Frog Man : A Young California Scientist Goes Pond-Hopping to Find Out Why Our Amphibians Are Dying Off

THE SKY IS NOT yet black, but already small bats dart about in the humid air above a murky, isolated pond. A high-pitched symphony of chirping crickets, eerie background music suitable for a “Twilight Zone” episode, is broken by the buzz of a bloodthirsty mosquito as it hovers at ear level. The ear is mine, and, within minutes, the mosquito bites will be mine, too.

On this summer evening, one of the hottest in Southern California history, I am watching five grown men relive their boyhoods at the pond’s edge. Every few minutes, someone focuses his flashlight on a spot, smacks his hand down on the water and raises a squirming frog in triumph. “Here’s another one!” a man shouts from the far end of the pond.

The members of this expedition have journeyed to a nature preserve in the southwest corner of Riverside County to hunt California red-legged frogs. Some of the men are longtime friends; others are new acquaintances. But they all share a passionate interest in one of the oldest classes of creatures on Earth, and their mission tonight is to conduct part of a census of frogs that may face extinction.

Leading the group is Mark Jennings, a tall, sandy-haired, mustachioed naturalist in waders and a wide-brimmed felt hat. As his buddies grab frogs from the pond, he lays his bulky day pack in a dry spot a few feet up the bank and pulls out a handful of plastic freezer bags to hold the frogs. All the while, Jennings calmly offers instructions: “Try to clean the pond out... Once you get everybody, then you can let them go again.”

Then he wades into the thigh-high water himself, scanning the edges of the pond with a miner’s lamp he holds at eye level. Small, jewel-like eyes flash under the light. It’s one of the muddy, green red-leggeds, now sitting placidly in shallow water.

When it comes to California red-leggeds, Jennings is an expert. At 34, he is an ichthyologist and herpetologist who holds a doctorate in wildlife and fisheries science from the University of Arizona. But in recent years, he has been less concerned with fish than with amphibians, and he has visited virtually every spot in the state where red-legged frogs are known to live. He has tracked them, counted them, published papers and lectured about them.

Jennings counts himself among a growing number of scientists who in the past decade have noticed dramatic, sometimes sudden decreases in the worldwide population of frogs, toads and salamanders. Declines have been documented in dozens of species in at least 16 countries. In Australia, for instance, there has been a serious drop in at least 10% of that country’s 194 frog species, one specialist in amphibians estimates. And at least two frog species in that country, including one novel creature that bore its young through regurgitation, are thought to have disappeared entirely.

In Southern California, many areas, including undeveloped canyons and mountains, that once teemed with tadpoles and several frog species now have few or none. If you can still find a frog in your back yard, it’s probably the ubiquitous bullfrog or tree frog. The days of easily finding something other than those two species are over.

Sometimes the reasons for the declines here and around the world are clear and simple. Wetlands have been drained for housing projects; forests have been destroyed by logging; tadpole-eating trout have been introduced into ponds and streams, droughts have dried up water holes. Other culprits include pesticides, acid rain and air pollution. But for every drop in the frog population identified and explained, the disappearance of another species in some apparently pristine wilderness remains a confounding mystery.

“There are so many variables, I think it’s really tough to say ‘OK, the decline is keyed to this particular phenomenon,” says Mike Hamilton, a UC Riverside ecologist and director of the university’s James San Jacinto Mountains Reserve study center near Idyllwild. “Very few things in nature are cause and effect. Almost every ecological relationship is so multivariate that it’s hard to pin it down to ‘this has an effect on that.”

In the grand scheme of things, many other animal species are disappearing as humans encroach on wildlife habitats. But the decreases in the amphibian population are so sudden and inexplicable that many herpetologists believe that frogs, toads and salamanders may have become like the proverbial miner’s canary. The declines, scientists say, could be a sign that environmental degradation has slipped from problem to crisis.

“If you lose these things, it’s really telling you that something’s wrong,” Jennings says. Amphibians’ smooth, porous skin and the fact that they live part of their life in water and part on land may make them more vulnerable than other animals to environmental pollutants and changes. Moreover, their place in the ecosystem, as insect predator and bird and mammal prey, make them especially important to its smooth operation.

“In some places, they’re real important. If you pull them out, all the other animals that depend on them are going to have to go to something else, if they can. If they can’t, they’re going to disappear as well,” Jennings says. Frogs, for instance, represent a particularly efficient way for nature to turn tiny, hard-to-catch protein sources, such as insects, into one juicy, edible steak for animals such as raccoons and snakes.

In February, the National Research Council hosted a meeting in Irvine to consider the worldwide amphibian decline. With Jennings and about 40 researchers who study amphibians on several continents in attendance, the conference marked the first time scientists had addressed the problem in an organized fashion and thought about how to collect more solid data to determine its extent and its causes. A Canadian scientist complained of no longer being able to find tadpoles in certain spots in Nova Scotia. Other scientists told how some tropical frogs have dropped from thousands in number to a handful during the past decade. Before the meeting’s end, though, all the scientists agreed that many of the most dramatic and mysterious disappearances are taking place in the mountains of the western United States.

THE CALIFORNIA RED-LEGGEDS Jennings and his friends are hunting this evening are on a 3,100-acre preserve owned by The Nature Conservancy, a national nonprofit environmental organization. The preserve--a mix of grasslands, oak groves and creek beds--overlooks a valley of new housing tracts and shopping centers. These days, California red-leggeds are rare here. As far as anyone knows, this population, which numbers no more than 100 frogs at any one time, is the last one south of Ventura County.

Jennings began monitoring these red-leggeds last year. Now he has returned for his first visit to track their decline or, he hopes, their rebound.

After 20 minutes, Jennings and the four other men have as many frogs as they think they will find on this outing. Plastic bags containing frogs sit--and occasionally hop--on the bank. Some of the bags are smeared inside with a frothy liquid produced by the frogs. “That’s supposedly a defensive posture,” Jennings explains. “If something grabs it, like a raccoon or something, then the frog can slip out.”

Jennings sits down next to the frogs and removes equipment from his pack. He distributes a small scale for weighing the frogs, a plastic ruler for measuring their length and a pair of sharp surgical scissors for snipping off a toe or two to mark them. For the next half-hour, the men carefully pull one frog at a time from the bags, take measurements and read them to Jennings. He jots down everything in a small, red notebook he keeps for field notes and data.

Last year, three ponds on this preserve, each barely the size of a backyard swimming pool and only half as deep, contained red-legged frogs. Then a volunteer at the preserve discovered that a pregnant bullfrog--a voracious, non-native species blamed for wiping out many indigenous frog populations--had found its way into one of the ponds. The bullfrog and its offspring apparently feasted on the red-leggeds before volunteers and preserve manager Gary Bell removed and destroyed the intruders. This year, only two of the ponds have California red-leggeds.

Jennings speculates that in some cases, the state’s red-leggeds may have been hunted so heavily that they were unable to re-establish their numbers. In other cases, trout introduced to lakes and streams may have taken their toll. Then, as floods and rains wiped out one weak population, there were too few frogs left to re-colonize. In addition, much of the red-leggeds’ habitat has been destroyed, replaced by parking lots and housing tracts.

Long ago, even before the conference in Irvine, Jennings knew there was a problem. He has studied California frogs and their waning numbers, sometimes on assignment for government agencies, sometimes on his own for the past decade. His professional interest began shortly after he received his master’s degree in natural resources at Humboldt State University. He decided to conduct a study of his own on native California frogs. “I was taking some life history information, setting up study sites. I found it was real tough to set up sites because animals were gone from so many areas.” Soon he turned his attention from the simple question of how the animals live to the more complex one of why they are dying off.

While growing up in Santa Paula, Jennings was curious about insects, lizards, snakes, tortoises, frogs and just about anything else that lives at ground level. He remembers catching his first frog during a visit to the Kern River when he was about 4. He held the frog in a jar on his lap during the entire drive home, elated about his new pet. Now, as a scientist based in Davis, he is still particularly fond of frogs. They are easy to handle and breed for study, he says. But they are also just plain cute and fascinating to observe in their natural habitat, he adds.

In 1988, Jennings and another herpetologist and frequent collaborator, Marc Hayes, won a three-year contract from the California Department of Fish and Game through the California Academy of Sciences, which operates Golden Gate Park’s natural science museum complex in San Francisco. The goal is to survey the state’s reptile and amphibian population and to identify which animals deserve special protection as a declining, threatened or endangered species.

The pay is so low--a total of $15,000 for both men--that Jennings says it doesn’t quite cover their travel and other expenses. But the project is a labor of love. In the spring, when Jennings’ boss at the U.S. Fish and Wildlife Service in Dixon, near Sacramento, told him that the amphibian census was conflicting with his work studying fish and toxins, Jennings chose to leave the agency rather than give up the frogs.

Before Jennings and Hayes began their study two years ago, the state knew that there were 47 amphibian species in California, 12 of which are frogs and 11 of which are toads. (A toad generally has rougher skin than a frog and poison glands behind its eyes.) Over the years, seven salamanders and one toad had been identified by the state or federal government as threatened or endangered. But no one had conducted a comprehensive survey to determine which other species might be eligible for protected status. Such protection means hunters and fishermen are prohibited from capturing the creatures, collectors can rarely own them and developers must prove that any proposed construction that encroaches on a habitat will not annihilate them.

To begin their work, Jennings and Hayes asked other herpetologists and field biologists for information about which amphibians seemed to be plentiful and which seemed to be rare or threatened. The most helpful sources were the scientists who kept careful field notes--old-time naturalists who spent lots of time outdoors, watching and recording everything around them. Today, Jennings says, fewer and fewer biologists get out in the field. The technology of science, the ability to look at everything at its most basic molecular level, has tended to tie animal biologists to their lab benches. When they do get out, they are not trained to take precise notes of all they see. If they do record their observations, it is often into a tape recorder, and the cassettes rarely get transcribed.

After consulting their colleagues, Jennings and Hayes whittled their list to fewer than a dozen amphibians that might warrant protection. Then, as often as they can, Jennings and Hayes--known as the Marx brothers in herpetology circles--travel to out-of-the-way locations where historical records and other biologists’ old field notes indicate the amphibians have been seen.

So far, they have confirmed suspicions that the California frogs faring the worst are members of the genus Rana , a group that is distinguished by its long legs and a set of glandular ridges that run along each side of the body. Depending on habitat, climate and food sources, the life cycle of these frogs--from egg to adult--can range from one year to seven. Scientists are uncertain how long these frogs live once they mature. The genus includes the mountain yellow-legged frog, the foothill yellow-legged frog, the lowland leopard frog, the northern red-legged frog, the spotted frog--and the California red-legged frog.

As frogs go, the red-legged is more famous than most. Based on his research of historical records, Jennings is convinced that the pear-sized animal is the legendary jumping frog of Calaveras County whose hopping prowess was sabotaged by a gut-load of quail shot in the famous Mark Twain tale. “It’s a part of our history, a part of our culture,” he says. “To lose that animal would be, in a sense, to lose part of our folklore.”

Red-leggeds were once one of the most common of California frogs, found all over the state and hunted during the post-Gold Rush years for their meaty red thighs. Today, they aren’t even found in Calaveras County. They are still abundant, though, in coastal areas from Point Conception to Point Reyes, where fresh-water wetlands shaded by trees and reeds remain.

After a sweltering night at the Riverside County nature preserve, Jennings records only 16 frogs in his notebook. That’s about half the number he found last year.

“It’s too late for the red-legged frogs in Southern California,” he says gloomily. “Maybe we’ll get lucky and see something elsewhere, but, I mean, (this) population is on its way out.”

THE NEXT DAY IS ANOTHER hot one, and Jennings and Patrick McMonagle, a substitute teacher and a graduate student in biology from the San Fernando Valley, are hiking uphill along a palm-lined stream on the eastern edge of Palm Springs. They keep their eyes on the water, watching for tadpoles and frogs. I keep my eyes on them, hoping I won’t get lost in this outdoor oven with my single quart of purified water.

Jennings has heard that mountain yellow-legged frogs recently have been spotted in this area. During the past two decades, this species has virtually disappeared from Southern California, even from pockets in relatively isolated regions of the San Gabriel Mountains. Now, their numbers are also down in historic strongholds in the high elevations of the Sierra.

David Bradford, a UCLA environmental biologist, has collected data showing that in the past decade these frogs have disappeared from about 50 high-elevation lakes and ponds where they have historically lived. Last September, he visited a pond in the Convict Creek basin in the Inyo National Forest that was full of tadpoles. When he revisited the site in the spring, there was no sign of mountain yellow-leggeds.

“Sometime between last September and the spring melt, all these guys died off, and that’s pretty shocking,” Bradford says. Researchers have found in the Rocky Mountains and in parts of the northeast that acid rain and acid snowmelt have caused some amphibians there to disappear. If the water in which the frogs, toads and salamanders lay their eggs becomes too acidic, the embryo will either die or the tadpole that evolves will be defective. Bradford has been studying acid precipitation in the Sierra under a grant from the state Air Resources Board, he says, but it is too early in the study for him to draw conclusions about acidity levels and frog populations there.

Some amphibian specialists, including Jennings and Hayes, suspect another hard-to-prove environmental factor may play a part in the demise of the mountain-dwelling frogs. They theorize that increases in ultraviolet radiation, created by the slowly eroding ozone layer, may be killing frog eggs and adult frogs at higher elevations. And because of their thin skins, the frogs may be particularly sensitive to ultraviolet rays.

So far, one study has shown that artificial increases in exposure can impair tadpole development in a lab setting. Next spring, Hayes intends to help conduct a study to determine whether ultraviolet radiation is hurting mountain-dwelling frogs in their natural habitat. That project will be independent of the state amphibian census, but it may help scientists add or exclude one more explanation for the California disappearances.

Now, though, as we weave across the desert stream, it occurs to me that nothing in its right mind, not even a frog, should be running around in this inhospitable climate. I see Jennings upstream, staring intently into the water. His face is flushed from the heat. In a minute, he signals that he sees something. From 10 feet away, he has glimpsed a tiny tadpole lingering near a rock on the far bank.

McMonagle and I join Jennings, and we all stare at the tadpole, speculating about what kind it may be. McMonagle, a husky teddy bear of a man, dips a sandwich bag in the water and begins to coax the tadpole toward it with his hand. A short game of hide-and-seek ensues, and then the tadpole darts into the bag.

The tadpole’s body is about the size of a corn kernel. Its tail is clear, and its eyes protrude from the sides of its head. “Looks like a tree frog,” Jennings says. The eyes of a mountain yellow-legged tadpole would sit higher on the head and appear to point upward. McMonagle releases the tadpole back to the stream, and we march on.

Along the way, we see more tadpoles, some larger than others, and for a few exciting moments, Jennings thinks they may be yellow-legged offspring. Then he spies an adult tree frog on the side of a rock. It is only about an inch long and almost exactly the same color as the granite boulders that line the stream.

Tree frogs are fairly abundant throughout the state, especially in coastal areas. Finding them here is not a surprise. Nevertheless, Jennings takes out his camera to photograph them. He never assumes that a frog population will be there in the future. Later, after we’ve hiked as far as we can, Jennings places one of the frogs and a tadpole in a jar of formaldehyde for inclusion in the California Academy of Sciences collection. They will be evidence for herpetologists that these animals once lived here.

THE DAY AFTER THE desert hike, Jennings and I are standing on a mountain in the San Jacinto Range, contemplating which hard-to-see path might lead to the headwaters of a stream. Mike Hamilton, who has spotted mountain yellow-legged frogs on this stream, led us as far as the path’s steep beginning. That was an hour ago. Jennings is skeptical the frogs are here because he and Hayes searched the area last year and found nothing. Yesterday’s wild-goose chase in the desert below these mountains bolsters his skepticism.

It is at times like this that Jennings feels most frustrated, he says. It is late in the breeding season, which generally runs from March through June here, and it is the fourth year of a searing drought. If frogs do exist under these conditions, they are likely to be in high, isolated ponds that are difficult to get to. Once he finds them, he will have little time to observe their behavior or analyze their living conditions before he moves on to another site.

“This is the first time I’ve really been out in the field here and it’s late in the season,” he grouses. “Heck, I should have been out in the field in the springtime, but you can’t do that if you have another job. The ideal situation would be to be out there wandering constantly, almost year-round.” It would be long-term, labor-intensive observation, the kind of work that has become almost a lost art, he says.

A bed of dried leaves and needles makes the path up this mountain slippery. After an hour, and out of breath, we come to a flat spot that looks out over a range of mountains. The spot is bordered on one side by boulders as big as trucks. We wander among the boulders for a few moments, looking for the path when we finally see below us the canyon Jennings has been told that the frogs inhabit.

“I don’t hear any water,” Jennings says. He takes a few steps toward the dry stream bed. “I take that back, I take that back. I see water.” He hurries down the slope to the water hole and disappears under a canopy of trees and bushes for a few minutes before I see him scramble back up the slope to report what he’s found. “This is what I call hanging-on-by-your-toes habitat. Real marginal.”

He heads back down to the stream bed, and while I’m working my way around a boulder, he asks if I see any water from my perch. I say no. Then, as calmly as anyone can after having spent two days under a brutal sun looking for something that might not exist, he announces: “Well, there are two frogs in that hole right below you. . . . I’m sure they’re mountain yellow-leggeds. I saw them jump in.”

For the next half-hour, we move up the stream bed, looking for other frogs until Jennings hits a high spot that during the rainy season--when there is a rainy season--must be the ledge of a small waterfall but is now the site of a large puddle. Jennings climbs up and begins to describe what he sees while I poke around just below, trying to find an easier path up.

“You’ve got a pool here that’s basically four feet long, three feet wide, and a foot deep. Period,” he says. He counts 22 frogs, all lolling along the edge of the pool before they see him and dive underwater for cover. “It’s amazing they’re holding on in something like that. I mean, you think about it, their whole world is that big six months out of the year.”

At last I find a way up the ledge and get to see for the first time what it is we’ve been looking for. The mountain yellow-leggeds are small and plump. Their olive bodies are only about two inches long. Their hind legs are marked with yellow. Jennings gently lifts one out of the water and smells it to see if it has the species’ distinctive garlicky odor. It does.

This is the first recorded sighting of mountain yellow-legged frogs south of the Sierra Nevada since 1980. They were widely seen in the San Jacinto Mountains and the San Gabriels until the 1970s; then they disappeared. Nobody knows why.

Within a few minutes, the delight of finding this rare frog colony erodes as Jennings considers its chances for survival. Its tenuous hold on life is like that of the California red-leggeds he’s been counting. “You’ve got these isolated pools. I’d feel better if (they) had more water,” he says as he hovers over the frog pool. “I’m happy I found them. But this is not what I call high-class habitat.” The number in this population is so low and the living conditions so marginal that Jennings knows it would take only one small disaster--a flash flood or an impromptu convention of raccoons--to wipe out these yellow-leggeds. On the brighter side, though, this discovery so far up the stream makes Jennings wonder if there may be other undiscovered populations in isolated canyons in these mountains. Just one or two populations like this on a branch of this stream would double this frog’s chances for survival in this canyon.

Jennings contemplates hiking farther up the hill to see if there might be another pool or two. But time is working against him. He has a long drive and one more night of counting California red-leggeds ahead of him. He hesitates, then swings his day pack over his shoulders, adjusts the brim of his hat and begins the long hike down the mountain.

Early tomorrow he will return, trek back up the hill and search out this small frog family again. He’ll take more time to watch this rare group and record details about it and its surroundings. Then the notebook-toting naturalist will hike farther up the canyon to look for more mountain yellow-leggeds--just one increasingly rare and fading breed looking out for another.