Fingerprints left behind at special tracking-boxes allow field biologists to identify which individual fisher had come in for the bait and, therefore, count the exact number of animals using an area. Scientists teamed with fingerprint experts at the New York State Department of Criminal Justice (DCJS) to develop this method, which is far simpler and less expensive compared to alternatives such as DNA fingerprinting.

Fisher prints differ from human fingerprints because they are made up of patterns of dots rather than ridges, so standard criminology software did not work. "We tried submitting fisher prints to the state's fingerprint database but it didn't pair up the prints well," says Richard Higgins, retired chief of the DCJS Bureau of Criminal Identification. "But looking at them side-by-side it was obvious when you had a match."

The fisher, an eight-pound member of the weasel family, is the only carnivore known to have fingerprints, which are also known from primates and koalas. Other species may also have unique patterns in their tracks that would help in counting their numbers in the wild.

"The few porcupine and opossum tracks we got had incredible patterns and will probably turn out to be unique with more study." says Dr. Roland Kays, curator of mammals at the State Museum, who co-authored the Journal article, along with Higgins and others.

"Identifying individuals allows us to actually count how many animals are in different areas, which is essential information for monitoring their conservation status," says Justina Ray, director of Wildlife Conservation Society Canada. "My hope is that we can apply this kind of inexpensive, sure-fire technology to help conserve a wide range of species, especially those that are threatened with extinction."

Scientists surveyed fishers from 2000-2002 as part of a carnivore survey across 54 sites in the Adirondack region of Northern New York. Fishers were the second most commonly detected carnivore species, behind coyotes.

"Our study suggests fisher populations are healthy throughout most of Northern New York," said Ray. "Fisher populations are rising in most of the Northeastern United States, showing that wildlife can reclaim their turf if forests are allowed to recover."

Fishers were nearly driven to extinction in the state by deforestation and over-trapping before receiving protection in the 1930s. This led to a slow recovery, and limited trapping was permitted again in the 1970s. Their recent population boom appears to have begun in the 1990s.

Fishers spread south out of the Adirondacks and Vermont and into the Hudson Valley. They are also spreading westward, with today's leading edge around Syracuse. Fishers were first recorded in the suburbs of Albany and Boston in the last six years.

The other co-authors of the Journal study are Mike Tymeson and Richard Higgins, DCJS; Carl J. Herzog, state Department of Environmental Conservation in Albany; Dr. Matthew E. Gompper, Department of Fisheries and Wildlife Sciences at the University of Missouri in Columbia, MO and Dr. William J. Zielinski United States Department of Agriculture Forest Service, Pacific Southwest Research Station, Redwood Sciences Laboratory in Arcata, CA.

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Materials provided by Wildlife Conservation Society. Note: Content may be edited for style and length.