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Suburban Frogs

September 17, 2015

Genetically male tadpoles could be turning into female frogs because of the plants in your own backyard.



montage green frogs

A suburban house near a pond, a green frog in metamorphosis from tadpole to adult frog, and an adult male green frog in a pond. (Max Lambert and Geoff Giller)

Frogs in suburbia. I’m Bob Hirshon and this is Science Update.

In Connecticut’s forested ponds, more male green frogs are born than females. But head to the suburbs, and the sex ratio reverses itself, according to Yale amphibian ecologist Max Lambert.

MAX LAMBERT (Yale University):

That pattern was remarkably strong; it was unexpected.


Lambert and his colleagues write in the Proceedings of the National Academy of Sciences that plant hormones called phytoestrogens are likely turning genetically male tadpoles into frogs with female ovaries.


We are finding a whole diversity of phytoestrogens that are consistently found only in people’s backyard ponds, and never in these natural forested ponds.


Common suburban plants like clover produce phytoestrogens in their roots, and Lambert suspects that runoff from lawns could be carrying the chemicals into ponds. The researchers are now investigating how chemicals given off by different plants impact sex ratios in tadpoles. I’m Bob Hirshon, for AAAS, the science society.