What makes species tick – Brent Beaven, PF2050

To meet the high bar of Predator Free 2050, there can’t be any laurel-resting. Here’s a run through of some of the exciting things happening in the PF2050 space. This is the fourth blog in this PF2050 series.

By Brent Beaven, Programme Manager Predator Free 2050

The Predator Free vision calls for the complete removal of rats, stoats and possums from Aotearoa. We have to take action, they’re causing serious damage.

It’s no small task: these creatures have evolved masterful survival and breeding strategies, honed by millions of years of evolution. If we’re to eradicate them, we’ll need to find their Achilles Heel — some physiological or behavioural trait we can leverage in our work.

That means understanding intimately the things that make them tick: their metabolisms, their motivations, and their fears.

This year, that understanding took a big leap forward when researchers announced they had mapped the entire genome of the ship rat, one of our most destructive pests.

A genome is an organism’s complete set of DNA, including all its genes. A ship rat has around 25,000 of them and knowing what each one does will help us better understand how ship rats disperse, and to develop species-specific toxins.

The genome of the Norway rat — another important predator in New Zealand — had already been mapped, and in July, Manaaki Whenua Landcare Research scientist Dr Andrew Veale announced that his team has also sequenced the stoat genome. Stoats can be especially difficult to trap, so this intimate knowledge of their physiology will be a huge asset as we continue work on a stoat-specific toxin.

Personality matters

Meanwhile, other teams are focussed on predator personalities.

Presently, pest control typically removes around 95% of a target population, but that’s not enough to achieve the Predator Free goal of eradication. Researchers suspect that the 5% of predators that remain may have an intrinsic distrust or fear of traps and/or poison baits.

A big risk of leaving them behind is that they may pass their wariness on to their progeny, creating more and more ‘shy’ animals. And that five per cent of survivors is very expensive: while ordinary pest suppression costs around $20–$30 a hectare, eradication can be an order of magnitude more expensive.

Manaaki Whenua’s Dr Patrick Garvey has been thinking about what makes a survivor. Things like, might they have predictable behavioural characteristics? If so, how can we manipulate those using innovative cues to overcome their caution?

Garvey identified three such cues: the attractiveness of baits or lures, the ‘fearfulness’ of the trap, and the surrounding environment.

“Manipulating any one of these will increase the likelihood that an animal interacts with a device,” he told the NZ Herald recently.

He suggests switching to lures based on predator scent, rather than food, to attract some wary stoats and weasels, while traps or detection devices might be made less threatening by using more natural-looking materials or setting them below ground.

Holding the line

Eradicating those last few predators from big areas will be challenge enough and that’s just the first part, as preventing them from re-invading is a whole other thing.

Predator-proof fences work, but they’re not practicable, or affordable, to able to be used at the kind of landscape scale that Predator Free requires.

That means using physical features as barriers instead. To date, people have looked to high mountains, or fast-flowing rivers, to turn back predators, but our idea of a barrier is changing all the time.

Wellington’s Miramar peninsula is the site of an intensive urban predator eradication project. Possums have already been removed from the peninsula, and rats are now down to very low numbers. Miramar residents are depending on an entirely artificial barrier to keep them from coming back — Wellington Airport’s main runway.

It turns out that any open ground might provide a suitable deterrent, so that tracts of open farmland are now also being considered as moats to defend cleared areas.

Research will start this year to look at predator eradication on farmland and if the placement of traps and bait stations could detect and remove every predator that reinvades — creating a barrier to movement — or a new type of fence.

One glance at a map of New Zealand shows an abundance of large areas that could be cleared of predators if surrounding farmland was utilised as a barrier.

Trapping too

Virtual boundaries (lines of strategically-laid trapping and surveillance devices) are also holding promise.

Predator control company Zero Invasive Predators (ZIP), assisted by funding from us, NEXT Foundations and Predator Free 2050 Limited, is developing an eradication methodology they’re calling Remove and Protect. 

While the Remove part still relies largely on aerial toxins, the Protect part will keep predators out of cleared areas of tough terrain where fences are out of the question. What’s more, a virtual barrier can be easily shifted as cleared areas expand.

ZIP has been trialling Remove and Protect in 12,000 hectares of Westland tiger country, the rugged Perth Valley.

It’s bounded by turbulent rivers — the Perth to the north and the Whataroa to the south, which rats, stoats and possums are reluctant to cross, but the riverbanks are also lined with sophisticated AI detection devices, automatic lure dispensers and traps, all connected to a low frequency radio network.

All 12,000 hectares, once home to an estimated 15,000 possums, were recently declared possum free after none had shown up on any of 143 lured trail cameras for more than 14,000 detection nights, nor in the 700 traps dotting the valley.

Just the same, re-invasion is, for now, a fact of life — stoats re-appeared in the valley in January after months of absence following a 1080 drop. But low numbers of invaders may not be the threat we once imagined.

The CEO of ZIP, Al Bramley, recently told Radio NZ: “The important thing is detecting intruders quickly, and not allowing large populations to establish.

“For possums and stoats, this might be as long as a year, so there’s no need to panic. Meanwhile, we’re continually snuffing them out at the edges, and maintaining predator freedom at the core.”

As our understanding of animal behaviour — what makes an individual skirt around a trap or decide to strike out across a river — improves, Remove and Protect will get easier with time.

Thanks for reading. The Predator Free movement is really important work and it’s going to take a team effort to make it work.

Ngā mihi

Brent Beaven

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For more about the PF2050 strategy, including a run through of the tools that are going to get us there, visit https://www.doc.govt.nz/moving-towards-pf2050