The poison, known as 1080, is used in New Zealand to eradicate invasive mammals such as possums, rats and stoats, which threaten the country’s native wildlife. Initially developed as an insecticide, 1080 naturally biodegrades in the environment over time and eventually becomes harmless. However, it is highly toxic and has no antidote, and many countries have banned its use.
New Zealand uses 80 to 90% of the world’s 1080, aerially dropping bait laced with the poison. Its use is highly controversial, with critics claiming that it can also kill native species such as birds and frogs.
The Department of Conservation (DOC) plans to use 1080 on Moehau Mountain, on New Zealand’s North Island. However, one of the main concerns about the planned drop is the potential effects it could have on two unique and endangered frog species, Archey’s frog and Hochstetter’s frog.
One of only a few surviving species from an ancient frog family, Archey’s frog is considered a ‘living fossil’, with primitive features such as a lack of eardrums or vocal sacs, and muscles to move a tail despite the frog having no tail to move. Unfortunately, this unusual frog is under threat from predation by non-native mammals and by the deadly amphibian disease chytridiomycosis, and is now considered to be Critically Endangered.
Hochstetter’s frog is also a primitive and unique species, and is found in just ten fragmented and isolated populations. Listed as Vulnerable by the IUCN, it is under threat from chytridiomycosis as well as the destruction of its habitat.
It is not known for certain whether 1080 has any impact on frogs. The DOC says that the poison has been used previously in areas of frog habitat and that rather than harming the frogs, it has benefitted them by removing predatory mammals.
“Last year DOC started a controlled experiment in the Whareorino forest and dropped 1080 in an area where the frogs (Archey’s and Hochstetter’s) had been well monitored and excluded it from another well-monitored area,” said Phil Bishop, a scientist at the University of Otago. “The data has yet to be fully analysed as its still early days and still being collected, but the results are looking good and the frogs seem to be doing as well if not better in the area that received the 1080 drop.”
However, others believe that insects may feed on the poisoned bait, and the frogs may therefore ingest the poison when they eat the insects. There are also fears that 1080 could have less direct impacts, with chronic exposure to the poison potentially making the amphibians more vulnerable to disease or affecting their circulatory or nervous systems. This adds to a growing body of research worldwide showing that the non-lethal effects of pesticides can cause considerable harm to wildlife and humans.
There is also concern that native birds could be affected by 1080, although others point out that this threat is outweighed by the benefits to the birds of removing non-native predators. Local people are also concerned for the safety of livestock and pets, with dogs being particularly vulnerable to the lethal effects of the chemical.
Some opponents argue that safer, less controversial pest control measures could be used, and accuse the government of self-interest as they own the factory which produces the 1080 pellets.
“Invasive pest mammals comprise an obvious threat to New Zealand biodiversity. But to dismiss out of hand suggestions that 1080 might harm native species through sublethal physiological effects and thereby contribute to long-term population declines is just foolish,” said Bruce Waldman, an expert on New Zealand’s frogs. “Until we know why Archey’s frogs are dying… we cannot just proceed on the assumption that dangers that they incur by exposure to 1080 drops have been sufficiently mitigated. To do proper studies on 1080’s effects on frogs would not be difficult, so why have they not been done?”
Despite the controversy, the DOC has stated that the poison bait drop is still to go ahead, with the aim of saving native frogs and birds from invasive predators.
Find out more about amphibian conservation on ARKive.
Liz Shaw, ARKive Text Author