Lesley Smitheringale Fine Art

Garden Guests Diary - The Unwanted Amphibian [20 March 07]

This Cane Toad has been keeping me awake for the last week or so with his repetitive croak and he has decided to make our fish pond his home. I spotted him this morning when I was feeding our goldfish and I took a photograph of him resting on the side of our pond. This is one ugly critter and he is hated by all Aussies which you can read about in the short article I have included below.

Up until 1935, Australia did not have any toad species of it’s own. We had tree frogs and burrowing ground frogs - even microhylid frogs which do not have a tadpole - but none of the world’s hundreds of toad species evolved here. However, not wanting to be left out, Australia acquired some - 102 toads, in fact.

These toads were supposedly being used successfully in the Carribbean islands and in Hawaii to combat the cane beetle, a pest of sugar cane crops. After rave reviews from overseas, Hawaii shipped a box of toads to Gordonvale, just south of Cairns. These were held in captivity for awhile, their numbers were increased by breeding, and then they were released into the sugar cane fields of the tropic north. It was later discovered that the toads (scientific name Bufo marinus) can’t jump very high so they did not eat the cane beetles which stayed up on the upper stalks of the cane plants. At the time of year when the beetle’s larvae were emerging from the ground, no toads were about. So the cane toad, as it came to be known, had no impact on the cane beetles at all and farmers had to go back to the use of chemicals to kill the beetle.

Meanwhile, the ‘cat was out of the bag’ or, more accurately, the toads were out of the box! But there were only a few hundred of them so nobody gave any thought to catching them up again and disposing of them. The toads were on their own and they proved to be very hardy survivors. They turned out to be a lot more than we bargained for and it didn’t take long to find out how well the toads would do in their new Australian home.

They breed like flies, as the saying goes. Each pair of cane toads can lay 33,000 eggs per spawning (some published references estimate they produce as much as 60,000 eggs!). Their ‘toadpoles’ develop faster than many Australian frogs so they can outcompete our frogs for food. oads and toadpoles seem to be resistant to some herbicides and eutrophic water which would normally kill frogs and tadpoles.

All stages of a toad’s life are poisonous so they have no natural predators to keep their numbers in check (although Mike Tyler’s work suggests that toad juveniles are not toxic until they reach about 3cm in size but this presents a question: why would an animal lose its toxicity at the juvenile stage when it has it during larvae and adult stages?)
Toads not only eat the food normally available to Australian frogs, there is growing anecdotal evidence that they eat frogs as well, especially metamorphs.

Info from - http://www.fdrproject.org/pages/toads.htm