Chemical camouflage

Messing with the minds of predators like ferrets, feral cats and hedgehogs is showing promising results for New Zealand’s birdlife.

In New Zealand, controlling predators is a critical part of preserving our native biodiversity. Ferrets, hedgehogs and (to some extent) cats rely mostly on smell to hunt. For their experiment Grant Norbury and his team smeared Vaseline infused with bird odour (chicken, quail or gull) onto stones at around 700 randomised points across two 900-hectare sites in the braided riverbeds of the Mackenzie Basin.

‘Chemical camouflage is a concept of trying to mess with predators’ minds,’ Norbury said. ‘When predators hunt, they cue into signals that represent food. So the idea is to provide signals to them that don’t have rewards.’

It was the first time the theory had been tested on such a large scale, and success will be measured by the survival of braided river birds like the banded dotterel and the nationally vulnerable wrybill.

‘We measure egg survival because that’s the easiest thing to measure, and so far we’re getting quite encouraging results. We’re finding significantly higher nesting success on the treatment sites compared to untreated sites. To really confirm it, we want to swap the treatments in the coming nesting season. If we reverse the treatments and get the same results that would be very compelling.’