Ant
Your one and only pest!
In Australia they believe they can use the native meat ant to kill of the young toads as they morph into adults. Its very interesting, and a very good idea. Also it has a little pun in their, ants DO have hearts, just the toads toxin can't harm them.
http://www.theaustralian.news.com.au/story/0,25197,25267214-5013404,00.html
http://www.theaustralian.news.com.au/story/0,25197,25267214-5013404,00.html