iHerp Australia Issue 11 | Page 11

impact of Cane Toads is (as I’ve said above) that they fatally poison large predators that try to eat them. And it only takes one Cane Toad to kill a big goanna. Even if you extirpated 99% of the local toads, your local goanna is highly likely to find the one you missed, eat it, and die. So the benefit to vulnerable predators is close to zero unless you can eliminate every toad. And that’s a well-nigh impossible task. In practical terms, how can you knock down toad abundances? The most popular method is to collect adult toads by hand at night, using a spotlight; some people use traps as well. ‘Toad-busting’ can remove a lot of toads, but this has only a temporary effect in most places. The reason is toad biology. A single female Cane Toad can lay 40,000 eggs in a single clutch, so the sad reality is that even if you thump 99.9% of the local toads on the head, the surviving 0.1% can replace all of the ones you terminated. Indeed, they can do it in a single rainy night. The only way to reduce toad numbers is to stop them from breeding. Fortunately, our research found a way to do this. We discovered that Cane Toad tadpoles are voracious cannibals. As soon as a clutch of toad eggs is laid in a billabong, any older Cane Toad tadpoles zero in on the new eggs and eat them. That way, they wipe out the competition before they become a problem. How does this help with toad control? Because the way that toad tadpoles find new egg masses is by searching for chemicals that exude from the eggs as they develop. Those chemicals are poisons - the same ones produced in the shoulder glands of an adult Cane Toad. So if we squeeze out poison from the glands of adult toads, we can use it as ‘bait’ in funnel traps that lure in thousands of Cane Toad tadpoles. It’s highly selective as well, because the tadpoles of native frogs are repelled, not attracted by the toad poison. Community groups across much of Australia are now using our ‘Team Bufo’ funnel traps with great success, hauling literally millions of toad tadpoles out of ponds and dams. Our collaborator Rob Capon, from the University of Queensland, is rolling out a major program for toad control to the general public, and is fine-tuning the ‘bait’. And once you’ve stopped the local toads from breed- ing, killing adult toads can have a big impact on total Above left: In the land of the ‘Big Banana’, the ‘Big Pineapple’ and the ‘Big Prawn’, the ‘Big Cane Toad’, located in Sarina, near Mackay, underlines the fact that the Cane Toad is now unmistakably here to stay. Thankfully, the town of Dunedoo in central NSW scrapped plans to build a ‘Big Dunny’. Image by Sain Alizada / Dreamstime.com Right: a female Cane Toad can lay 40,000 eggs in a single clutch, so removing adult toads only has a temporary effect in most places. Image by Aleksey Stemmer. abundances. Hand-collecting can be very effective, but when you’ve filled up your bag with wriggling toads (after checking carefully that they aren’t native frogs - a lot of which have been brutally dispatched by mistake!), how do you then kill them in a humane way? The best method is ‘cooling-then-freezing’. Pop the bag in the fridge for a few hours, then transfer it to the freezer. We measured brain activity in toads that were treated in this way, and they just drifted off to sleep before ending up as frozen toadsicles beside the ice cream container in the freezer. Therefore it’s a humane way to terminate them. So how should you deal with that irritating Cane Toad that hops across your back verandah? It isn’t protected by law, so you can legally dispatch it if you want to. As I mentioned earlier in this article, my own approach is to first consider that it’s not the toad’s fault that it’s here in Oz (no, it’s OURS), and also whether or not removing that toad will benefit the native wildlife (maybe, if you are also stopping toads from breeding in the local area, and if you live in a recently-invaded area). If you do decide to opt for extermination, then cooling-then-freezing is a far kinder option than smashing and bashing. We all wish that Cane Toads weren’t brought to Australia, and we are all dismayed at the sight of them around our homes and in the bushland. But attempts to massacre the toads have been remarkably ineffec- tive, despite the expenditure of millions of dollars and thousands of hours of community effort. Maybe we should rethink our approach? Reference Shine, R. 2018. Cane Toad Wars. University of California Press, Berkeley (available in Australia through Footprint Books). A review of Rick’s great new book, ‘Cane Toad Wars’ appears on page 29. The publisher would like to thank Cathy Miller, the ’singing quilter’, for providing an image of the Big Cane Toad, even though it was not ultimately used. Visit www.singingquilter.com