Frogs can change their sex even in pristine, pollution free settings. Past research suggested that male-to-female sex changes happening in frogs in suburban ponds may be caused by increased levels of estrogen released into the water. They found more female frogs than males in suburban areas. But now a new study by the same scientists finds that green frogs (Rana clamitans) change sex even in natural, unadulterated settings relatively free from human-caused pollution. The authors of the study speculate that the frogs are instead reacting to local changes in temperature or other environmental factors. As far as they know, frogs can only change sex during their tadpole phase.
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