How does this all work then? What is it about these lures that is so tempting to cane toad tadpoles?
Discovery of the Technology
Intent on finding a more successful way to control and reduce cane toad numbers, a team of dedicated scientists spent time observing cane toad tadpoles and their behaviour.
They discovered that cane toad tadpoles are cannibalistic! Once they hatch they immediately seek out cane toad spawn to snack on. Even in large waterbodies, the tadpoles seemed to know exactly where to go to find spawn to predate, and scientists soon realised that they were following the scent of cane toad toxin, which is coated on the eggs as they are laid by the mother to act as a protective shield against predators. The tadpoles can detect the scent of the toxin as it seeps into the water around the spawn. By eating the spawn of other females, cane toad tadpoles eliminate their competition and perhaps also boost their own toxicity levels.
Toad spawn can be difficult to find and collect so studying it would have been challenging. However, the toxin that coats the spawn is the same toxin that resides in the parotoid glands of adult toads and there’s plenty of them about! So the team collected some adult toads and harvested their glands to investigate further in their lab.
They found that the toxin was made up of several different chemicals and only one of these was attractive to the tadpoles, the adult toad pheromone. They were able to isolate the pheromone, and safely dispose of the rest of the material. On its own, the pheromone does not pollute the waterways and is not dangerous to wildlife, so it can be safely used as a lure!
This method of cane toad control is revolutionary as it targets cane toads at all life-stages and encourages members to remove all life stages from the environment. The lures catch the tadpoles, and we have to collect the adults so that we can continue to make the lures! It also ensures that all of that harmful toad toxin is safely removed from the environment. Once broken down in the lab, the waste material from the lure-making process is no-longer toxic so can be safely disposed of, and the toad bodies (minus their toxic glands) can be used to make great compost!
Discussion Point: What do you think? Do cane toad tadpoles predate the spawn of other females to eliminate the competition, boost their own toxicity, or simply feed themselves?