release small Cane Toads just in advance of the
invasion front. It’s easy to find sites where invasion is
bound to occur within a few months. Predators such
as goannas eat those small toads, get sick, and avoid
toads thereafter. So when the invasion front arrives,
those educated predators don’t try to eat the (large)
toads in the invasion vanguard; they already know
that toads make you nauseous. As a result, the
predators survive.
But what happens next? Unlike quolls, reptiles don't
teach their young how to forage, so mum can’t teach
the babies to avoid Cane Toads. Does that mean that
training predators is a waste of time - saving one
generation, only to have their offspring die instead?
No. Within a year or two of arriving in a site, the
toads begin to breed - producing hordes of tiny
amphibians that can serve as perfect ‘teachers’ for the
offspring of any predators that survived the initial
onslaught. One generation of education is all we need
to blunt the impact of the toad invasion. Some
luckless individual may still die if the first toad it
encounters is too big. But this loss is more than offset
if the predator’s brothers and sisters survive long
enough to reproduce.
A few years ago, when I suggested releasing small
toads in advance of the main toad invasion, the
general reaction was negative. And that’s putting it
mildly. People in the path of the toad invasion
thought that this was quite the most stupid idea they
had ever heard. Except, they didn’t phrase it quite as
politely as that. But things changed when we did the
experiments to test the concept. We trained young
quolls not to eat toads, and those quolls survived.
Tragically, their untrained siblings died as soon as they
encountered their first toad. We trained blue-tongue
skinks not to eat toads, and they survived. Other
skinks, treated the same way except for the training,
were all dead within a few weeks of toad arrival.
Yellow-spotted Goannas that we trained to avoid
toads survived, despite being surrounded by toads a
few months later, whereas untrained goannas died.
Again and again, the idea worked. And so, opinion
shifted. More and more people decided it was worth a
try. Most importantly, my student Georgia Ward-Fear
worked collaboratively with Aboriginal groups in
implementing the method, building strong support
from the traditional owners of important sites in the
Kimberley.
So, it’s happening. An idea that sounded like lunacy
(“WTF!!! some southern boffin wants to release MORE
bloody Cane Toads!!??”) won across-the-board support,
and we are working with a coalition of conservation
groups to implement Conditioned Taste Aversion