Pesticides may be creating hermaphrodite frogs, causing their population to dwindle

• Scientists who compared frogs collected over the past 150 years have discovered a dramatic increase in hermaphrodites during the times when contamination from the pesticide DDT and other organochlorine chemicals was widespread.
• Frogs with both male and female reproductive organs were rare in the 19th century and early 20th century but abundant during the 1950s, when the largest volumes of the popular chemicals were used.
• The findings were reported earlier this month in the journal Environmental Health Perspectives.
• The ability of chemicals to mimic or block estrogen and testosterone, critical for normal reproduction, is considered one of the most disturbing discoveries in environmental science of the past decade.
• Scientists believe the phenomenon has been occurring for decades but wasn't documented in wildlife until the early 1990s, when it was observed first in Florida alligators and then many other species.
• Toxicologists and veterinarians at the University of Illinois at Urbana-Champaign, led by Amy Reeder, examined the reproductive organs of 814 cricket frogs collected in Illinois between 1852 and 2001 and stored at natural history museums.
• Cricket frogs, once abundant, declined dramatically around Chicago and other regions in the 1960s, and the scientists found that the times and places with high rates of hermaphrodites, also called intersexes, overlapped with when and where the frogs disappeared in Illinois.
• The scientists theorize that DDT, PCBs, and other contaminants had an anti-estrogenic effect, reducing the proportion of females and causing them to develop skewed sex organs, triggering a population crash, particularly in the Chicago region.
• "These guys have been around a long time, since before the dinosaurs, and they are declining all over the place," said Val Beasley, a co-author of the study and a professor of ecotoxicology at the university's College of Veterinary Medicine.
• "Endocrine disruptors seem to be a factor, but certainly not the only factor."