Amphibian abnormalities have been addressed in scientific literature for some time, but it was only when middle school students in Minnesota discovered large numbers of abnormal frogs that the general public and Congress began to notice. That was in 1995 and researchers have been investigating the problem at many levels ever since – including research on national wildlife refuges.

Environmental stressors may cause abnormalities such as missing, extra or unusual body parts. In fact, scientists believe amphibean abnormalities could be caused by multiple factors that may differ from one site to another. These factors may include changes in climate, predators, parasites, bacteria, fungi and viruses or pollution and contaminants such as pesticides, metals and fertilizer, among others.

The Service launched a nation-wide scientific survey to determine the extent of abnormal frogs and toads on national wildlife refuges in 2000. With the help of refuge staff, volunteers, Friends organizations and at least one student group, simple first-tier assessments of frog and toad abnormalities have been conducted in ponds, wetlands, puddles, and other water bodies on more than 152 refuges in 45 states. This effort represents the first nationwide survey of abnormal amphibians that uses standardized collection and evaluation methods.

During the initial assessment, researchers tried to collect 50-100 newly metamorphosed frogs of one species from a single pond and document visible abnormalities. Abnormal frogs were sent to a parasitologist who looked for parasites that cause abnormal limb development. Then the frogs were sent for radiography so that any bone abnormalities could be examined and documented.

The Service has analyzed 10 years of data and has presented our findings in a recently released publication in the online journal, PLOS ONE.

Standard Operating Procedures (SOPs)

Standard Operating Procedures (SOPs) used by our National Abnormal Amphibian Program are available online at the Dryad Digital Repository along with the complete dataset used in our recent PLOS ONE publication.

Last updated: November 15, 2013