How reliable are the traditional method of counting wildlife animals to know their numbers for purposes of conservation?

Scientists have shown that they are quite unreliable, and can lead to significantly incorrect totals that they believe could adversely affect conservation efforts. They found genetic methods to be far superior.

Andrew DeWoody, a professor of genetics at Purdue University; Jamie Ivy, population manager at the San Diego Zoo; and Todd Katzner, a research assistant professor at the University of West Virginia, found that visual counts of imperial and white-tailed sea eagles in the Narzum National Nature Reserve of Kazakhstan significantly underestimated the imperial eagle population there. Using DNA from eagle feathers gathered in the area, the researchers were able to identify individual DNA fingerprints for each bird.

The proof

The technique showed that there were 414 eagles, more than three times as many as had been visually observed, and more than two and a half times more than modelling suggested would be there.

“A biologist doesn't always see them coming and going,” said DeWoody, whose findings were published in the early online version of the journal Animal Conservation.

“Eagles are difficult to capture, mark and resight. Biologists in the field can't differentiate individuals, whereas by a genetic fingerprint geneticists can differentiate among individuals that have visited a site.”

They collected thousands of eagle feathers around roosts and nesting sites. They extracted DNA from those feathers and determined that there were hundreds of eagles that had recently visited the site.