Reappearing act

The conservation world shuddered when scientists declared Miss Waldron's red colobus monkey extinct in 2000. Believed to be the first close relative of humans to disappear in more than two centuries, the little monkey's loss dramatized the need to save West Africa's remote forests and stoked fears of an extinction wave across the continent.

Now, just like the ivory-billed woodpecker that made a Lazarus-like appearance in Arkansas two weeks ago, Miss Waldron's monkey may be alive after all. An article in the June International Journal of Primatology will document tantalizing evidence of the animal's existence in the remote reaches of southeastern Ivory Coast.

Extinction, it turns out, may not always mean forever. As researchers rush to document the world's fast disappearing species, the ''gone-for-good" label has become peppered with reversals, ambiguity, controversy and intense public interest. Proving the absence of a species is exceedingly difficult. Scientists argue over how long a final search for a species should last. Others disagree over which groups of organisms can even be declared extinct. The answers are important, researchers say, because conservation efforts are often molded around species at risk for extinction -- particularly charismatic ones.

''Species close to extinction are generally recognized as priorities for conservation. . . . You want to get it right," said Weston-based Larry Master, chief zoologist for NatureServe, a nonprofit group that assesses the status of species and ecosystems. The group says that every year a few US species of plants, animals and insects are rediscovered.

''It's not good for scientific credibility to have these [species] coming on and off the lists all the time," Master said.

Recovery attempts are abandoned if species are unquestionably gone for good, such as the heath hen that was last seen on Martha's Vineyard in 1932. But many species declared extinct these days are really only presumed extinct -- so interest remains high to preserve their habitat and to search for stragglers that may determine the species' survival.

The reported deaths of dozens of species have been, in Mark Twain's words, ''exaggerated." The Bavarian pine vole, a tiny mousy creature, was thought to have gone extinct in Germany decades ago after a hospital's construction destroyed its only habitat, according to news reports. Then, in 2000 the vole was discovered in Austria.

A year later, the Lord Howe Island stick insect -- as long as a hand and often called a walking sausage -- was found on a hard-to-reach rocky outcrop off Australia 80 years after it was presumed extinct.

Last week, three species of snails previously thought extinct were discovered in Alabama.

While scientists can look for decades or even generations for individuals of a species, the possibility always exists that they missed one. Indeed, scientists often remind themselves that they thought the prehistoric coelacanth fish was extinct for 65 million years -- that is, until one was caught in 1938.

''Many creatures are small or inconspicuous and it's really hard to tell even when they are around," said James Hanken, director of Harvard University's Museum of Comparative Zoology. ''When they are gone, it's even harder to know."

Scientists differ over how long a species should be searched for -- or just not seen -- before it is declared extinct. The IUCN-World Conservation Union compiles a well-known ''Red List" of threatened species that defines their extinction when ''there is no reasonable doubt that the last individual has died."

''It's a slow accumulation of negative evidence . . . there is a lot of debate," said Craig Hilton-Taylor, Red List program officer. According to his group, at least 15 species have gone extinct in the last 20 years and another 15,589 are at risk of extinction.

The Red List, which is known for being conservative, did not include the ivory-billed woodpecker, nor Miss Waldron's monkey, as extinct. Rather, they were presumed extinct by researchers and repeated media accounts.

Others, such as Ross MacPhee, co-founder of the Committee on Recently Extinct Organisms based at the American Museum of Natural History in New York, said scientists should wait at least 50 years since the last sighting to be sure a species is really gone.

Sparking even more debate is which groups of organisms should be listed. The conservation union tries to only list true species, but has been known to list isolated populations or even subspecies to preserve genetic diversity, or because the organism is associated with a specific geographical area. But the Committee on Recently Extinct Organisms says only true species should be listed.

''There is a continual bell-ringing for the extinction crisis," said MacPhee, curator of vertebrate zoology at the American Museum of Natural History in New York. ''All these definitions are stretched to the utmost to say this species is about to go [away]."

MacPhee worries that environmental groups are capitalizing on the extinction crisis to raise money or to focus conservation efforts on organisms, ecologically speaking, that may not be the most critical to save given a limited amount of funding. He and other scientists say public attention is much better focused on keeping ecosystems intact than on saving single, imperiled species.

Miss Waldron's monkey illustrates the extinction definition problems. The monkey, named for the traveling companion of the man who discovered it in 1933 in what is now Ghana, may not be a species but rather a subspecies of other red colobus monkeys found in the area.

And, while it may now be alive, many scientists really thought it was gone: The last confirmed sighting was in 1978 and researchers spent six years combing the high-canopy forests in Ghana and the Ivory Coast for it with no luck. The creatures' numbers have been sliced because of habitat destruction and hunting, researchers say.

Scott McGraw, an associate professor of anthropology at Ohio State University, cowrote the 2000 research article that concluded the monkey was probably gone for good. Shortly afterward, he went back to the Ivory Coast only to be handed a tail of a Miss Waldron's. The year after that, a hunter he knew gave him a skin with freshly dried blood, a sign that at least one existed in recent times. McGraw also received a picture of a carcass of another Miss Waldron's.

He is itching to get back to the area to look for himself, but war has prevented him from traveling there.

"The main message is this area of Africa hasn't gotten the conservation attention other places have," McGraw said. ''It's a paradox because the first evidence it's alive is dead evidence.

''I hope I was wrong."

Beth Daley can be reached at bdaley@globe.com