I smell a rat!

A clever technique that tricks predators into not trusting their noses to lead them to the next meal could protect vulnerable species in New Zealand and elsewhere.

Associate Professor Peter Banks and Dr Catherine Price from the University of Sydney’s School of Biological Sciences, are part of a trans-Tasman team that has won a grant to protect New Zealand's native wildlife, using the strategy.

In a land naturally devoid of mammalian predators, the introduction of ferrets, hedgehogs, stoats, rats and cats have wrought havoc on New Zealand's birds.

"Many of the birds have evolved behaviours that defend them from native avian predators, which hunt mostly by vision, but not from introduced mammals, which hunt mostly by smell," explained Associate Professor Banks. "This has created a behavioural mismatch between the predators and vulnerable native species, and the results have been devastating."

The aptly named Smart Ideas grant, worth $984,300, builds on Peter and Catherine's previous research in which they successfully 'hid' bird eggs in the NSW bush from hungry rats by peppering the environment with unrewarding but same-smelling odour cues. When the rats went to investigate an eggy smell, they found something inedible and no longer learnt to associate that smell with a tasty treat.

Peter and Catherine have joined forces with Dr Grant Norbury, Dr Andrea Byrom and Professor Roger Pech from Landcare Research New Zealand to apply their deceptive odour strategy to New Zealand's birds.

The idea is to give birds a 'window-of-opportunity' to breed successfully before any re-learning begins. "The technique is well suited to situations where there is a need to protect vulnerable prey during critical time-periods. For instance, birds are particularly vulnerable during nesting or after translocation when they are 'settling in' to a new location."In this new study the team will continue to test the idea that vulnerable birds can be protected by using odours."Predators will investigate the odour but receive no food reward," Peter explained. "After several weeks, predators will lose interest in investigating the odour, and we will have deceived them into thinking that bird odours are no longer a profitable cue for food."

"This form of 'chemical camouflage' is a novel technique for protecting valued fauna from scent-hunting predators, and should be particularly applicable to threats to native species from introduced mammalian predators, a problem faced not just in New Zealand but worldwide."

The highly competitive grant from the New Zealand Ministry of Business, Innovation and Employment will be administered by Landcare Research New Zealand and provides funding for two years.