The most common types of ingested birth control contain estrogen. But the hormone doesn’t just prevent human babies. It may be lowering numbers of frog babies, too. Because estrogens can travel unaltered through a woman’s system, and back into the environment—where they interfere with the courtship of frogs.

 

Researchers bathed male frogs in tanks containing various concentrations of estrogen—comparable to levels previously measured in nature. And they found that males exposed to estrogen made significantly fewer ‘advertisement’ calls: mating calls that say “hey ladies, I’m over here.” Instead, the frogs made more so-called ‘rasping’ calls: a sign the boys weren’t as turned on as they used to be.

 

As it turns out, neither were the ladies. Because when researchers played back estrogen-influenced calls to females, the lady frogs weren’t as hot to hop, compared to when they heard the crooning of control frogs. Those findings appear in the journal Public Library of Science ONE. 

 

The authors say less seductive mating calls could mean fewer tadpoles. Which means our sex lives could be partly to blame for making global populations of amphibians croak.

 

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