Road salt can change sex ratios in frog populations, study says

https://www.eurekalert.org/pub_releases/2016-11/ysof-rsc112116.php

Public Release: 22-Nov-2016
Road salt can change sex ratios in frog populations, study says
Naturally occurring leaf litter can also alter sex outcomes
Yale School of Forestry & Environmental Studies

Naturally occurring chemicals found in road salts commonly used to de-ice paved surfaces can alter the sex ratios in nearby frog populations, a phenomenon that could reduce the size and viability of species populations, according to a new study by scientists at Yale and Rensselaer Polytechnic Institute (RPI).

The researchers found that the proportion of females within tadpole populations was reduced by 10 percent when exposed to road salt, or sodium chloride, suggesting that the salt has a masculinizing effect.

They also found that exposure to fallen oak leaves also significantly altered the sex ratios in the frog populations, as well as the size of individual females in some cases. Maple leaf litter, on the other hand, had no effect.

More than 22 million metric tons of road salt is applied to roads in the United States each year. Maple and oak trees are dominant trees throughout temperate North America.

"Many scientists have studied similar effects from exposure to pharmaceuticals and pesticides, but now we're seeing it from chemicals found in common road salt and leaf litter," said Max Lambert, a doctoral student at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the paper.

"The health and abundance of females is obviously critical for the sustainability of any population because they're the ones that make the babies," Lambert said. "So if you have a population that is becoming male-based, the population might be at risk."

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