Are they really extinct? Searches for plants and animals so rare that they may not be there at all.

After 22 years, is it time to give up looking? Are searchers deluding themselves when they refuse to say that long-sought species have gone extinct? Such questions come to mind when talking to botanist Larry Morse of NatureServe, a biodiversity conservation group in Arlington, Va. Every summer since 1980, he's looked for a little tidal-flat plant called Micranthemum micranthemoides.

The plant is currently too rare to qualify for the U.S. endangered species list; Morse can't demonstrate that even a single M. micranthemoides remains on the planet. Legally, and logically, something has to exist to be endangered.

The last record of the plant dates from Sept. 13, 1941. That day, Harvard botanist Merritt Lyndon Fernald collected the plant's low-growing, round-leaved tuffs in two places along the edge of the Chickahominy River in Virginia. What happened to the species after that, nobody knows.

Morse has carefully searched the places recorded on Fernald's samples as well as all 10 sites mentioned on labels of the other known specimens. He's also visited more than a hundred additional sites with similar soil and tides throughout the species' mid-Atlantic range. In 22 years, he's turned up not a single M. micranthemoides.

So, is it time to declare an end to the quest? "Oh no," he says. "There's still plenty of habitat to look at."

Morse's search isn't rousing the public enthusiasm kicked up by the January-February 2002 efforts to find another possibly extinct species, the ivory-billed woodpecker (SN: 3/2/02, p. 141). Once the largest woodpecker in the United States and second largest in North America, the bird stretched some 20 inches from its brilliant red crest to the base of its dark tail. An international team sighted no ivory-billed woodpeckers during a month of combing woodlands in southeastern Louisiana as reporters chronicled developments for CNN, the Wall Street Journal, USA Today, and other news outlets not known for bird reports.

Most zoological and botanical search efforts don't make headlines when they come up empty-handed. Some conservation groups have guidelines for when to declare a hunt over and an organism gone. Yet when it comes to hope, searchers for species presumed extinct still make their own rules.

THE E-WORD To explain the passion behind some of these last-ditch searches, Nigel Collar turns to the cautionary tale of the Cebu flowerpecker in the Philippines. An ornithologist in Tring, England, at the Natural History Museum's bird division, Collar edited a series of books on threatened birds and knows plenty of extinction horror stories.

The little flowerpecker lived in forests on the island of Cebu, but as land clearing accelerated in the past century, biologists began to fret over the bird's fate. In 1959, a Philippine biologist reported that the island had no more forests and presumably no more flowerpeckers. The case became a textbook example of how destroying habitat can wipe out an animal. "Everybody just gave it up," says Collar.

In 1992, however, a birdwateher visiting the island spotted Cebu flowerpeckers in a leftover scrap of forest. Surveys have now turned up a few birds that have survived in improbably small woodlands, but the species' future looks far from promising.

Collar charges that the premature declaration of extinction wasted 33 years that conservationists could have dedicated to preserving the birds. Even in 1959, conditions were far more favorable to flowerpecker survival than they are today. "The patch of forest was much bigger," Collar says.

Improbable as the 1992 discovery was, now and then other seemingly extinct species return from oblivion. For example, in the mid-1980s, a western naturalist touring a bird market in Thailand saw a captive Gurney's pitta. This species, known only from Myanmar and Thailand, has black plumage marked with brilliant yellow and blue. "A pitta is a staggeringly beautiful animal," says Collar.

Ornithologists had searched lowland forests for it during the two previous decades but failed to find it. The discovery of the market bird eventually led scientists to a hilly woodland fragment with a few dozen of the birds. Their future looks precarious, but today the species certainly isn't extinct.

Estimating the chances of such rediscoveries is tricky, according to Craig Hilton-Taylor, who compiles the Red List of imperiled species for the IUCN-World Conservation Union based in Gland, Switzerland. The 2000 edition of the list ranked 766 plants and animal species as having gone completely extinct during the past 500 years and 50 having become extinct just in the wild. Since that publication, Hilton-Taylor says, rediscoveries have justified reclassifying two of the extinct species: a plant that's a close relative of the national flower of Mauritius and the Bavarian pine vole.

The vole was unusual even for a rediscovery, says Hilton-Taylor. So many people, including biologists, crowd into Europe that its flora and fauna hold fewer surprises than do those of wilder regions of the world. Biologists had found the vole only at one site and had given up hope for the species after a hospital complex obliterated that German habitat. Yet, last year, a Bavarian pine vole turned up in a trap in Austria.

In the United States, NatureServe--and before it, the Nature Conservancy--has reclassified one or two species a year from lost to living, says Morse.

Are species being written off too soon? According to IUCN policy, a species is declared extinct "when there is no reasonable doubt that the last individual has died." IUCN directs Red List assessors to consider the quirks of the organism. Have surveys covered the appropriate times of day or year? Have they lasted long enough, considering the individuals' life spans? The list's commentary cautions that accumulating evidence of extinction "could take a very long time" in some cases. The IUCN gives as an example an orchid that blooms, briefly, only after wildfires that strike about every 25 years.

BACK FROM OBLIVION Finding those last few survivors often takes a new point of view and old-fashioned luck. Pamela Rasmussen of Michigan State University in East Lansing discovered a missing owl in India after realizing that earlier searchers had combed the wrong habitat. Analysis from the FBI helped, too.

When Rasmussen began writing a field guide to birds of the Indian subcontinent, she noticed that several species had not been reported in decades. One such bird, called the forest owlet, purportedly occupied a broad swath of populated, accessible central India. "It's not where you expect a mystery bird to be," she says.

Descriptions of the bird came only from the seven existing stuffed specimens, the most recent of which had been supposedly collected by Col. Richard Meinertzhagen in 1914. At the Natural History Museum's bird division in Tring, England, Rasmussen was plowing through the registry of specimens from another collector, James Davidson, when she noticed a listing for a forest owlet that hadn't been among the set of specimens she'd studied. She knew that a modern ornithologist had reported that Meinertzhagen had pilfered other collectors' specimens. Could he have stolen the owlet and presented it as his own--with an altered location description?

The British museum permitted an expert preparator at the Smithsonian Institution in Washington, D.C., to examine the so-called Meinertzhagen owlet specimen. A good look at the bird's wing revealed bits of old, stained cotton stuffing. The only collector of that period who tucked cotton into bird wings was Davidson. An FBI fiber expert confirmed that the remnants match cotton in Davidson's known birds.

Using the location for the last sighting of the bird according to Davidson's records instead of Meinertzhagen's, Rasmussen narrowed the bird's confirmed range to two areas. She also developed a new list of ways to identify the bird in the field.

A Smithsonian colleague gave Rasmussen odds of one in a thousand for finding the species during a short trip to India. In 1997, though, she and two other birders gave it a try. At the second site they checked--at 8:30 a.m. on their first day there--one of Rasmussen's fellow searchers spied a forest owlet sitting on a branch near a dirt road. The team videotaped the accommodating bird through a bird-watching scope.

LOCATION, LOCATION, LOCATION Habitat analysis like Rasmussen's underlies many of the rediscovery successes. However, herpetologist Gordon Rodda wasn't analyzing habitats when he first met Guam's slender-toed geckos.

The name comes from the gecko's unique toes, which have no pads. Other Guam geckos have pads that help them race up slippery wet leaves, but the slender-toed ones stick to rocks and other rough, easy-to-grip surfaces. These animals have no males, and the females lay eggs that develop without fertilization.

Slender-toed geckos remain on a few Pacific islands, but the population on Guam had gone missing after World War II. Or so Rodda thought. In 1996, he was trapping species in an undersurveyed area--near a former storage area for nuclear weapons--and caught a slender-toed gecko. Another showed up under an old mattress that had been tossed into the shrubbery on a different part of the island, and Rodda eventually found enough animals to piece together their distribution. They had survived mostly on parts of the island that had been by an alien invader, the brown tree snake.

Rodda, now at the U.S. Geological Survey in Fort Collins, Colo., offers an explanation for this peculiar pattern. He suggests that the snake, generally a regrettable addition to Guam's wildlife, helps the geckos by keeping in check another invader, a big musk shrew that eats ground-dwelling creatures. The other islands that still have slender-toed geckos have escaped this shrew's invasion, so far.

Rethinking a habitat also led to the rediscovery of the Yadkin River goldenrod in North Carolina. The plant takes its common name from the only river, in central North Carolina, where botanists have found it. Scientifically described in 1896, the goldenrod "fell out of people's consciousness," says botanist Alan Weakley, now of North Carolina's NatureServe office in Durham. The few people, including Weakley, who did think about the goldenrod assumed that two dams built on the river had covered the plant's habitat with deep water.

Weakley was tramping around the region surveying plants along the Yadkin in the fall of 1994, when he noticed a peculiarity on the aerial photos he carried. They showed what looked like a quarter-mile stretch of original riverbank still intact between the two dams. Weakley drove over to see if some goldenrods had indeed escaped flooding. "I thought there was a pretty good chance, but then I thought it couldn't be this easy," he says.

It was. A road took him to within 100 yards of the riverbank, and he climbed down to find hundreds of the bright yellow flowers leaning over the water. Weakley ended up sharing the honors of rediscovery with local plant sleuth Steve Leonard, who independently visited the same spot 3 days later.

Wildlife Conservation Society biologist Peter Zahler of Pelham, Mass., didn't have such an easy trip to potential habitat for woolly flying squirrels. In the early 1990s, Zahler studied records of the animal in Pakistan. With a 2-foot-long body and a tail the same length, the heavily furred squirrel had been ranked as the world's longest. Yet the last record of the squirrel came from 1924, when a British colonel photographed one being led around on a rope.

Few western biologists had recently visited the highly books warn of murderous local feuds in the isolated valleys. Nonetheless, Zahler began working his way through the valleys--at his own expense--in 1992. He set live-capture traps and, through his interpreter, politely quizzed locals about the squirrel. They told him plenty of legends but assured him the animal was extinct.

Yet the area's abundance of caves and other potential hiding places for large squirrels impressed Zahler. "There could be a squirrel party on a ledge 20 feet above my head, and I'd never know," he says. He convinced the World Wildlife Fund of Pakistan to contribute funds for a second trip 2 years later.

Again, he traveled in the valleys, set traps, and talked to about the squirrel. He continued to hear tall tales, such as of squirrels that used to milk cows at night. One guffawing policemen made Zahler's girlfriend leave the room and then confided that aged, rocklike squirrel droppings have aphrodisiac powers.

Two men who later dropped by Zahler's camp asked if he'd pay for a living squirrel. He said, "Sure," but didn't expect any deal. They surprised him by returning in a couple of hours with a live woolly flying squirrel in a bag. He learned that they were aphrodisiac dealers who collected the droppings from caves. By finding more of these entrepreneurs, he's now located evidence of the squirrels throughout the Diamer region. Even with the best habitat analysis in the world, an extinct-species rediscoverer still needs luck. Larry Morse hasn't had much in the Micranthemum department, but he has had other bright moments. One of his searches revealed a low-growing, mat-forming plant on the Chickahominy River's tidal flats. It wasn't Micranthemum, but it was another lost species, a small mudflat creeper called Bacopa stragula.

No one had reported seeing it for years, but it wasn't truly extinct, Morse found. Someone just needed to look in the right place.