Australian dwarf crocodiles, whose normal food sources are rapidly vanishing, have begun
eating cane toads instead. But this new diet is killing them.
The cane toads were introduced in Australia from their homes in Central and South America in
1935 to help control beetles threatening the island’s sugar cane industry. Now it is estimated
that there might be as many as 100 million of these large amphibians scattered throughout
Australia and they are now considered a dangerous pest.
In 2012, many volunteers signed up to cull these toads, which are threatening not only dwarf
crocodiles, but other reptiles as well, including goannas, snakes and quolls. The toads secrete a
toxin from glands located behind their eyes and on their backs.
The deaths of the freshwater crocodiles and other predators may produce a cascade of
unpredictable ecosystem changes. This is typical when a new species is produced into a more-
or-less stable ecosystem. Another example of this problem arose from the introduction of giant
snakes into the Florida Everglades.
Apparently young crocodiles are more vulnerable to the cane toads’ venom than adults, which
will almost certainly affect future populations of the dwarf crocodiles.
The cane toads appear to be expanding south into the dry interior of Australia, where they will
encounter crocodiles and other predators at water holes. There is a bit of hope, however, in that
surviving crocodiles may develop a higher tolerance for the cane toads’ toxin. Some
blacksnakes, which had previously been hit hard by the toads, appear to have developed some
immunity to their poison.
Researchers are carefully monitoring the populations of both cane toads and crocodiles, hoping
to be able to predict the long-term effects of this rivalry on the Australian ecosystems.
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