A chilly, damp day in November 2009 marked a homecoming of sorts for about 500 northwestern frogs. These lucky amphibians were Oregon spotted frogs , many of which were raised behind the scenes at Woodland Park Zoo as part of an effort to restore the endangered species to its natural habitat in the Puget Sound region. They were released into Dailman Lake, which is located on the Fort Lewis Military Reservation in Pierce County.
Oregon spotted frogs are sturdy, handful-sized frogs named for the blotchy black spots that cover their olive green, brown, or red skins. But the species is not limited to Oregon. Populations of these frogs once inhabited shallow wetlands from southwestern British Columbia south through Washington and Oregon to northeastern California.
Today, however, the frog’s range is drastically reduced. In Washington State, remnant populations are found only in Klickitat and Thurston counties. About 20 populations remain in Oregon, and one in Canada.
The decline is primarily the result of loss of habitat due to the filling of wetlands for agricultural and construction purposes. Disease and predation by non-native introduced species, such as the American bullfrog and game fish, have also taken a toll on the frogs.
Conservation efforts to restore frogs and boost the numbers of wild populations include “headstarting” frogs in captivity. This process begins with the collection of fertilized frog eggs in the wild. The eggs subsequently hatch and tadpoles mature without any danger of becoming a meal for a hungry fish or bullfrog–a fate that usually claims up to 80 percent of juvenile frogs in the wild. Seven to nine months later, upon maturity, the frogs are released.
Some of the frogs released in November were implanted with tracking devices to aid in future studies. About a quarter of the frogs released into the Fort Lewis site carry microchips, which can be read using a wand, just like the identifying microchips embedded in many cats and dogs.
In 2008, about 600 frogs raised at Northwest Trek were released at the Fort Lewis site. 2009’s crop of hoppers were raised at Woodland Park Zoo and Oregon Zoo as well as the Cedar Creek Corrections Center, near Olympia, as part of an endeavor called the Sustainable Prisons Project run by The Evergreen State College and the Washington State Department of Corrections. Biologists from the Washington Department of Fish Wildlife, Oregon Zoo, and the U.S. Army were also involved in the release.
More releases are planned for the next three years. The frogs will be monitored during that time. In 2012, the project will be assessed to see if the population has become self-sustaining.
Why is so much effort being poured into the conservation of one frog species? How can a critter that weighs no more than three ounces command so much attention? The answer lies partly in the frog’s ties to other species in its habitat and the health of the habitat itself.
Like many other amphibians, the Oregon spotted frog is an “indicator” species for its habitat–in this case, shallow marshes with seasonally warm waters. Much of this habitat has been destroyed since Europeans first settled in the region. Species that are sensitive to disturbances in their habitat and depend mightily upon a particular habitat for survival (such as the Oregon spotted frog) are like the proverbial canaries in the coal mine whose distress signals trouble.
The presence of a healthy population of this native species of frog, on the other hand, indicates that surviving portions of their habitat are functioning well as ecosystems. The frogs also serve as food for many predators, such as herons and garter snakes. In addition, the existence of healthy frogs is a sign of good water quality–a boon to both wildlife and humans in the Puget Sound region.
Find out more: “A Conservation Assessment for the Oregon Spotted Frog (Rana pretiosa)” provide an in-depth look at the ongoing effort to conserve the Oregon spotted frog and its habitat.