Frogs, toads, salamanders, newts and caecilians (tropical species resembling worms) all are considered amphibians. The term means "dual life," a phrase that refers to the fact that amphibian species live their lives both in water and on land. Amphibians are the Earth's oldest group of terrestrial vertebrates and have amazingly diverse life cycles and habitat requirements. The one thing they have in common, especially in North America, is a need for aquatic habitats such as wetlands.

Wetlands of all sizes filter and protect drinking water, sustain plant and animal biodiversity, help to prevent downstream flooding, and prevent erosion. Many amphibian species thrive in shallow ponds the size of a football field -- so long as they are uninhabited by fish that prey on their larvae.

Some need little more than a ten-foot mushy spot in low-lying woods in which to lay their eggs. Others may spend just a week or two in a wet depression before crawling some distance upland to seek refuge in the leaf litter and crannies of the forest floor.

"What we hadn't realized up until five or six years ago is that, in fact, these small, unnoticed wetlands are very important for amphibians because they are ephemeral, which means they dry out periodically and eliminate predators, such as fish." The amphibian world needs these small, scattered wetlands that usually dry up for part of the year just as much as flocks of migrating ducks and shorebirds need expansive tracts of permanent, shallow wetlands.

Semlitsch and his students began focusing research questions on these ephemeral types of wetland habitats, looking into how amphibians go about living and reproducing in such places. They are currently studying how amphibian offspring disperse themselves among different wetlands, and how they make use of the land around the watery places. This differs from traditional approaches to amphibian research which concentrate mainly on local populations that are tied to one particular wetlands breeding area.

Semlitsch has looked beyond these to a larger landscape, bringing into his research whole groups of populations that are referred to as "metapopulations." He developed this approach through personal experience.

Semlitsch began his research career in an area of South Carolina that boasts one of the highest amphibian species diversities in North America. The "Carolina bays," where Semlitsch first put on waders, are composed of rare 5,000- to 50,000-year-old wetlands that remain almost untouched natural places. From there he traveled to Switzerland to teach at the University of Zurich. "I started working in Europe, and there I really saw the dilemma that most of the world's biodiversity faces," Semlitsch says. "Humans have dominated the landscape in Europe, of course, for centuries, and there's not a square inch that hasn't been destroyed, rebuilt or restored. I had just come from South Carolina and I was spoiled, in a sense. I was faced with these two contrasting pictures, and I became convinced that amphibians were suffering from the same problems as other taxa."

He turned his attention away from studying basic ecology and behavior of amphibians to more specific, applied-science questions: "The neat thing is that my background was so strong in natural population dynamics in pristine habitats. So I knew what it took for amphibians to persist in undisturbed habitats. What we had to do was begin to ask questions about what they are doing [in pristine places] that they can't do in disturbed habitats."

At MU, Semlitsch and his students have plunged into this question. So far, their findings suggest that if the overall density of small wetlands is reduced, then wetlands animals will have to travel farther to find mates and new breeding grounds. Animals in such situations often become genetically isolated, which leaves them susceptible to inbreeding and the reproductive problems this implies. This results in species vulnerable to extirpation -- disappearing -- in that particular spot.

"Once we knew what they do in controlled conditions," explains Semlitsch, "we could pursue studies of what happens to amphibians when we cut the forest, or when they encounter a pasture or type of road. A dirt road may not be an obstacle, but what happens when it's a paved road? Or a flat road may not hinder their movement, but what happens when you put a curved crown on that road? Will they go up that slope or over a curb?"