How did a “snake and lizard guy” become interested in cane toads?
Professor Richard Shine from the University of Sydney has spent decades researching the ecology and evolution of his favourite subject, Aussie snakes, to much acclaim both at home and internationally.
But ten years ago his career took a somewhat unexpected turn. Shine had been conducting field trips to the Adelaide River floodplain near Darwin for 20 years - and then the cane toad invasion front arrived.
The impact on the local ecology was severe, threatening to wipe out the very snakes Shine was studying. Thus he realised that the team needed to take a closer look at toads to find out what exactly they’re doing to thrive - and to gain knowledge on how to hamper them.
“A cane toad is a giant Brazilian rainforest frog hopping across the driest continent in the world, so they have vulnerabilities we can use,” he explains.
Shine’s team started with what he calls “basic field research” on these pests, and the insights they gained on tadpole behaviour led to the development of a highly successful trapping method.
“They’ve evolved for 20 million years in competition with other cane toads, and have devised weapons to attack them, so all we have to do is listen in on their weapons plan,” says Shine.
It turns out that cane toad tadpoles are cannibals. Their ‘weapons plan’ consists of detecting chemicals present at toad egg clutch sites, swimming over and gobbling them up. Using poison from the shoulder glands of adult cane toads, Shine and his team devised an efficient trap which tadpoles swam right into, expecting a hearty meal.
“A single female toad can lay 30,000 eggs, so we need to stop them from breeding,” he notes. The method enables researchers to wipe out an entire cane toad egg site once it’s discovered, leaving no survivors to grow into a next generation of adult toads.
Best of all, the poison-laced traps attract nothing else. “Native frog tadpoles detect it and go the other way,” says Shine.
Fighting poison with poison
Professor Shine explains the cane toad invasion is not all dire news.
“Contrary to what you hear, there is a lot of native wildlife that doesn’t die from eating cane toads - lots of birds, rodents, rats in particular, insects are not affected by the cane toad poison,” he notes, explaining that for these species cane toads amount to a wonderfully abundant food resource.
But some of our species are at grave risk. Native Aussie predators - such as the critically endangered northern quoll - go for the fattest, biggest toads, ingesting huge amounts of poison. In this way entire populations have been decimated by this attractive and deadly new bait.
And here lies the latest breakthrough by Shine and his team - they have taught these predators that cane toads are bad food by introducing them to small doses of the sickening meal.
If you think back to a nasty bout of food poisoning that put you off the dish responsible, it’s the same principle - known as behavioural conditioning.
“When I was 17, we went camping and someone brought a bottle of scotch - I drank way too much, and to this day the smell of scotch makes me nauseated,” says Shine.
The same happens to a quoll if they eat toads small enough to not be deadly - the intense nausea and the general feeling of “I might die of a heart attack” successfully conditions against treating cane toads as prey.
Shine’s team used conditioned taste aversion to create “toad-smart” quolls at the Territory Wildlife Park south of Darwin. Their hope is to create a program that will allow for a release of these toad-hating predators in areas where the cane toad invasion front is still coming, and thus protect them from harm.
“Cane toads are here to say forever. But if we can buffer this then we’ve come a long way to protecting native wildlife in Australia,” says Shine, adding that it’s an exciting time now that they’re figuring out the details of the program. Whether they’ll release actual baby cane toads or use “cane toad sausages” is still to be determined.
This years Prime Minister’s Prize for Science adds to an extensive list of Richard Shine’s accolades. In fact, he is the only person to ever win the Australian Museum Eureka Prize in three different categories - for promoting science to the public, for biodiversity research, and for mentoring young researchers.
“They know more about wildlife than I do, they work harder than I do,” Shine says of the young scientists who work alongside him on these biodiversity and conservation projects.
Still, he accepts the prestigious prize as a great honour, and is happy to see that there’s still a place for “straightforward field science” reminiscent of Charles Darwin’s times.
“I don’t even own a white lab coat,” he laughs.