CARDIFF -- Mosquitoes whine past Scott Smith's ears, and the noontime sun tickles sweat from his brow. Mud slurps at his rubber waders as he plugs along, ankle-deep, between the tussock sedge, skunk cabbage and jewelweeds. He freezes in this hidden bog, ringed by oak and black cherry trees, in a glade between grain fields in northern Harford County.
He squints. He grabs.
"I've got one!" he calls out, brandishing a wiggling creature a little bigger and bulkier than a cassette tape. It hisses faintly in protest and frustration, sounding like a leak in a bicycle tire.
Score one for Mr. Smith, a 32-year-old wildlife biologist with the Maryland Department of Natural Resources. It took him and three companions only about an hour of sloshing around to track down one of the state's shyest, most elusive creatures -- the North American bog turtle, or Clemmys muhlenbergii.
The palm-sized reptile, long considered one of the rarest turtles on the North American continent, is being stalked in scattered spots across the state this spring as part of a Department of Natural Resources survey to help decide if its isolated colonies are hanging on or flirting with oblivion.
Fourteen years ago, the state found bog turtle colonies in about 170 soggy meadows, swamps and other wetlands in northern Carroll, Baltimore and Harford counties.
Now, Mr. Smith and about 20 volunteers are trying to see how many sites still have turtles. They are also checking how many of its swampy habitats are still wetlands and how many have been drained, plowed, paved or turned into duck ponds.
Property owners, meanwhile, are being asked to help protect the fragile wetlands and report turtle poachers. (There is an active trade in bog turtles in Europe and Japan, herpetologists say, and a mating pair might bring $750 on the black market.)
With Jack Cover, curator of the rain forest exhibit at the National Aquarium, and Robin Saunders, an aquarium herpetologist, Mr. Smith weighs the small male he just captured.
He measures it and notches its shell so its movements can be tracked if it is recaptured later. Then he names it Horatio and lets it slip back into the mire.
Many farmers who have seen their share of stinkpots, snappers, red bellies and maps would not recognize the anti-social muhlenbergii if it walked up and bit them. (That is something the harmless creature would never dream of doing.)
"It's so secretive, most people have never seen one," said Mr. Cover.
Scientists think the creature, which appeared before the dinosaurs, thrived after the end of the last glacial period when extensive marshlands spread across what is now the northeastern United States. But these swamps began drying out after the Pleistocene Epoch, perhaps isolating the widely scattered turtle colonies.
Now they face a new problem: humans, and their penchant for draining swamps.
The number of bog turtles has probably fallen in recent decades, scientists think. But they are not sure whether the shelled reptiles are close to extinction or just exceedingly shy.
The first Clemmys muhlenbergii was found near Lancaster, Pa., in 1792. But the turtle was not found in Maryland until 1943, 151 years later, when an elderly male was spotted cowering under a board in a shallow stream. After feigning death for several hours, its discoverers reported, it poked its head out of its shell and urinated.
Muhlenbergii, one of 14 turtle species found in Maryland, was on the state's endangered list from 1976 to 1978, when the earlier survey found a lot more bog turtles than expected.
So it was moved to the state's "watch list," meaning it bears watching because of its limited distribution, declining numbers or special vulnerability.
Elsewhere, wildlife experts think the reptile is in trouble. Six states north of Maryland list the turtle as endangered, and Connecticut is expected to do so soon. Federal wildlife officials have made the creature a candidate for the national endangered species list.
Mr. Smith fears the population may be shrinking. A review of aerial photos, he said, suggests that perhaps a quarter of the 1978 bog turtle sites have been damaged or lost over the past 14 years.
Recent federal and state laws have halted, or at least slowed, the destruction of wetlands. The bog turtle itself is protected by another state law that prohibits the capture and collection of any non-game wildlife without a permit.
But if the turtle is found to be endangered, the state will have to come up with a special plan for protecting it.
Meanwhile, Mr. Smith's team has had a busy day.
They started at another farm where they captured a large female in an old drainage ditch. Marvin, a 72-year-old farmer who grew up in a farmhouse a few hundred yards from the ditch, and his wife, Grace, stood watching. (Biologists asked that the exact location of the turtle sites be kept secret to discourage collecting. Marvin and Grace's last name might help identify their property.)
Grace surveyed the surveyors.
"Most of the time we live back here in oblivion without the rest of the world knowing we're here," she said. "So I'm not sure I know what to think about all this."