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Ponds built in Iowa for sagging frog population

By Staff | May 28, 2010

CEDAR RAPIDS (AP) – Kermit the Frog would be pleased by all the pond-building at the Indian Creek Nature Center in the last two years.

The ponds built in the Cedar River flood plain are meant as new homes for the area’s sagging frog population.

Frogs have suffered from the dramatic loss of ”ephemeral ponds,” Indian Creek Nature Center Director Rich Patterson said. The term refers to ponds that fill up in early spring with snow melt and rain and then disappear in the heat and dryer months of summer.

Thousands of ephemeral ponds once lined the Cedar River valley, Patterson said, a natural result of scouring and sedimentation during floods. Most of them were filled and flattened after the area was settled to create more usable farmland and lawns.

Ephemeral ponds provide relative safety for frog reproduction that year-around ponds and rivers don’t, Patterson said. Without fish and other large species, the eggs laid by frogs and the tadpoles that hatch from them have a better chance of maturing.

The Indian Creek Nature Center has built many ephemeral ponds over the years. It added one last year and another smaller pond this year.

The project got a huge boost last year when the Cedar Rapids Water Pollution Control Division re-lined a crumbling sewer interceptor that runs underneath property the center leases from the city.

The city and the nature center knew the interceptor work would be disruptive to wildlife habitat in the area, and the city agreed to Patterson’s suggestion for offsetting the temporary damage by building ephemeral ponds.

A roughly 1.5-acre pond was built by the city near the Cedar River, not far from the wastewater treatment plant. Patterson said the pond has filled with water this spring and become a breeding ground for many frogs and other species.

”It is very, very progressive to include ephemeral ponds in a wastewater treatment project,” Patterson said.

The pond is linked to the Cedar River by a culvert and has a small island for waterfowl habitat.

The pond is much closer to the Southeast Wastewater Treatment Plant than to the Indian Creek Nature Center, so it’s unlikely to be visited often. Because it’s only 2 or 3 feet deep, it will be empty most of the year.

Several ephemeral ponds near the nature center, including one with a boardwalk, are visited frequently.

Program specialist Margaret Wolter conducts frog walks at the nature center, where the mating sounds of peepers, chorus frogs and others provide evidence of spring.

Frogs and toads are generally in decline across Iowa because of dwindling habitat and other factors, Wolter said. Tracking the frog and toad populations provides an indication of the health of local ecosystems, because of their sensitivity to certain pesticides and other threats.

The Iowa Department of Natural Resources has been organizing a frog and toad call survey for about 20 years in Iowa. The differing mating calls of frogs in breeding seasons is a much easier way to track their presence than visual identification.

Stephanie Shepard of the DNR’s Wildlife Diversity program says the state has no data on declining frog habitat, adding that it ”would probably be depressing” if the statistics were known. The DNR’s last survey covered 292 sites, with chorus frogs and cricket frogs being the most-heard varieties. American toad reports were down last year, allowing the Eastern gray frog to move into third place.

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