The most popular weedkiller in the United States can give male frogs female sex organs and other attributes, researchers said on Monday, in a study that could shed light on the global decline in amphibian populations.

Very low levels of the herbicide atrazine can cause male frogs to grow female sex organs and curtail their croaks — key to attracting mates in the frog world — a team at the University of California Berkeley found.
The frogs appear normal on the outside, but often have both male and female sex organs.