests” 

When 1080 is used to control introduced predators, the populations of native birds, insects, plants, bats and frogs have a much better chance of survival. 

Decades of research, operations and operations show that aerially-applied 1080 bait is the most effective method for controlling introduced predators such as rats, stoats, and possums over large, remote areas. Long-term studies show that reducing predation pressure leads to clear rebounds in native bird populations and the recovery of forest ecosystems. Far from falling silent, forests typically grow louder and more vibrant after 1080 drops. Monitoring also shows no harmful effects on invertebrate populations. 

Some key findings: 

  • Mohua populations have increased dramatically following aerial 1080 drops (Katzenberger & Ross 2017, Elliott & Kemp 2016). 

  • Kākā breed more successfully and produce more fledglings after predator control (Malham & Elliott 2023). 

  • Kiwi chick survival increases significantly when stoats are suppressed by 1080 (Robertson et al. 2019). 

  • A 10-year study by Te Herenga Waka—Victoria University of Wellington scientists found no significant negative impact of 1080 poison on bird and insect populations in the Wairarapa and instead points to the biodiversity benefits of widespread pest control (Bomans et al. 2021).   

Independent reviews, including from the Parliamentary Commissioner for the Environment, support these findings and confirm that 1080 is a critical conservation tool. 

Fact: Native birds, reptiles, and invertebrates are much less susceptible to 1080 than introduced mammals. 

Misconception: “1080 kills everything that eats it” 

The toxicity of 1080 varies widely between species, which is what makes it an effective tool for targeting introduced mammal predators in New Zealand.

A species’ sensitivity to 1080 is expressed as ‘LD50’, which is the median lethal dose per individual that will kill 50 per cent of a study sample. The numbers below represent milligrams of 1080 per kilogram of the species’ average body weight. 

Species and their known lethal dose of 1080 (LD50 in mg/kg of body weight) 

  Rats = 1.2 

  Possums = 1.2 

  Dogs = 0.07 

  Cats = 0.3 

  Deer = 0.5 

  Weka = 8 

  Reptiles (non-native) = 40-550 

  Tree wētā = 91 

  Human = 2

 (Sources: Eason et al. 2011, EPA 2006)  

Native birds, reptiles, and invertebrates generally have much higher tolerance levels than introduced mammals. Dogs are extremely susceptible, and most other carnivores are highly sensitive to poisoning. Herbivorous mammals are less sensitive, and birds and reptiles less susceptible still (Eason et al. 2011). 

While individual non-target deaths can occur, large-scale monitoring consistently shows either little to no impact at population level for birds, reptiles and invertebrates. 

Monitoring and research shows that predator control using 1080 increases the breeding success and survival rate of many native species.  

Fact: 1080 is a tool uniquely suited for New Zealand’s native environment. 

Misconception: “Other countries have banned 1080” 

1080 is uniquely well-suited to New Zealand’s environment. Unlike most countries, Aotearoa has no native land mammals apart from a few bat species.  

Australia, Canada, India, the United States, Mexico and South Africa have all used 1080. In most countries, 1080 is not banned — it simply isn’t registered because those countries have native mammals that would be at risk. In New Zealand, its use is based on a unique ecological need. In this context, 1080 remains one of the most effective tools available to protect native species from extinction. 

Fact: 1080 breaks down rapidly in water. 

Misconception: “1080 contaminates drinking water” 

As a salt, 1080 is highly soluble in water. As such, streams, rivers and oceans have a powerful dilution effect. It also gets broken down into its constituent compounds—individually harmless—by aquatic microbes. This means 1080 is usually undetectable in water within 24 hours.  

The Ministry of Health’s safe drinking threshold is extremely conservative: 2 parts per billion (ppb). For a 70 kg adult to reach a toxic dose, they would need to drink over 70,000 litres of water contaminated at this level in one sitting—far more than any practical exposure scenario. 

Landcare Research—Manaaki Whenua maintains a database of the results of water samples tested by their toxicology laboratory for 1080 contamination. This database includes results from 4196 water samples taken after aerially applied 1080 between 1990 and 2023. Of the 1785 samples tested that came from human drinking water supplies, 0.22% (4) contained detectable 1080 residues. The residues detected ranged from 0.1-0.2 parts per billion—far below Ministry of Health guidelines.  

Fact: Aquatic species do not accumulate 1080 at levels dangerous to humans or themselves. 

Misconception: “1080 contaminates fish and shellfish” 

Aquatic species do not accumulate 1080 at levels dangerous to humans or themselves. A study on koura/New Zealand freshwater crayfish (Suren & Bonnett 2006) shows rapid elimination of 1080 even under artificial exposure to amounts of bait much higher than is realistic for an aerial operation.  

Based on the levels found in this study; to reach a lethal dose a human weighing 85kg would need to consume 40kg of koura tail meat in one sitting. A similar study on eels (Lyver et al. 2005) found negligible 1080 residue in their tissues.  

Fact: We are working with the wild catch and marine farming industries to protect their interests throughout predator control operations. 

Misconception: “It will harm the fishing and marine farming industries” 

Around 60 aerial 1080 operations were completed across Aotearoa in 2024 alone. These predator control operations often took place near primary industry activities, including dairy, meat, wine, and wild catch fisheries, and have not had negative impacts on those industries elsewhere in the country due to the layers of regulation around delivery. 

On Rakiura, ZIP and DOC are working closely with the wild catch and marine farming industries to ensure their interests are protected. One of the key concerns raised by industry representatives has not been food safety, but market perception. In response, the project is taking proactive steps to avoid any bait entering the sea during operations to protect the critically endangered pukunui/Southern NZ dotterel in 2025. 

To meet this commitment, we are using a ‘safeline’ approach—a technique that ensures bait is sown only within operational boundaries. This approach, including the operational boundaries, has been agreed with industry representatives.  

Protecting the sea and the industries that rely on it is a priority for Predator Free Rakiura. We are committed to working alongside the fishing and marine farming industries throughout planning and delivery of the project. 

The wild catch industry has publicly supported the goals of the project and the engagement process to date. 

Fact: There have been no recorded cases of aerial 1080 operations causing harm to human health. 

Misconception: “Residents risk being exposed through food harvesting” 

1080 does not accumulate in the environment, and studies show that small doses are quickly excreted by the body. Long-term, low-level exposure is not harmful—a cup of black tea naturally contains 1080's active ingredient (fluoroacetate) at about 1.5 times the Ministry of Health's legal limit for 1080 in drinking water (Vartiainen & Kauranen, 1984). 

Based on data collected in Ogilvie et al. (2009), plants are able to take up low levels of 1080 from cereal baits in the environment. However, at the highest measured 1080 concentration found in puha during this study, a 70 kg person would have to eat 9.3 tonnes of affected plant material in one sitting to receive a lethal dose.  

There is a recommended caution period for the harvest of animals for consumption following aerial 1080. This caution period and the associated buffers are based on the known home ranges of each animal—for example, the caution period for deer applies to the treatment area and a 2-kilometre buffer around the treatment area. 

The Pesticide Summaries page on the DOC website shows the treatment areas where these caution periods are active. 

Fact: Predator control supports sustainable mahinga kai on the Tītī Islands. 

Misconception: “It will harm tītī harvest” 

Tītī feed far out to sea, where they dive for fish, squid and krill. Therefore, they are highly unlikely to ingest 1080.  

Many Tītī Islands are predator-free today precisely because toxins were used to eradicate predators. These islands now reap the benefits: healthy harvests, booming seabird populations, and restored mahinga kai. 

Fact: The vision of a predator-free Rakiura has been explored, debated, and refined over many decades. 

Misconception: “Predator Free Rakiura is being rushed” 

The project builds on decades of work by DOC, Ngāi Tahu and members of the Rakiura community, including: 

  • Eradication work on many of Rakiura’s smaller islands including Ulva Island (1996), Codfish Island/Whenua Hou (1998) and Taukihepa/Big South Cape (2006) 

  • Successful predator eradication operations on more than 110 islands across New Zealand 

Predator eradication feasibility studies and other documents include:  

Operational progress towards a Predator Free Rakiura is currently limited to a ~7000-hectare trial within Rakiura National Park (the 40,000-hectare 2025 suppression operation is a separate initiative to save pukunui/Southern NZ dotterel from extinction).  

This trial is designed to build knowledge and inform future decisions. The following steps will be shaped by what we learn and ongoing conversations with the community.