The research, described in the December issue of Conservation Biology, shows that while amphibian malformations and the parasitic worm that causes them have been found in lakes and ponds for more than 50 years, they have substantially increased in their abundance during this period.
Pieter Johnson, a University of Wisconsin-Madison graduate student in zoology and lead author of the recent paper, says that frog deformities have been a hot topic since the mid-1990s, when the abnormalities began to be widely observed. To date, severely malformed frogs, toads and salamanders have been found among 60 different species in nearly all U.S. states, as well as parts of Canada, Japan and several European countries.
The high number of amphibian deformities, explains Johnson, is of great ecological concern. Severe limb deformities cripple amphibians, making it difficult for them to catch food or escape predators. "We know that most malformed frogs die before sexual maturity," says Johnson, adding that these malformations, coupled with other factors, could threaten entire populations of amphibians.
Keeping amphibians in lakes, ponds and other wetland environments is important for a number of reasons, explains Johnson. These organisms are integral to the food web - they gobble up a large number of insects and aquatic plants, and snakes, fish and birds eat them. They also serve as an indicator species - organisms scientists say can signal subtle changes in the environment.
"There's the personal appeal, too. Kids have always been fascinated with frogs," says Johnson.
Although sightings of deformed frogs are more common today, they have been reported by scientists,
Contact: Pieter Johnson
University of Wisconsin-Madison