November 21st, 2013
An unprecedented 10-year-study by the U.S. Fish and Wildlife Service shows encouraging results for frogs and toads on national wildlife refuges.
The study, published November 18 in the peer-reviewed online journal PLOS ONE, finds that on average, less than 2 percent of frogs and toads sampled on 152 refuges had physical abnormalities involving the skeleton and eyes – a lower rate than many experts feared based on earlier reports. This indicates that the severe malformations such as missing or extra limbs repeatedly reported in the media during the mid-1990s were actually very rare on national wildlife refuges.
“Frogs and toads are strong indicators of wetland and environmental quality. What affects them affects a broad range of other species,” said Service Director Dan Ashe. “This research significantly advances our understanding of amphibian abnormalities while amassing one of the world’s largest datasets on the issue.”
The study also highlights areas of the country with more abnormal frogs than expected. These areas, termed “hotspot clusters”, warrant further research to determine their causes.
Concern about amphibian abnormalities became widespread in 1995 when middle school students discovered frogs with misshapen, extra or missing limbs at a Minnesota wetland. Since then, scientists have continued to report frogs and toads with severe abnormalities and documented global amphibian population declines, disease outbreaks and an increased rate of species extinctions.