A COMMON weed killer is making toad tadpoles "beef up" their weaponry, a study has found.
Hungarian researchers have discovered that the presence of glyphosate, a chemical commonly found in backyard weed killers such as Roundup, increased the amount of poison the tadpoles produced when they developed into toads.
Cane toad expert Rick Shine from University of Sydney said toads in Australia likely had the same type of reaction.
"We know that toads ... are incredibly flexible and tadpoles seem to assess how difficult the world is based on chemical cues they get from the environment," Professor Shine said.
"They are the kinds of cues the tadpoles would normally use that would give them an indication that look, there is a danger here and it is a dangerous world, I need to spend a bit more of my resources on beefing up my weapons.
"We know that if they think they are under attack from predators that they will invest more in weapons, their chemical defences, so when they turn into small toads they grow larger poison glands and they change the type of poison and amount."
Professor Shine said the international study, which was published in Proceedings of the Royal Society B on Wednesday, found chemical pollutants were having the same effect on tadpoles as natural chemicals found in ponds.
"If you put a dragonfly larvae in the water, even if it can't get at the tadpoles, the tadpoles detect chemicals from the predatory dragonfly larvae, because they love to eat tadpoles, and that will cause them to change their investment into poisons," he said.
"If you crush up toad tadpoles and put that in the water, which basically tells a young tadpole that someone is eating your brothers and sisters, that will strongly increase the amount of poison that the young toad will begin to produce after it transforms into a little toad."
While the study made a direct link between the presence of glyphosate and an increase in poison found in adult toads, Professor Shine doubted it would have a major effect.
"In areas where toads have been present for long periods of time, most of the native predators either simply don't eat them or are capable of dealing with the poison, so it would just make lunch a little spicier than it would otherwise have been," he said.
"At the invasion front, toads are catastrophic. They poison native predators and so under that circumstance, a smaller toad might have enough poison to give you a heart attack rather than make you sick (but) I doubt it is going to have a major effect.
"I think it is a fascinating insight into the flexibility of toads but I would doubt that it will really have a substantial impact on their ecological impact in Australia."
