"When simple tests of species physiology are interpreted outside of the animal's natural environment, we often come to the wrong conclusions," Palen says.
For one thing there are lots of "natural sunscreens" in the water. They are in the form of dissolved organic matter remnants of leaves and other matter from wetlands and terrestrial areas that are dissolved in the water, much like tea dissolved in a mug of water. The more dissolved organic matter, the less UV exposure.
And places where the water is more crystal clear, the females from the susceptible salamander behaved differently.
"There hasn't been a lot of work on whether organisms are capable of sensing UV intensity, but these salamanders certainly do," Schindler says. "They change their behavior, with the females laying their eggs in the shade when the clarity of the water puts their eggs at risk."
If for some reason UV radiation were to become much more intense, it could reach a point where amphibians can't behave in ways that protect them, Palen says. But the restrictions on the use of ozone-depleting chemicals, under what's called the Montreal Protocol, appear to be helping restore the ozone layer, which filters the amount of UV radiation reaching Earth.
"By critically evaluating what appear to be threats to ecosystems, we can refine our research and conservation priorities and move onto those that will make a difference in helping amphibians survive," Palen says.
The study area includes one of the richest amphibian habitats in northwest Washington's Olympic National Park. The work was conducted in the Seven Lakes Basin of the Sol Duc drainage in subalpine terrain, that is, on mountain sides just at the point trees struggle to grow.
Palen and Schindler intentiona
|Contact: Sandra Hines|
University of Washington