Frog Die-offs at Acadia Examined
Scientists searching for answers to plight of park's species.
ACADIA N.P., MAINE-A major three-year study under way at Acadia National Park seeks to solve the mystery of what has been killing the young age classes of four frog species in the park.
Scientists at the National Wildlife Health Center have diagnosed several diseases after dissecting specimens of frog species that have been dying off in the last four years at park wetlands. These diseases, including a fungus, viruses, and protozoans, have caused complete or high mortality rates for wood frogs, green frogs, bullfrogs, and spring peepers. Park staff and scientists hope to learn whether these die-offs are natural occurrences or the result of a combination of environmental changes, such as air and water pollution, ultraviolet radiation, or toxins.
"The preliminary investigations have documented diseases at some wetland sites," said Bruce Connery, a park biologist. "Current information suggests that younger-aged groups of frogs are more susceptible, perhaps because of their less developed immune systems at specific stages of development.
"It is unclear whether shifts in environmental conditions could create additional physiological stresses for these young frogs," he added.
A full research effort began this spring. Researchers are tracking day-to-day environmental conditions and the development of frogs at various park wetland sites, hoping to detect the onset of disease.
Among the questions being asked is whether the diseases will go away on their own in a year or two-allowing the species to recover-or spread elsewhere. Scientists also hope to learn whether the disease can spread via researchers' boots or on birds or ducks. Ultimately, the plan is to reproduce in healthy frogs the diseases affecting the Acadia frogs, to learn more about how the diseases begin and progress.
"The more events we look at and the more opportunities we have to examine healthy [frog] populations, the greater the chance that we'll be able to put together the pieces of the puzzle," Dr. David Green, a veterinarian who is also working closely with the park study, told the Associated Press.
Scientists investigating the dynamics of Acadia's wetlands first reported the die-offs of young frogs, which coincided with reports of declining frog populations or high occurrences of malformed frogs from 42 states. Connery said that the study coincides with similar research efforts under way in the Appalachian mountain states and the West.
Researchers are unsure of the direction the Acadia study will take in year two, but they are confident that it will yield results. "If nothing else, it will answer some questions and point us toward areas of other research," said Connery.
"The days of us expecting to find one root cause are long past," he added. "We're looking at a complex situation with many events and factors that may have been there all along but is now pushing the [frogs'] stress levels or immune systems to the breaking point."
