Landmark Study Reveals Low National Rate Of Frog Abnormalities On Wildlife Refuges

Tuesday, November 19, 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 Tuesday in the peer-reviewed online journal PLOS ONE, finds that on average, less than two 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.

In 2000, Congress asked agencies within the Department of the Interior, including the Service and U.S. Geological Survey, to address growing concerns about the health of amphibians in the United States. In response, the Service launched a 10-year study, the largest ever of its kind, to determine the distribution and severity of amphibian abnormalities within the National Wildlife Refuge System. The research effort – called the National Abnormal Amphibian Program – sampled more than 68,000 frogs on 152 refuges, and in the process, compiled one of the world’s largest databases on amphibian abnormalities.

On average, only two percent of the frogs and toads were classified as having skeletal or eye abnormalities, the types of abnormalities most commonly studied. The expected background range of zero to two percent skeletal/eye abnormalities was found at many refuges. Extra limbs were exceedingly rare:  just 0.025 percent of all frogs sampled.

However, consistent with other, prior studies, the Service’s study detected areas where sites with higher rates of abnormalities tend to cluster together geographically. Within these regional hotspot clusters, which were found in the Mississippi River Valley (northeast Missouri, Arkansas and northern Louisiana), in the Central Valley of California, and in south-central and eastern Alaska, abnormality frequency often exceeded the national average of two percent, affecting up to 40 percent of emerging amphibians in some individual samples.

Analysis of the data showed that the location where the amphibians were collected was a better predictor of whether or not they would be abnormal than was their species or the year they were sampled. There was virtually no evidence that some species were more likely to be abnormal than others or that more abnormal frogs were found in some years than in others.  

Although this study was not designed to investigate the reasons behind amphibian abnormalities, the results strongly implicate localized causes. This is consistent with other research, some of which has identified contamination, predators, parasites or the interaction of these as potential factors.

The complete dataset from the study is being made available online at the Dryad Digital Repository (http://doi.org/10.5061/dryad.dc25r ) to facilitate future research to aid in the conservation of amphibians and their habitats. To view the journal article, visit http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0077467.

For more information on this study visit www.fws.gov/contaminants/Issues/Amphibians.cfm.


Blitz At Black Rock Mountain Will Boost Understanding Of Bats

The night life around Black Rock Mountain State Park will keep researchers from across the state busy Sept. 4-7. It is all part of the Georgia Bat Working Group’s first Bat Blitz. The event based at the park in northeast Georgia’s Rabun County is focused on better understanding the area’s bat communities. But there is an even bigger picture. Organizer Trina Morris ... (click for more)

Drones Banned From Appalachian Trail

The National Park Service has developed an interim policy prohibiting the use of unmanned aircraft on NPS managed lands of the Appalachian National Scenic Trail. This is a new park use that could affect park resources, staff, and visitors in ways that the National Park Service has yet to identify, analyze and examine. It is the National Park Service policy to not allow a new park ... (click for more)

Boy, 16, To Face Murder Charges In Criminal Court On Triple Lookout Valley Slayings

A Lookout Valley youth who was 15 at the time of his alleged involvement in a massacre in the valley will stand trial as an adult. Jacob Allison, who is now 16, was taken by the sheriff's office to the Hamilton County Jail after a transfer hearing in Juvenile Court on Friday morning. Juvenile Court Judge Rob Philyaw said under state law he has jurisdiction over rehabilitation ... (click for more)

Justin Wilkins Selected As Deputy Chief Of Staff For Mayor Berke

Native Chattanoogan Justin Wilkins will serve as Mayor Andy Berke's deputy chief of staff, it was announced Friday. Mr. Wilkins has spent the last several years serving as the Tennessee state director for multiple advocacy and electoral organizations, including Organizing for America and Organizing for Action. Prior to that, he worked as project manager at Profit Plans LLC ... (click for more)

Black Creek TIF Decision-Who Guards The Hen House? - And Response

Citizens of Chattanooga were invited to give public comment before their own Industrial Development Board Aug. 15. They arrived to find foxes guarding their hen house.  Many thought the meeting was their opportunity to seek redress in the ill-conceived Black Creek Tax Increment Financing plan. However, they learned it was a sham orchestrated by both the past and present ... (click for more)

Roy Exum: Let’s ‘Pay It Forward’

At 7 a.m. on Wednesday morning, this at a Starbucks coffee store located at 2186 Tyrone Blvd. in St. Petersburg, Fla.,  an unidentified woman who was first in line at the drive-through window, politely told the drive-through window clerk she would like to “pay it forward.” The clerk checked the next order – it was a caramel macchiato – and the first customer paid for both her ... (click for more)