Why targeting pest 'personalities' could boost NZ's predator purge

Even pests have personalities - and tailoring our predator-busting efforts to them could help New Zealand on its way to its bold goal of a mainland wipe-out. Photo / Patrick Garvey

Even pests have personalities – and tailoring our predator-busting efforts to them could help New Zealand reach its bold goal of a mainland wipe-out.

The rats, mice, possums and stoats that infest our wilderness are responsible for the slaughter of some 26 million native birds every year.

Now, a scientist has suggested that, in trying to control them as "average" individuals within pest populations, conservationists are critically neglecting each of their unique behavioural traits, life histories and motivations like hunger and mating.

"Individual differences will influence how an animal responds to the risk of entering a trap, scent cues such as food lures, or indeed any management action," Manaaki Whenua's Dr Patrick Garvey said.

"If we focus on the 'average' pest, we fail to mitigate the damage done by 'rogue' individuals that cause disproportionate impact, and we also fail to target 'recalcitrants' – those individual animals that know to avoid standard control measures."

These were the pests that caused most damage - and which proved particularly expensive to wipe out.

"Examples of these problem individuals in a New Zealand context would be the uncatchable stoat inside a fenced sanctuary, the domestic cat that targets a colony of birds, or the rat that refuses to enter a trap," he said.

"To effectively target these pests, we suggest that we need to diverge from a standard approach."

Two years after a workshop between experts, Garvey and colleagues have published new findings setting out how this fresh thinking might be considered in New Zealand conservation efforts.

Garvey had explored the concepts during his PhD research on how stoats interacted with other predators in the wild.

"When we looked at stoats collectively, their general patterns of behaviour were clear - but as individuals their responses were much more variable," he said.

"From a wildlife management perspective, an individual stoat that avoids risky situations or fails to respond to a sensory cue would be very difficult to remove."

Over recent decades, the fields of animal behaviour and sensory ecology have accumulated a wealth of knowledge on why individuals might respond differently to sensory cues.

"It gradually became clear that the application of fundamental animal behaviour could greatly benefit pest management."

How could that be done, exactly?

The new research suggested that conservation managers had three levers to pull when managing pests - the attractiveness of the bait or lure, the "fearfulness" of the trap, and the background environment.

"Manipulating any one of these will increase the likelihood that an animal interacts with a device," Garvey said.

"For example, using a different lure based on predator scent for pests such stoats, weasels or hedgehogs, making a trap appear 'safe' using natural materials or burrowing underground, or focusing on food lures when food is scarce will help target a greater proportion of the pest population.

"Changing or combining attractant, by using different lures based on different pest motivations will also target more individuals within a pest population.

"Management that incorporates principles of behavioural ecology should test the ability of these ideas to increase effectiveness of their interventions."

Garvey noted that some managers were already "exceptional" at trapping pests, as they understood their natural history and their environment, while varying their bait types and control approaches.

"While we can learn a lot from the knowledge accumulated in animal behavior, we can equally learn from the most successful managers, to benefit pest management in New Zealand or conservation efforts worldwide."