Researchers led by David Skelly from Yale University discover that the estrogenic waste found in suburban ponds might be the cause for the lack of male green frogs and the increasing number of female frogs.
The study appears in Proceedings of the National Academy of Sciences and consists of tests conducted at 21 different ponds around Connecticut. Researchers sampled numerous green frogs and the results were surprising to say the least: the suburban ponds had almost twice as many females as males, while the female frogs from forest ponds were in minority.
Previous studies conducted by researcher David Skelly found that male frogs often had female characteristics, such as males whose testicles developed eggs. These hermaphroditic traits have been linked to the herbicide atrazine and agricultural chemicals.
Max Lambert doctoral student at Yale University suggests that estrogenic chemicals can also be produced by plants such as soybeans, clover, peanuts, etc.. These chemicals are able to mimic estrogen and thus affect the sexual development of not only frogs, but also other animals. The simple act of removing native plants by mowing the lawn could lead to such contamination.
Chemicals that have the effect of debilitating the hormonal development are called endocrine disruptors. “This shows that endocrine disruption is a much more diverse phenomenon than we previously realized,” suggests Lambert.
The study also found evidence of other estrogenic chemicals called estrones, which do not come from plants but humans and other animals.
Brad Shaffer, a researcher at UCLA says that the study conducted by Shelly’s team is extremely important in making people realize the damage that suburbanization brings to the natural ecosystems. He also mentions that since amphibians are very sensitive creatures, they can easily be affected by changes in the environment.
About 20 years ago scientist Theo Colbrom brought up in her book the issue of humans distorting the environment and thus disrupting the natural development of animals such as frogs. Even though at the time there was no strong evidence to back her arguments, studies such as the one from Yale University are beginning to show that Colbrom was right.
Image Source: naturallycuriouswithmaryholland.files.wordpress