Indeed they are poisonous! Yes, they got to Australia from Central America, via Hawaii, in 1936. I guess there was a sugar cane conference somewhere in Central America in the late 20s or early 30s that was attended by A scientist from Australia where he learned about the toads helping kill the cane beetle locally, so that's where the idea started.
Turned out the cane beetle in Australia laid it's eggs in the flowering bud so they were two feet off the ground and the cane toads could not reach them. Tragic.
Here's the doc if you are interested...
