Trappings of success

by Rebecca Priestley / 04 February, 2016
Scientists are literally taking the piss in an attempt to develop a super lure for animal pests.
Photo/Getty Images
Photo/Getty Images

The first time I visited the lab of organic chemist Rob Keyzers, it smelt like cat’s pee. But no cats were in residence: Keyzers was analysing a range of sauvignon blancs to determine what gives some wines the so-called “cat’s pee” smell and others the more desirable gooseberry and passionfruit aromas.

These days, it really is urine you can smell in his lab. As part of a search for an effective super lure for mammalian pests, Keyzers has been analysing the excretion products of mice, rats, possums and stoats. In a project led by Keyzers and behavioural ecologist Wayne Linklater and funded by the Ministry of Business, Innovation and Employment, a team of Victoria University scientists are working to develop a super lure that will be more effective than food bait in attracting pests to traps that can kill them.

Current pest eradication methods include 1080-laced bait drops, single-kill traps and self-resetting traps, which all lure pest animals using food.

“But food-based lures don’t work particularly well when there’s lots of other food in the environment,” Linklater points out. Food-based lures also decay quickly, have to be frequently replaced and are not very effective when animal densities are low, as there’s little competition for food. “Food-based lures aren’t very good at eradicating. You can depress densities down to almost zero, but re-invasion and recruitment within the remaining population mean we need to continually apply them.”

The super lure project aims to eliminate the possibility of pest re-invasion. “We need a lure that’s so attractive we get the last one,” he says.

The alternative to food baits are chemical attractants that mimic the pheromones animals use to communicate with each other. Pheromone attractants are already widely used in traps for insects, which use very simple chemical communication systems.

Keyzers and Linklater’s first challenge is to identify a chemical that will consistently attract animals to a trap. Mammalian communication systems are complicated, involving hierarchical and sexual signalling.

“With a complex mammal, you’ve got a very complicated but subtle interplay of signalling molecules involving a suite of chemicals, all at subtle concentration differences. The level of complexity of these prey-prey, predator-prey interactions – who’s eavesdropping on who, who’s observing signals and making informed decisions based on those signals – is phenomenal,” says Keyzers.

Using a gas chromatograph mass spectrometer, Keyzers has been going through the time-consuming process of breaking pest species’ excretion products into their constituent compounds. He says one sample of rat urine might yield 200 different chemicals, any one of which might be a suitable target for attracting rats from a distance. Each target is then tested in the lab before being tried in the field with traps.

The second challenge – once a suitable attractant has been identified – is to develop it into a patentable commercial product with support from Viclink, the university’s commercialisation office. This could involve combining the attractant – which may itself not be patentable – with other compounds. “That then becomes a patentable product because it’s now a novel formulation and our intellectual property,” says Keyzers.

After more than three years of work, the team have identified four potential rat lures, as well as 11 potential possum lures, which they are now preparing for field testing.

An effective super lure would reduce the trap density necessary for large scale predator control programmes by drawing animals from further away and increasing animals’ interaction rates with few traps. This would get us one step closer to a pest-free New Zealand and help boost our market share in the international pest eradication business.

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