How a world-first baiting program could save the seabirds of Browse Island

By Esse Deves

ABC Kimberley

Topic:Conservation

Australian researchers hope baiting thousands of house mice from the air using a drone, will help eradicate the invasive species from a WA island. (Supplied: DBCA)

In short:

Australian researchers are eagerly awaiting the outcome of a "world-first" eradication project aimed at ridding a remote West Australian island of an infestation of mice.

It is hoped eliminating the pests using drone-baiting technology will restore threatened seabird colonies on Browse Island.

What's next?

Research teams are set to return to the island in April to gauge the operation's success.

Australian researchers are hoping drone-baiting technology will bring migratory seabirds "back from the brink", by eradicating thousands of house mice that have plagued a remote island off Western Australia's north since the late 1800s.

Browse Island was once a safe haven for migratory seabirds. (Supplied: DBCA)

More than 700 kilograms of bright green bait pellets were scattered across the 17-hectare Browse Island, 450 kilometres off the coast of Broome, in October last year, using a custom-built "hexacopter" from New Zealand.

The drone drop targeted the invasive south-east Asian house mouse, believed to have been introduced during the island's guano mining days or by foreign fishers.

Hundreds of kilograms of pellets were scattered from the drone. (Supplied: DBCA)

"They [the mice] have really changed the ecosystem of Browse Island," Department of Biodiversity, Conservation and Attractions (DBCA) Kimberley conservation coordinator Bruce Greatwich said.

House mice have infested Browse Island, which has severely impacted seabirds. (Supplied: DBCA)

He said the rodents had preyed on seabird eggs and disturbed their breeding patterns — driving the majority of seabirds away.

"They are literally in plague proportions at times and they're just running around all over the place … just constant interactions with the birds that are trying to roost and breed on the ground."

Critical timing

Mr Greatwich said returning the island to its former "ecological character" was critical.

Bruce Greatwich says the drone drop came at a time when the migratory birds have re-attempted breeding on the island. (Supplied: DBCA)

"Browse makes up a chain of islands across the north-west, which maintains the entire breeding population of our seabirds off Broome," he said.

"Without the birds breeding at Browse, they've had to go elsewhere so Adele Island and Ashmore Reef, for example."

Drones built in New Zealand are being used in a bid to eradicate mice on Browse Island. (Supplied: DBCA)

Over the past seven years, a team of Monash University researchers and DBCA conservationists have tried to work out ways to eradicate the furry predators — for good.

But humid conditions and soaring temperatures, paired with the island's spindly dense vegetation, have made baiting the mice by hand or helicopter unviable.

The invasive pests have overrun the island, since the late 1800s and early 1900s. (Supplied: DBCA)

So the team contracted New Zealand technicians, who built a drone to spread rodent baits across the island.

'World-first' targeting house mice

Monash University professor Rohan Clarke said the drone operation specifically targeting house mice was a world first.

"It's especially ambitious when you think about how remote we are," he said.

Mr Greatwich said the technology allowed for greater precision.

Researchers remained at the island to monitor the mice uptake of rodenticide. (Supplied: DBCA)

"If you have gaps in your baiting application, then you're at risk of failing because you really need to get literally every single individual of the rodent that lives out there," he said.

"We were all blown away to actually see it in action … and see the pellets flying out."

Restoring former glory

In the days and nights after the drone drop, research teams watched to see whether the mice ate the rodenticide, by measuring any nibbled baits.

A second scattering by drone was conducted two weeks later to ensure any surviving pest was eliminated.

Hundreds of kilograms of pellets were scattered from the drone to bait an infestation of house mice on Browse Island. (Supplied: DBCA)

Mr Greatwich said while the team remained optimistic, the full extent of the project's success would not be known until they returned to the island in April.

Researchers set up cameras and monitored the mice in the days after the first drone drop. (Supplied: DBCA)

"That is the dream, that we're going to return Browse back to its former ecological state and its glory of supporting seabirds for the region."

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