Suburban frogs said to be undergoing a gender revolution

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A female green frog is pictured. Credit: Geoff Giller/Yale University

We have come across reports of climate change being responsible for change in gender of reptiles and now a new study suggests that increased estrogen levels in suburban yards is driving up the numbers of female frogs while lowering the number of male frogs.

Pegged as a gender revolution in green frogs, the latest finding suggests that change in estrogen levels in areas where there are shrubs, vegetable gardens, and manicured lawns are disrupting frogs’ endocrine systems thereby resulting into higher number of female frogs and decline in male frogs.

For the study researchers conducted tests at 21 ponds in southwestern Connecticut keeping into perspective the varying degrees of suburban neighborhood impact. To this end, they analysed ponds that were entirely forested through to ponds that were heavily surrounded by suburbia. The sites included ponds linked to both septic systems and sewer lines.

“In suburban ponds, the proportion of females born was almost twice that of frog populations in forested ponds,” said lead author Max Lambert, a doctoral student at the Yale School of Forestry & Environmental Studies. “The fact that we saw such clear evidence was astonishing.”

Lambert added that their work showcases that for a frog, the suburban environment is very similar to farms and sewage treatment plants. According to researchers some plants commonly found in lawns, such as clovers, naturally produce phytoestrogens. The simple act of maintaining a lawn, in other words, may be one source of the contamination.

The researchers didn’t look at the possible causes of this because the potential relationship between lawns or ornamental plantings and endocrine disruption was unexpected.

Researchers add that there could be other implications for other species that use suburban ponds including other amphibians, such as wood frogs, spring peepers, gray tree frogs, and salamanders, as well as birds, turtles, and mammals.

“Some of our lab’s current work is trying to understand how the suburbs influence sexual development in other species,” Lambert said.

The latest study sits in line with previous studies which have shown gender revolution caused by agricultural pesticides and wastewater effluent.

The findings have been published in the journal Proceedings of the National Academy of Sciences.