Fire ants are forming rafts to survive and travel on flood waters in south-east Queensland, with experts warning the wild weather may accelerate the spread of one of the world’s most invasive species.
After storms ravaged the region over Christmas and new year, Reece Pianta of the Invasive Species Council urged the community to be extra vigilant since red imported fire ants (Rifa) were filmed rafting on flood waters.
“Fire ants are more active before or after rainfall and can form large floating rafts which move with water currents to establish footholds in new areas,” he said.
“We have recently seen evidence of this rafting behaviour on cane farms south of Brisbane.”
He told Guardian Australia a farmer in the northern Gold Coast sent him a video of the rare rafting behaviour. It was the first time Pianta had seen footage of the unusual adaptive behaviour in Australia.
Fire ants will only make rafts when they reach a certain density, he said, with the new footage pointing to a surge in Rifa numbers.
“They are just very effective at spreading, they can feed on anything and they can really dominate a habitat once they move into a new area,” he said.
“The concern we have is that if Rifa are floating on flood waters to lower-lying areas. They don’t just inundate farmlands but wetlands and coastal habitats.
“They are particularly adapted to attacking ground nesting birds and their eggs.”
The ants can kill people and livestock as well as damage infrastructure and ecosystems and have infested about 700,000 hectares in the Brisbane area.
The ants were in November discovered to have broken containment lines when six nests were found 13km south of the New South Wales border in Murwillumbah. Another nest was identified in mid-December on the Queensland-NSW border at Currumbin Valley.
Pianta said the rafting behaviour underlined the importance of properly funding the ants’ eradication.
Rifa are native to South America and are believed to have arrived via infected materials on ships at the port of Brisbane in 2001 but may have been present in the country since 1992. They are dark reddish-brown with darker abdomens. Their nests look like small mounds of loose, crumbly dirt.
“Red imported fire ants are a terrible invasive pest, which cause serious social, economic and environmental harm,” the NSW agriculture minister, Tara Moriarty, said in November.
Recent figures released by the state government show there have been 283 inspections by staff and detector dog teams since the Murwillumbah detection and more than 1,200 drop-ins to the NSW government’s fire ant information bus. All reports of suspected fire ants were deemed negative.
Rifa usually spread because humans move contaminated soil and materials. The NSW outbreak, which has been chemically eradicated, was genetically linked to the ongoing outbreak in Queensland.
An emergency biosecurity order covering the infected Murwillumbah zone strictly limits movements of farming and agricultural materials. Breaching the order can lead to a $1.1m fine for individuals or $2.2m for businesses.
Pianta said members of the public should report any suspected sightings of Rifa or Rifa nests to Queensland or NSW hotlines.
“Let’s all be vigilant, let’s see if we can find them,” he said.
