A new $7.5 million programme, led by Manaaki Whenua – Landcare Research scientists, aims to overcome what's long been a headache for predator-busting efforts – how to eliminate that final 5 per cent which manage to hang on.
While it cost an estimated $20 to $30 per hectare to take out 95 per cent of pests, raising the rate to 100 per cent could bring the cost up to more than $400 per hectare.
And in other cases, the price was far higher: the operation to make the Hauraki Gulf's Rangitoto and Motutapu islands pest-free a decade ago cost as much as $1200 per hectare.
Yet, if that last pocket wasn't removed, the survivors - left in an area with plentiful resources to help them more easily breed - could quickly begin rebuilding the local population.
This means more money has to be spent on repeatedly controlling them, as happened when the Department of Conservation recently needed to reapply 1080 to areas in the Kahurangi National Park.
The project's leader, Dr Chris Jones, said New Zealand was regarded as a world-leader in controlling and eradicating invasive mammalian predators - and much of that could be put down to the pest-killing devices our scientists had innovated.
"But those devices can only achieve complete eradication if all individuals in the target population interact with them, and we know that some don't," he said.
"We aim to ensure that even the most trap-shy individuals can be caught."
That meant solving some tough problems. For instance, was it possible to reveal whether these pesky stragglers had any predictable behavioural characteristics?
And, if so, could we use these against them?
In a world-first approach, Jones and his team plan to hone in on what makes some pest animals resistant to current control methods, so they can develop new technology to beat them.
Animal personality, he explained, was emerging as one of the most important concepts in behavioural ecology.
"This programme will be the first application of personality in pest animal management," he said.
"We already know that trappability of animals at the population level can vary depending on the time of year because of the relative availability of food or because of behavioural changes associated with breeding, but how does this vary at the individual level to make some individuals avoid entering traps or taking baits?"
Jones said the extent to which a pest responded to a cue, like a trap, was always balanced against the perceived risk, the value of the reward, and, ultimately, the traits of the individual animal.
Their work would develop a range of cues cleverly designed to alter the animal's entire perception of risk and reward.
His team would be aided by Maori knowledge – such as traditional trapping and luring methods that drew on sound lures – along with the latest artificial intelligence approaches.
"Artificial intelligence – especially the use of image recognition to identify pest species - has massive potential to help in targeted pest control," senior researcher Bruce Warburton said.
This technology was smart enough to tell the difference between target and non-target species - dis-arming a trap if needed – and even deploy special sensory lures once a pest had been detected.
And if scientists could succeed at total eradication, that might reduce the need for toxins like 1080 to keep being applied.
"We believe we can reduce the cost of eradication by at least 25 per cent, as fewer control devices would be used, due to increased device encounter rates, and shorter time durations needed, due to increased device interaction rates," Warburton said.
"Our collaboration with Māori and Moriori partners will ensure our research responds to their priorities – a first for predator tools research in New Zealand – and that any approaches that we develop are culturally relevant and appropriate for use on the whenua."
The five-year programme is supported through the Ministry of Business, Innovation and Employment's Endeavour Fund.