Tom Anton is into herps. Always has been, at least from age six or seven, when he came home with a garter snake and asked if he could keep it. He could, and did. Next came a turtle, then frogs, toads, salamanders, fish. By the time he was in high school his mother refused to enter his room because of all the snakes.

Recently, on a steamy late August morning, Anton was exercising his herpetological obsession at Big Bend Lake in Des Plaines. Anton, who is now a wildlife biologist working for the Forest Preserve District of Cook County, was looking for frogs. Green frogs, in particular.

Big Bend Lake is popular for fishing, as evidenced by the detritus along the shore: beer cans, empty bait containers, discarded fishing line. The grass surrounding it was mowed to within a foot or two of the water. Anton was not optimistic about the prospects. “My concern is that they’re wiping out green frogs in a place like this,” he said. “Where you have a lot of cattails and aquatic vegetation green frogs and bullfrogs can coexist. But when the grass is mowed almost to the edge the bullfrogs eat the green frogs.”

Bullfrogs–which are large, aggressive, and highly adaptable–can live almost anywhere. Green frogs cannot. They are only one of a number of threatened herps–reptiles and amphibians–in Cook County forest preserves. Anton’s job is finding them and trying to figure out how to make sure they stick around for a while. To that end he is working on the first detailed herp census to be conducted in the area since the 1940s. The result is that Anton gets to spend some of his days doing just what he liked to do as a kid–poking around woods and marshes, getting wet and muddy, and looking for creepy-crawly critters that most people shudder at.

Cook County, with its abundant wetlands and patchworks of forest and prairie, has always supported a rich variety of reptiles and amphibians. But the average visitor to a forest preserve wouldn’t know it. Bullfrogs and green frogs, which may jump abruptly into a lake when startled, are at the obvious end of the scale. Other species can exist for years or decades in a preserve without anyone knowing they’re there.

Anton’s destination on this day was a sedge meadow on the other side of Golf Road from Big Bend Lake. He hoped to find a Kirtland’s snake, a secretive species that has not been seen in the area for ten years. That doesn’t mean it’s not there anymore. Kirtland’s snakes are rarely seen. They tend to hide underground, hunting in burrows that crayfish excavate in wet meadows. Only in April and May, when males and females seek one another, do they commonly travel far from home.

After a half hour of scanning the lakeshore, fruitlessly, we headed over to the sedge meadow. It’s a weedy, unkempt place that runs from forested land down to the Des Plaines River. Here and there it sprouts into thickets of buckthorn, but for the most part it is wide-open. Crews trim the brush every year or two because there’s a high-tension power line overhead. The openness and the wetness are ideal for crayfish, and for the snakes that eat them.

Scattered through the meadow are decaying portions of railroad ties, other boards and logs, and a few rusting pieces of corrugated metal. They too make this good snake habitat. “Basically what I do to look for snakes is look for cover objects, like this board, then turn them over and see if anyone’s home,” Anton said.

He flipped a weathered board. A golf-ball-sized hole led into the firm mud under it–a crayfish burrow. But no one was home. Anton laid the board back. Maybe next year. “My favorite places are places like this, anyplace you find old boards, chunks of tin, collapsed farm buildings,” Anton said. “I could spend hours turning over boards. A lot of times biologists are never as happy as when they find a pile of junk. It’s amazing how unsightly garbage can become home to snakes and other herps.”

And that was how we spent the next half hour, flipping over boards and logs, stumbling over clumps of goldenrod. We found nothing except spiders, crickets, seething masses of ants, and lots of crayfish burrows–until Anton spotted a pile of old, broken plaster-and-chicken-wire sheets. He said he had a good feeling about it, then cautioned, “Sometimes paper wasps build their nests in places like this. That’s unpleasant.”

Anton lifted one end of a large sheet, then darted his free hand underneath. “A plains garter snake!” he yelled and lifted a squirming snake up. It was beautiful–black and yellow, with a setting-sun-orange stripe down its back. It writhed in his hands and squirted a musky, acrid-smelling substance intended to ward off predators.

Anton was unfazed. “These are probably the most common snakes in Cook County–very successful animals,” he said. “Wherever you find them they’re probably in very large numbers.”

Sure enough, he soon found another one in the plaster pile, then an eastern garter snake and a northern leopard frog–also both common species. But we’d reached the end of the meadow, and there was no sign of the Kirtland’s snake.

Not finding it didn’t mean much. “This area hasn’t changed much since the Kirtland’s snake was found here ten years ago,” Anton said. “It’s still a power-line corridor. The crayfish are obviously still here. The sedges are still here. But you never know what sorts of changes might make an area unsuitable. There may have been changes in the groundwater that the crayfish could adjust to but not the snake.”

Or maybe not. It’s very difficult to prove the fact of absence. Only repeated surveys over years can prove whether a secretive species has vanished from a particular preserve. Even then there are always surprises. Five years ago Anton achieved a modest measure of local herpetological fame when he found a closely related species, a Graham’s crayfish snake, in Cook County, where no one had seen one since the 1940s.

The Cook County herp census–which is funded by the U.S. Forest Service–is an element of a nationwide network of biologists who are conducting amphibian inventories around the country. Biologists have noted global declines in populations of many species, especially frogs. Because they live both on land and in water, and because their thin, permeable skins allow pollutants to enter easily, frogs are particularly sensitive to environmental changes.

Most worrisome are declines in species whose habitats are protected. Some biologists have speculated that acid rain and increased ultraviolet radiation–caused by thinning of the atmospheric ozone layer–are to blame. But considerably more research is needed before that can be proved. The baseline data that Anton’s team is compiling will be a very small part of that big picture.

Most of Cook County’s preserves are protected from development, but Anton points to a number of local factors that may contribute to the rarity of some herp species. Collectors illegally swipe some specimens. “On the weekend before a reptile and amphibian swap meet,” Anton said, “you’ll notice an increase in activity in forest preserves–people running around with buckets and bags.”

Bullfrogs–whose naturally occurring numbers are augmented with released pets and with tadpoles used as fishing bait–can decimate populations of smaller frogs. Even weather patterns can make a difference–this cool, wet spring and summer seems to have benefited most amphibians.

But the largest threats to species survival are changes in habitat. Anton has seen a number of favorite herping locales turned into malls and subdivisions. “As private lands get developed, the only places these animals have to rely on are the narrow forest preserve corridors,” he said. “Species like large snakes need a lot of room and can easily be harmed by habitat isolation. We’re seeing populations get compressed to the point where they may be getting inbred. Inbreeding causes the genetic variability to decrease, and you get the possibility of birth defects, or normal-looking animals with abnormalities in behavior.”

Even protected lands can change and become inhospitable to some species. One of the animals Anton is most interested in finding is the wood frog, a highly secretive species that relies on wet woodlands. It needs meltwater pools for breeding and plenty of moist leaf litter for hiding. Wood frogs are known to live in only a few places in the county.

Anton worries that the current enthusiasm for restoring closed woodlands as open, drier savannas may threaten the frog, along with several salamander species that also like it wet. “The wood frog is probably the species most threatened by excessive savannaization,” he said. “But there’s got to be a balance somewhere where we’ll have both savannas and moist woodlands.”

After searching for snakes in the sedge meadow we ran across Golf Road to the bank of one of the Des Plaines River’s lazy backwater sloughs. A fallen dead tree, long since stripped of its bark, lay in the muddy water. Anton spied two turtles basking on it. They were flat, brown, the size of dinner plates–female softshell turtles, he said, big ones. We crouched on the wooded bank to watch them–Anton said softshells are curious but wary, sensitive to disturbance. We watched as each one slowly slid into the water to cool off or hunt for minnows, then crawled back out again a few minutes later. They looked antediluvian, prehistoric. And only 20 yards away four lanes of traffic roared by.

“Two big turtles like that, that’s a good sign,” Anton said. “That’s what I like to see.”