Counting Croaks and Ribbets / Volunteers moniter frog population

Counting Croaks and Ribbets / Volunteers moniter frog population

2000-04-21 04:00:00 PDT ALBANY -- One night a week, Margaret Hurlbert hikes out to a pond near the Union Pacific railroad tracks in Albany. She sits down, and for three minutes, she listens.

She hears freeway noise, trains roaring by, the occasional car horn, and then, suddenly, "ribbet."

It is a Pacific tree frog. Not bad, but she was hoping for the muffled, whiny croak of the endangered red-legged variety.

"I'm still hunting. I still think it may be here," she said. "If you stick around long enough, you're bound to hear it eventually."

She goes back home and records the time, date, location and weather conditions and sends the information to Frogwatch, a nationwide volunteer organization that is attempting to monitor the country's declining frog population.

"It's wonderful to sit under the stars and just listen for frogs," said Hurlbert, who works in the pest control department at the University of California at Berkeley. "It's very relaxing. Better than TV. I highly recommend it."

The croaks and ribbets of mating frogs, once a staple of springtime, are now almost silenced. Frog populations around the world plunged 15 percent a year every year from 1960 to 1966 and have dropped about 2 percent a year since then, according to a study published in a recent issue of the journal Nature.

Scientists are not sure why, but theories include habitat loss from development, pesticides in the air and water, disease, global warming and an invasion of bullfrogs, which eat other frogs.

Frogwatch, a pilot program of the U.S. Geological Survey, is an attempt to help scientists solve the mystery of vanishing amphibians. By studying the data, researchers can track different species and their breeding patterns and get a better picture of overall trends in the frog population.

Frogwatch is not a foolproof system, but it is a leap in the right direction, said Gideon Lachman, Frogwatch coordinator.

"It's good to go out and get as much information as we can and see what's going on," he said. "If we wait for scientific studies, it could be too late."

Frogwatch is run on a shoestring budget with a three-year, $8,000-a- year grant that expires in 2001. With no money to advertise, Lachman relies on the Internet and word of mouth to recruit volunteers. So far, Frogwatch volunteers are monitoring 650 different vernal pools, streams and ponds in 48 states.

While the data is useful for scientists, Frogwatch also has a promotional mission: It gets the public attuned to the wet and swampy world of frogs -- what different species sound like, where they live, when they mate and how to protect them.

"What we've learned is that we have frogs that live around here and their habitat is worth saving, worth protecting and even enhancing," said frog-watcher Susan Schwartz of Berkeley. "We're making signs to put up around town that say, 'This isn't just a puddle, it's a frog habitat.' "

Even in urban areas, frogs can breed and thrive under the right conditions. In the East Bay, frogs are alive and croaking at the BART right of way in El Cerrito, the reflecting pools at Blake House in Kensington, soccer fields and other marshy spots.

Frogwatch has few participants in other parts of the Bay Area, but West Marin, the Peninsula Open Space District and Golden Gate Park are likely habitats for local amphibians.

"Anyplace with ponds, you're going to have frogs," said Schwartz.

Frogs used to be abundant in the Bay Area. Red-legged and Pacific chorus frogs once filled ponds, puddles and streams. Now, the Pacific chorus frog is rare, and the red- legged frog is on the state and federal endangered species lists.

In the Sierra Nevada, frogs are nearly extinct.

"I remember when I was doing field research in the '60s, you could go to a pond and see hundreds of yellow-legged frogs. Now, there are none," said Gary Fellers, a research biologist studying frogs for the geological survey at Point Reyes National Seashore.

"We've already lost more than half of certain species in the Sierra over the last 12 to 14 years, and some species are completely gone from whole watersheds," he said.

Fellers suspects that pesticides and herbicides drifting up from the Central Valley are responsible for the decline. Thousands of tons of chemicals are applied to crops there every year, and agricultural practices changed about the same time the frog population started dropping, he said.

"Frogs have permeable moist skin. They live in land and water, and they eat insects," he said. "These guys are sampling quite a large range of the habitat, so they're especially vulnerable."

Frogs do not have the political cachet of spotted owls or bald eagles, but their decline is still reason for alarm, Fellers said.

Aside from frogs' role in the food chain and the sentimental appeal of their ribbets and croaks, frogs are a good indicator of the overall health of the environment.

Frogwatch coordinator Lachman called them "canaries in the coal mine."

"If there are contaminants at high enough levels to kill off vertebrae like frogs, they're probably at significant levels to affect people," Fellers said. "Obviously, people who vacation or live in Yosemite aren't dying overnight, but it could be slow, over a period of time. It could be sublethal. That's something we need to study."

Fellers and other scientists hope eventually to pinpoint the exact cause of the amphibian decline and take steps to protect the creatures. In the Bay Area, Frogwatch volunteers have already taken matters into their own hands.

Jim McKissock of El Cerrito recruited three classes of sixth-graders from Sierra Prospect School to help him remove wood chips from a pond where frogs breed.

"We ended up with thousands of pollywogs there. It was like a miracle. We've never had this many pollywogs there," he said. "It was really satisfying for all of us. But it's a constant battle to save these habitats."

McKissock, who grew up in nearby Richmond Annex, remembers when vernal pools appeared every spring in vacant lots, and "at night the whole place was like a chorus of frogs. There were millions of them."

"I told the kids, you may be the last kids to see frogs unless we do something," he said. "They were excited to help."

In Marin, Ro LoBianco became so enamored of the frogs, egrets, geese, mice and mallards in the Strawberry Point marsh he was monitoring that he has become a vociferous opponent of development there.

The Mill Valley School District wants to drain part of the marsh for a ball field and a parking lot as it reopens Strawberry Point School.

"We're losing so many wetlands on the Tiburon peninsula," he said. "When people think of saving wildlife, they think of bigger animals like deer. They don't think of amphibians. But we have to protect them, too."

Frog-watching will continue through the end of the month. For more information, call the Frogwatch headquarters at (301) 497-5819 or go to the Web site,

www.mp2-pwrc.usgs.gov/FrogWatch/index.htm.