Even the most discerning human has trouble telling one penguin from the next. So researchers often place a small metal band inscribed with an identifying number around each bird's flipper. But what's good for scientists may be bad for penguins. Researchers have found that penguins wearing flipper bands produced fewer chicks and were more likely to die than were penguins with no bands.
The first evidence that flipper bands might cause harm came in the 1970s, when zoos reported that the bands could wound penguins' flippers, especially during the annual molt, when flippers swell. Since then, several groups have tried to determine whether the bands have an impact. The results have been mixed, with some studies finding an effect and others reporting no difference.
Still, some researchers stopped using the bands. For example, Yvon Le Maho, a physiologist at the French National Center for Scientific Research's Centre d'Ecologie et Physiologie Energétiques in Strasbourg, France, began using RFID tags, electronic chips that are injected under the penguin's skin instead of bands. These chips emit radio waves that the researchers can use to track the penguins' movements. Bands have one major advantage over electronic tags, however. They are visible. The only way to track penguins using RFID tags is to place antennas anywhere the animals might move.
In the late 1990s, Le Maho decided to try to settle the debate over banding. He and his colleagues chose a colony of king penguins on Possession Island, a 150-square-kilometer patch of land roughly 1000 kilometers from Antarctica. More than 400 of these birds had already been tagged with RFID chips. The researchers randomly selected 100 of these birds and placed flipper bands on half. Using antennas buried underground, they tracked the birds' movements from 1998 until 2008, making this study the longest to compare banded and unbanded birds.
Overall, the team found, bands were bad for penguins. Banded penguins had a 16% lower survival rate than unbanded birds over the 10 years, the researchers report online today in Nature. Banded birds also arrived later at the breeding grounds and took longer trips to forage for food. As a result, they produced 39% fewer chicks.
Le Maho and his colleagues believe that these ill effects are the result of the bands causing drag when the penguins swim. So banded birds must work harder to travel the same distance. Some researchers have suggested that penguins adjust to the bands over time. But Le Maho observed that although most of the mortality among banded birds occurred in the first 5 years of the study, the effects on foraging lasted for a full decade.
Whether the bands had an effect depended in part on the availability of food in a given year. For example, when resources were plentiful, the researchers did not observe much of a difference between unbanded and banded penguins. So studies that only last a year, Le Maho says, may not find that banding has any effect.
Le Maho points out that his team's results suggest that research using banded penguins may be biased. For example, he says, several high-profile studies have used banded penguins to investigate the impact of climate change on the birds. The findings of those studies aren't necessarily wrong, but the numbers need to be reconsidered, he says.
David Ainley, a marine ecologist with H.T. Harvey & Associates, an ecological consulting firm in Los Gatos, California, says the group's findings are important. He points out, however, that "most data on the effects of climate change on penguins are not derived from banded studies." Instead, researchers rely on annual censuses conducted using everything from satellites to aerial photographs to ground counts.
Dee Boersma, a conservation biologist at the University of Washington, Seattle, says flipper bands likely do have some harmful effect, but the severity of the effect depends on the species of penguin being studied and the type of band used. "What they show is that their bands harm king penguins," she says. Boersma says that she and her colleagues have not observed the same detrimental effects of banding in the Magellanic penguins that they study in Argentina.
Le Maho would like to see an end to flipper banding, but Ainley says that's unlikely to happen in the near future. Studies that track penguin dispersal would be nearly impossible without the use of flipper bands, says Ainley. "There are questions that need to be asked and answered that RFID can't do and that banding can."