Estrogen in Wastewater Bad News for Male Frogs

A news study has found that ponds in suburban areas have almost twice the proportion of female frogs to male frogs than isolated, forest-bound ponds. The estrogen in suburban wastewater disrupts frogs’ reproductive systems, causing them to spawn far more female frogs than male frogs, and in effect, threatens the entire species and ecosystem.

The study was done by Yale University and compared the proportions of frog sexes between 21 suburban ponds and isolated ponds in southwestern Connecticut. Its findings were published in the latest issue of the journal Proceedings of the National Academy of Sciences.

End of an Era for Male Frogs

In the wild, the study found, male frogs outnumber female frogs, accounting for almost 60 percent of the frog population. But in suburban areas, it’s a different story: female frogs account for more than 60 percent of frog populations, nearly doubling the rate of male frogs.

Some of these frogs have even been shown to change sex, or become hermaphroditic. Scientists found female eggs in the testicles of many male frogs in suburban areas.

So What’s Causing This? Suburban Housewives?

Actually, the estrogen that is bringing about so many female frogs has nothing to do with the female humans who live nearby. But it has everything to do with clovers.

Clovers? Yes, clovers are just one of several common lawn plants that naturally produce “phytoestrogens.” When plants like clovers occur in unnatural concentrations as they do in the grassy suburbs, phytoestrogen levels in water become high enough to alter the biology of water-bound animals.

Amphibians are especially susceptible. While the study focused on green frogs as a common North American amphibian species, the same results are predicted for toads, newts, and salamanders. Further studies will investigate whether these phytoestrogens are even affecting the reproduction of birds and mammals.

Burn the Clovers! Burn Them All!

Well, it’s not that simple. The problem is, clovers and other lawn flora are not the only things causing frogs to birth females at such high rates; they are only the most surprising discovery of the study.

A dearth of male frogs had already been observed in ponds surrounding commercial farms and sewage treatment plants. The cause: pesticides, mostly. This latest study of suburban ponds was designed to see whether pesticide usage was high enough in suburban areas to affect frog sex. It accidentally discovered the phytoestrogen, reaching the ominous conclusion that simply having a lawn is a threat to frog and amphibian populations, pesticide or not.

Well Good Riddance, We’ve Had Enough of Men Already!

I would like to agree, because I think that we males don’t do a whole lot of good for the world. But there’s one thing you can count on us for: having sex with females. If we got rid of men, we’d have about 80 years of world peace until all the women died off. Tempting, but impractical.

It’s the same story for frogs. If we don’t find a way to reverse these falling rates of male frog births, we may be saying goodbye to our ribbit-ing friends and the entire ecosystems they support.

What do you think is the solution to this male frog crisis? Share your wisdom!


Not the male frogs! Lend Mother Nature a helping hand and preserve it while you can:

Kerry Martin is a semi-native of Denver. He went to school in Vermont for its great beaches. Now transplanted to Brooklyn, he works as a volunteer coordinator/community organizer for ArchCare TimeBank when he isn't writing Ecology, Technology, and Offbeat articles for Clapway.