Cane toad catchers trap thousands of metamorphs in effort to stop southern spread
Thousands of juvenile cane toads are being bagged by conservationists battling to stop the pests spreading beyond their southernmost infestations.
About 10,000 metamorphs (the toads in their post-tadpole stage) were collected last weekend in the Clarence Valley region of northern New South Wales.
While rogue cane toads have been discovered in locations such as Sydney and Melbourne, their distribution is officially regarded as an arc extending from north Western Australia to the Clarence Valley town of Yamba.
Clarence Valley Conservation in Action (CVCIA) Landcare spokesman Scott Lenton said recent dry and warm weather had allowed undetected populations to spawn and propagate, resulting in mass hatchings in areas including Micalo Island and Maclean.
“The southern frontline has been at this location for 20 years and it’s pretty much been constant with some minor breaches and a little bit of pushing out,” he said.
“It is scary when you come across a site with a lot of jumping metamorphs all over the place.
“At the end of the day you don’t get them all.”
Mr Lenton said the CVCIA collected cane toads most weekends across the Clarence, but they continued to thrive.
“In recent years our level of effort has increased a lot, so we’re hopeful some of the extra effort we’ve been putting in will make a difference eventually,” he said.
“We put in thousands of volunteer hours, but there are areas we can’t cover effectively, so there’s really no end to the amount of effort that could be put in to control the pests.”
About 3,000 cane toad metamorphs were caught at Maclean, in the Clarence Valley region of northern New South Wales. (Supplied: CVCIA)
Containment is crucial
University of Sydney cane toad researcher Matthew Greenlees said he was confident conservationists were keeping the pests contained to northern New South Wales, but said the toads appear to be spreading across the Clarence Valley.
A cane toad’s cardiotoxin proved deadly for this young carpet python. (Supplied: Pamela Gray)
“They’re definitely holding the line east of the Pacific Highway,” he said.
“Cane toads have been stablished around Yamba since the 1970s.
“Unfortunately, more recently the natural spread of toads from where their main distribution is in northern New South Wales and southeast Queensland is starting to catch up with that isolated population that has been in Yamba for some years.
“We think they might actually be starting to spread faster and further than where these guys have managed to contain them most recently, which is a concern.”
Dr Greenlees said it was crucial to stop the spread of cane toads along the east coast.
“We saw a lot of species in northern Australia get severely impacted when toads moved through that area, but it’s a lot more homogenous, so you get the same species across a lot of northern Australia,” he said.
“Whereas if you’re moving down the east coast the diversity changes very rapidly with latitude, so you could have a lot more [native] species impacted over a shorter distance.
“The species on the east coast are the ones under pressure from development and humans because the population is so dense, so having an additional threat to them like the cane toad is another nail in the coffin for some of the really rare and threatened species.”
Dr Greenlees said researchers were working to establish more sophisticated ways of eradicating cane toads, rather than catching them by hand.
“These guys [in the Clarence Valley] have been really successful because they’ve been working in a small area, but the logistics of getting people on the ground to physically pick up toads gets out of hand really quickly in terms of how easily you can manage it,” he said.
“It’s an ongoing battle.
“In northern New South Wales it’s important to maintain an effort in controlling them to stop them spreading further south.
“We have to start looking at other strategies, like the work being done in North Queensland on trapping, and the lab group I’m involved in, which is working with chemists on trying to get an attractant for tadpoles so we can trap them.”