With a review into the risks of rodent bait in Australia about to be released, an award-winning initiative is using barn owls as a natural alternative to control rats and mice on farms.
Wildlife organisations have called for a ban on second-generation anticoagulant rodenticides due to concerns that they kill and harm wildlife that eat baits or poisoned rodents.
Each barn owl breeding event takes hundreds of rats off Banyula farm. (Supplied: Wildbnb Wildlife Habitat)
Studies here and overseas show some rats and mice are developing genetic resistance to poisonous baits, reducing their effectiveness while potentially increasing their use.
But a pilot project in the Northern Rivers, New South Wales, is offering farmers hope of significantly reducing rat numbers in macadamia orchards.
Barn owls have suffered from eating rats and mice poisoned with rodenticides. (Supplied: Wildlifebnb Wildlife Habitat)
No quick fix
The Owls Eat Rats initiative has been in the works for a decade, with the pilot project launched at Banyula, a regenerative farm at Clunes, about 30 kilometres from Byron Bay, two years ago.
It involved the installation of hunting roosts and barn owl nesting boxes, addressing Australia’s wildlife accommodation crisis caused by clearing trees with hollows that take up to 150 years to form.
Nest boxes are designed for barn owls. (Supplied: Wildbnb Wildlife Habitat)
Founder Alastair Duncan said it took time and effort to establish barn owl colonies, but the impact on rodent control had been so promising that three neighbouring farms had signed up.
“They [owls] move in, they breed and they hunt and each breeding event takes about 1,000 rats out of the system,” Mr Duncan said.
Taronga Zoo senior keeper Megan Geddes and Alastair Duncan celebrate the Hatch award. (Supplied: Taronga Zoo)
“Farmers don’t necessarily want to use poison; it’s just that they don’t have alternatives.
“So when they see something that’s working, they jump on board pretty quick.”
Banyula farm is balancing agriculture with habitat restoration. (Supplied: Bunyula Farm)
Talons instead of toxins
At Banyula, 70 nest boxes — including 12 for owls — span across the property, which has 7,500 macadamia trees and 75 hectares of new plantings of koala habitat and rainforest.
Success is monitored by tracking nut damage in the orchards using trail cameras, physically inspecting nest boxes, and examining owl pellets — the regurgitated fur, bones, and feathers the birds cannot digest.
Rats chew through macadamia shells to steal the nuts inside. (Supplied: Alastair Duncan)
“We’re finding that 90 per cent [of pellets] is rats and the rest is house mice, which are a really significant pest in the agriculture industry,” Mr Duncan said.
Wildlife Health Australia notes increasing reports of toxicities associated with rodenticide exposure in Australian wildlife, including birds, mammals, reptiles and amphibians, and further work is needed to better understand and manage the risks.
Cameras are used to look inside the nest boxes. (Supplied: Wildbnb Wildlife Habitat)
Mr Duncan said secondary rodenticides build up in predators’ bodies every time they eat a poisoned rodent, affecting their hunting, breeding and survival.
As opposed to the days it can take for rodents to bleed to death internally after consuming bait, barn owls are fast and efficient killers.
Banyula director Matthew Bleakley said owls had allowed them to reduce rodenticide use, target applications and choose less harmful baits.
“To be able to one day get to [be] fully rodenticide free would be amazing,”
he said.
Matthew Bleakley says rodenticide use has declined. (Supplied: Banyula)
Conservation zoo provides funding
Late last month, Owls Eat Rats was awarded $50,000 by Taronga Zoo’s Hatch accelerator program, which helps ecopreneurs tackle serious environmental and conservation challenges.
Mr Duncan said the grant would help fund academic research and further his goal of mainstreaming nature-based pest control.
Mr Duncan planned to replicate the project on the Sunshine Coast, where he lives, and was working with the Australian Macadamia Society.
“It’s a massive boost for us,” he said.
“We plan on using it to expand into new territories and generate the evidence that will give the farmers the confidence that we can offer a cheaper and cleaner alternative to poisons.”
’10 to 15 rats a night’
Wildbnb Wildlife Habitat director David Brook spent a decade perfecting barn owl nesting boxes, prioritising comfort and safety.
David Brook says years of work have been spent perfecting the barn owl boxes. (Supplied: David Brook)
Each pair of owls needs at least three nesting boxes over a small area to provide variety in their habitat.
“We realised that the owls were not only breeding back-to-back — so we had four different clutches of owlets in a 12-month period — but they were bringing in 10 to 15 rats a night to feed the owlets,” Mr Brook said.
“The next stage of this project is to rigorously investigate the idea.
“We’re bringing in university and industry partners and looking at just how replicable it is across other landscapes and other industries,” Mr Brook said.
The barn owl babies grow quickly on a rodent diet. (Supplied: Wildbnb Wildlife Habitat)
Mr Brook said wildlife rodenticide poisoning and potentially associated road traffic strikes required more examination.
“We’re now starting to work with the local wildlife hospitals and with Taronga Zoo and universities to better evaluate the impact of toxic rodenticides on the barn owls,” he said.
A dead barn owl found at Port Fairy. (Supplied: Chelsea Fox)
National review of secondary rodenticides
Agricultural chemicals are regulated by the Australian Pesticides and Veterinary Medicines Authority (APVMA).
The APVMA is reviewing anticoagulant rodenticides warfarin, coumatetralyl, diphacinone, brodifacoum, bromadiolone, difenacoum, difethialone and flocoumafen, based on public health, worker safety and environmental safety.
In a statement, an APVMA spokesperson said it was “preparing the documents for our proposed regulatory decision for the anticoagulant rodenticides review”.
“We expect to publish this in the near future, which will start a three-month public consultation period,” the spokesperson said.
