Frogs versus toads
August 1, 2009
By Christopher Huber
New, August 1, 1:50 p.m.
Experts say the native amphibian populations in Sammamish are threatened and more vulnerable than ever due to predation, more competition for food and urbanization which leads to loss of shelter. Their plight has potentially serious implications for the local food chain and ecosystem overall, said Klaus Richter, a frog expert.
For years during the 1980s and 1990s, Richter studied native amphibian habitats and populations on the Sammamish Plateau. Back then, he and fellow researchers found healthy western toad populations around Beaver and Pine lakes. That was before Sammamish was a city and before much of today’s development happened.
It’s been a while since Richter, a senior ecologist with the King County Department of Natural Resources and Parks, did formal frog research in Sammamish. However, he said he has not come across western toads in the past several years. He knows things have changed for the native populations here with expanding development and the introduction of non-native bullfrogs. Both of these factors are stressing the native population of frogs.
The role frogs play makes them a bellweather for the local environment as a whole.
“Frogs are bio-indicators, so we can judge the health of the ecosystem based on the health of the frogs,” said Dr. Kerry Kriger, frog expert and founder of Save the Frogs.
This isn’t unique to Sammamish, but native frogs and toads are stressed in their habitat here, the researchers said.
“If you’re stressed, you’re more vulnerable to predation,” Richter said. “They’re being stressed to a greater extent than they used to.”
And as the toads go away, the mosquitoes and ticks have fewer predators.
“The key thing that people should understand is, they do a lot of insect control,” said Amy Yahnke a University of Washington graduate student. She and Krieger recently came to a Sammamish wetland to do research on local frogs.
“These are little bio controls for all the bugs we don’t want bugging us,” Yahnke said. They have a huge predator biomass, which means they can eat a lot of bugs.”
Parts of the problem
Bullfrogs are considered an invasive species that threaten the toads and other native species. If bullfrogs become the lone species on the plateau, residents lose the year-round pest control.
It’s important to maintain a balance in the various frog species populations on the plateau because different frogs are active during different times throughout the year, Kriger and Yahnke said.
“The key to this is that each of the native species we have fills a niche. They breed and go through their life stages at different times in the year,” Yahnke said.
Bullfrogs, she said, are only active when it’s warm. As a result, there would be few frogs controlling bug populations, and acting as food for larger animals, from January to June.
“The Sammamish Plateau is a good example of threatened frog populations because it is an area that is part of the historic range of Oregon spotted frogs, a candidate for listing under the Endangered Species Act, and where western toads, a Washington state Species of Concern, have been recently documented,” Yahnke said.
As bullfrogs edge out local species, they become a “bio-pollutant,” which Richter equated to a beer can having babies. You can pick up littered beer cans, thus fixing the garbage problem. But that’s not the case with animals.
“Western Toads have undergone serious decline throughout their range due to habitat destruction, invasive bull frogs (which were at the site) and the chytrid fungus, which causes a potentially lethal skin disease that has driven nearly 100 amphibian species to complete extinction worldwide,” Kriger said.
Nearly one-third of the world’s 6,485 amphibian species are threatened with extinction, according to Save the Frogs. And in recent decades, about 150 species have gone extinct.
“Ten percent of the Nobel Prizes in physiology and medicine have come from research that depended on frogs,” Kriger said.
According to Save the Frogs, the amphibians produce a variety of skin secretions, many of which can potentially to improve human health through pharmaceuticals.
How to help
Klaus Richter, a frog expert with King County, said one misconception people have about frogs is that they hang around the pond their entire life.
With the exception of bullfrogs, however, frogs spend most of their life in the woods, taking only a few weeks in the spring to breed near the water.
“We have a wrong idea, a misinterpretation, of what they need to stay and to live long,” Richter said.
Native frogs need larger buffer zones around area wetlands than currently exist, whereas bullfrogs tend to stay near the water, Richter said.
A simple way to help them, said Amy Yahnke a graduate student researching frogs, is to provide a corridor of cover.
“Plant some ferns and shrubs and give them a place to hide,” she said. “But generally, if we can decrease the vast expanse of lawn that they have to cross by planting a few pretty things to give them a leg up across the yard, it would help.”
She also suggested rain gardens might help the frogs find cover and reduce changes ot the water level in nearby wetlands.
Yahnke also advised curious residents to appreciate frogs where they are, rather than adopting the cute amphibians into the house, keeping them in a cage or aquarium — they eat a lot more bugs if they’re outside.
Learn more about frogs around the world at www.savethefrogs.com.
Six factors affecting native frogs
- Habitat destruction (development)
- Infectious diseases (chytrid fungus)
- Pollution and pesticides
- Climate change
- Invasive species (bullfrogs)
- Over-harvesting (for pet and food trades)
Reporter Christopher Huber can be reached at 392-6434, ext. 242, or firstname.lastname@example.org.