First, the ecological impact of Cane Toads - which
turns out to be less wide-ranging and long term than
most people imagine. And second, toad control - what
works, and what doesn’t work.
like a hungry child offered a chocolate cake. And no
matter how many toads they ate, the rats just smiled
and kept eating more. Kites enthusiastically leap out of
bed in the morning to patrol the highways for an
effortless smorgasbord of road-killed toads.
The ecological impact of Cane Toads in
Australia.
As a result, the arrival of Cane Toads in a new area of
Australia is good news for some types of native
animals, even though it’s undeniably terrible for others.
People love to blame Cane Toads for just about
Let’s deal with the bad news first. The victims of the
everything. When the Federal Government announced
Toad are the large predators - species like goannas,
an inquiry into Cane Toad control late in 2018, the
blue-tongue skinks, King Brown Snakes, Northern
chairman of the committee put out a public statement
Quolls, and even Freshwater Crocodiles. The first
saying that, ‘Cane Toads are toxic at all points in their
toads to arrive – the vanguard of the invasion - are
life cycle, … with no known predators in Australia.’
really big animals. Any predator that eats one of those
He was wrong on both points. Toxin content is close
giant toads is dead within minutes, unless it has the
to zero at the point in the life cycle where toads
genetic ability (as in rats and birds) to handle the
metamorphose from tadpoles into miniature toads.
toxins. As a result, more than 95% of the apex
Presumably for that reason, predatory snakes (like
predators - notably the goannas - are dead within a few
Green Tree Snakes) target these tiny toadlets, snaffling
months of the appearance of toads. Catastrophe. It’s
them up like popcorn - but the snakes are very
awful. But as I said, other groups benefit from toad
reluctant to eat either younger tadpoles or larger
arrival. First are the ones that are not affected by the
terrestrial toads (both of which contain a lot more
toad’s poison, like birds and rodents. Suddenly they
poison). And importantly, many species of wildlife in
have a new (and very abundant) source of food. The
Australia are very resistant to the Cane Toad’s toxins.
second group consists of smaller species that were pre-
For example, most birds and predatory insects aren’t
viously being consumed by those apex predators that
affected. Neither are rodents (rats and mice, both
have now gone belly-up after meeting a toad. With no
native and introduced). When we tested native rats,
greedy goannas left to eat them, prey numbers
they hurled themselves upon Cane Toads (of any size)
increase.
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