How do kea see 1080 bait?

Highly intelligent, omnivorous and ready to explore anything novel in their environment, kea pose a unique conservation challenge for predator control programmes. Because they are so curious, they run the risk of becoming by-kill during baiting operations. Mitigating this risk to kea has been the focus of conservation research for a number of years.

In 2018 and 2019, researchers at the University of Auckland and Zero Invasive Predators (ZIP) demonstrated that the bird repellent anthraquinone, when applied to non-toxic cereal ‘aversion baits’, could be used to train kea to avoid baits during subsequent exposures—even when baits did not contain anthraquinone.

Unlike humans, many species of birds, including parrots, are able to perceive colours within the ultraviolet spectrum. Prior to this research, it was unknown whether anthraquinone, which is thought to reflect in the UV spectrum, is visible to kea. For learned aversion to work consistently, aversion baits must be visually identical to toxic baits.

“Birds don’t necessarily see the world as we do,” says former University of Auckland researcher now Landcare scientist Dr Amy Martin.

“While 1080 has benefited kea populations significantly, doubling nest survival in some areas, sometimes individual birds consume toxic bait and it’s useful to have an idea why that might be so we can work out ways to mitigate that risk.”

With help from Callaghan Innovation, UV spectral measurements were made of non-toxic baits containing different chemical components. Some contained the bird repellent anthraquinone, while others contained a UV-reflecting bio-marker called pyranine. The baits were either dyed green or left undyed.

In order to investigate how these different baits might look to kea, researchers constructed a computer visual model based on the eye structure of three other parrot species: budgies, crimson rosellas and Amazon parrots.

Critically, the model suggested that parrots, like kea, could not tell the difference between baits that contained bird repellent and baits that did not, provided both baits were the same colour.

Kea were also very likely to distinguish between bait with and without the pyranine biomarker, and between undyed baits and green baits—but the threshold for their ability to detect this difference was low, suggesting this might only be the case in well-lit environments.

“We are very encouraged by these findings, which support our earlier work that a non-toxic bait containing a bird repellent can be used to train kea to avoid toxic baits, provided the two baits are the same colour,” says ZIP ecologist Maggie Nichols. “This means that we are better prepared to manage risks to kea during predator control operations to protect our environment and native species.”

ZIP implemented a kea risk mitigation strategy as part of its predator removal operation in the Perth Valley (South Westland) in 2019, including the use of aversion bait to train wild kea to avoid toxic bait. The results were encouraging.

“It’s early days,” says ZIP Innovation Director Phil Bell, “but seeing the kea population flourish in the Perth Valley after this predator removal suggests we have taken a step in the right direction.”

The research team also included Associate Professor Anne Gaskett from the University of Auckland’s School of Biological Sciences and the research is published in the New Zealand Journal of Ecology.