Cane toads (Rhinella marina) were introduced to Australia in 1935 and continue to cause damage to ecosystems. (Image credit: edelmar via Getty Images)
Australia plans to launch a massive annual cane toad eradication campaign – known as the Great Cane Toad Dying – in an effort to reduce the numbers of the invasive pest. Now, scientists are proposing a humane way to eliminate the toxic toads.
Instead of hitting cane toads (Rhinella marina, formerly Bufo marinus) with cricket bats and golf clubs or poisoning them with harsh chemicals, scientists recommend bagging the toads and placing them in a refrigerator. The cold puts the amphibians into a state of torpor and disables their pain receptors. People can then move the toads to a freezer to humanely end their lives, said Rick Shine, a biology professor at Macquarie University in Sydney, Australia.
“When a toad gets cold, its metabolism slows down and it becomes extremely inactive,” Shine explained in an email to Live Science. “Even its brain shuts down. So a cold toad doesn't feel pain, and it never realizes what's happening — it just goes to sleep and never wakes up.”
Cane toads naturally tolerate lower temperatures at night, so their bodies don’t go into shock when they’re first placed in the refrigerator, Shine noted. In a 2015 study, Shine and his colleagues found that the toads’ brain activity gradually declined during freezing and didn’t produce any detectable pain signals. By the time ice crystals begin to form in the toads’ tissues, “they’re not aware of anything,” he added.
Scientists introduced cane toads from Hawaii to Queensland, Australia, in 1935 to control cane beetles (Dermolepida albohirtum) that were ravaging newly planted sugar cane fields. However, the effort backfired, as the cane toads showed no interest in the beetles and multiplied out of control. The toads, which secrete a poison that can kill animals that eat them, spread along the coast of New South Wales, the Northern Territory, and parts of northwestern Australia. Wherever they appeared, native predators declined and ecosystems deteriorated.
Cane toads continue to be a problem, prompting environmental nonprofit Watergum to organize the Great Cane Toad Bust, an annual campaign to kill as many of the toads as possible in a week. This year’s kill-athon—the third nationwide event and the first to target both tadpoles and adult toads—runs from January 13 to 21.
“The Great Cane Toad Invasion is the largest toad infestation in Australia,” Nikki Thomsett, Watergum’s invasive species project manager, told Live Science in an email. “It’s all about collective action to effectively and humanely control cane toads, which are an invasive pest species in Australia.”
The campaign is already showing success: People have removed more than 50,000 cane toads from their habitat in one week, Thomsett said. “We’re aiming to set a new record this year,” she added.
Cane toads can live more than 10 years in the wild, Thomsett said. Female toads lay up to 35,000 eggs each time they reproduce, meaning every toad counts when it comes to pest control.
The freezing and chilling method is “currently considered best practice for humanely euthanizing cane toads,” Thomsett said. “Blunt trauma and most chemical methods are not considered humane and pose a risk to wildlife and domestic animals, as cane toads euthanized in this manner typically remain in the environment and remain toxic after death.”
“People who club the toads to death also risk piercing their venom glands, which can cause temporary blindness in humans,” ABC News reports.
Sourse: www.livescience.com
