Researchers at Yale University has studied about green frogs in southwestern Connecticut’s nearby ponds and concluded that estrogen, a group of steroid hormones that promote the maintenance/development of female characteristics of the body, in suburban yards are influencing the gender ratio of these green frogs.
According to the study, the number of female frogs is increasing due to the excessive estrogen in nearby vegetable gardens, shrubs and manicured lawns. Estrogen, believed to be the main factor disrupting suburbs’ green frogs’ endocrine systems.
Yale University’s Max R. Lambert, Geoffrey S. J. Giller, David K. Skelly, and U.S. Geological Survey’s Kevin C. Fitzgerald and Larry B. Barber co-authored the research, which is published in the Proceedings of the National Academy of Sciences. This research is based on the studies conducted at 21 ponds in southwestern Connecticut in 2012.
Scholars conducted similar studies a few years back, which showed the disruption of these green frogs due to the effects caused by wastewater effluent and agricultural pesticide. However, the new research concludes the effects of amphibian endocrine disruption in suburban areas.
Lead author Max Lambert, a doctoral student at the School of Forestry and Environmental Studies, Yale University, New Haven, CT, said in a statement:
“In suburban ponds, the proportion of females born was almost twice that of frog populations in forested ponds. The fact that we saw such clear evidence was astonishing. Our work shows that, for a frog, the suburbs are very similar to farms and sewage treatment plants. Our study didn’t look at the possible causes of this, partly because the potential relationship between lawns or ornamental plantings and endocrine disruption was unexpected.”
The researchers selected two kinds of ponds to study about the impact of the suburban neighborhood – ponds with heavily surrounded suburbia and ponds with entirely forested surroundings. Even they have considered the septic systems and sewer lines when doing the research. Even they had to take permission from homeowners to survey the ponds in their backyards.
How do estrogen reaches green frogs?
According to the study, clovers-like plants commonly found in lawns are one of the source of the contamination, which produces phytoestrogens naturally.
There also are possible implications for other species that use suburban ponds, note the researchers. Those species include other amphibians, such as wood frogs, spring peepers, gray tree frogs, and salamanders, as well as birds, turtles, and mammals.