A warts-and-all way to kill cane toads humanely – without the “zombie” effect

Dusk is prime hunting time, when toads venture into easily accessible areas—grassy backyards, pathways, parks, ovals—in search of food. They love well-lit rooms because the light attracts moths, which they like to eat.

Then it’s a simple case of packing the toads, putting them in the bucket, chilling them in the fridge and finally euthanizing them in the freezer.

It’s important not to skip the fridge step because freezing toads directly will cause them pain, Vincent warns.

Putting them in the fridge first cools them and sets them to solidity, a state that’s a bit like hibernation and involves a slowdown in bodily functions.

Australian researchers who implanted data loggers in the brains of cane toads a few years ago discovered that those chilled in the fridge for a few hours registered no sign of pain when later placed in the freezer.

The fridge-then-freezer approach also appears to stave off the likelihood of the so-called zombie-toad encounter.

“We’ve had occasions where frozen toads have been brought to us by members of the public, and then they’ve been in our freezer for a week, but once we got them out and started thawing, they woke up,” she says.

Emily Vincent of environmental organization Watergum advises toad hunters to put them in the fridge to set them to solidity before putting them in the freezer.

Emily Vincent of environmental organization Watergum advises toad hunters to put them in the fridge to set them to solidity before putting them in the freezer.Credit:Emma Young

“We know amphibians can do that, they can freeze themselves and wake up. We contacted the university to ask about it.

“If that happens, they suggested, they may have been frozen very, very, very quickly and not refrigerated before freezing, and that means they’ve been self-preserved.”

Strange as it may seem, Watergum welcomes regular shipments of frozen toads collected by Australian eco-warriors.

The venom stored in the glands on the toad’s neck holds the key to a new weapon of mass destruction that targets cane toad tadpoles.

A few years ago, the University of Queensland’s Institute of Molecular Bioscience and Professor Rick Shine of the University of Sydney figured out how to turn tadpole behavior and cane toad venom against them.

When tadpoles hatch in rivers, streams, dams, or ponds, they are seized with an impulse to seek out and eat the eggs laid by other females. They do this by following the scent of pheromones present in the cane toad’s toxin.

“Gravity toad eggs are coated with pheromones by the female as they lay them. She basically coats them with a secretion that contains the toxin. We think this protects the eggs from predators,” says Vincent.

“And we know that when tadpoles pick up that pheromone scent, they’ll follow it.”

Research shows that the pheromones can be isolated from venom glands harvested from dead toads and used to make tadpole bait.

The commercialization of the baits has been entrusted to Watergum, which expects the baits and tadpole traps to go on sale in the first few months of this year.

“In the lab, we isolate this pheromone and discard everything else. Then we apply it to a slow-release capsule and that creates our bait,” says Vincent.

“This bait goes into a trap that is placed in the water. The pheromone scent spreads and leaves a trail, and any tadpoles present follow it and end up in the trap.”

Crucially, the bait doesn’t attract other species, so it doesn’t pose a threat to native frogs or toads.

Vincent says baiting is an excellent second line of defense, but collecting adult cane toads before they have a chance to breed is the most successful method of control.

“We can now use these adult toads and turn them into bait to catch tadpoles produced by any we’re missing. It’s a nice big circle of control.”

An announcement as to when the baits and traps will go on sale is expected in the coming months.

Toad carcasses that cannot be sent to Watergum for toxin harvesting may be disposed of in roadside dumpsters.

The 2023 Great Cane Toad Bust is taking place January 23-29 in all states and territories where the toads can be found.

For details on how to participate, see watergum.org/greatcanetoadbust/


https://www.smh.com.au/national/a-warts-and-all-way-to-kill-cane-toads-humanely-without-the-zombie-effect-20230114-p5ccif.html?ref=rss&utm_medium=rss&utm_source=rss_national A warts-and-all way to kill cane toads humanely – without the “zombie” effect

Callan Tansill

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