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