A well-designed scientific experiment shouldn’t affect the behavior of its subjects or cause them harm. Yet that’s exactly the result of using flipper bands to identify individual penguins during field studies, one team of researchers now contends.
In recent years, scientists have increasingly looked to penguins as a source of data about climate change. The new evidence comes from a long-term field experiment conducted on a remote island in the southern Indian Ocean that was designed to do just that. From 1998 through 2008, a team led by Yvon Le Maho, an ecophysiologist at the University of Strasbourg in France, monitored 100 king penguins on Possession Island, a 150-square-kilometer landmass in the windswept Crozet archipelago. Le Maho and his colleagues implanted the penguins with transponder tags — similar to those implanted in pet dogs and cats — that allowed researchers to track the comings and goings of the majestic birds in the breeding colony there. But 50 of the birds in this experiment were also tagged with a metallic band around one flipper, the standard technique scientists have used to monitor penguins for decades.
Over the course of the team’s 10-year study, unbanded penguins fared much better than their banded brethren. Birds tagged with flipper bands had a lower long-term survival rate — dropping by 16 percentage points, or about 44 percent overall (note this was incorrectly reported in the original paper, a point picked up by AP journalist Seth Borenstein). Banded birds also had about 40 percent fewer chicks than unbanded birds did, the researchers report in the January 13 issue of Nature.
There could be any number of reasons for the dramatic disparity, says Rory Wilson, an aquatic biologist at Swansea University in England who was not involved in the research. For one thing, the glint from a metallic flipper band may actually attract the attention of predators. Prior research shows that penguins tagged with a flipper band use 24 percent more power when swimming than unbanded birds do, a measure of the drag caused in part by turbulence in water flow over the penguins’ flippers. Because of the increased drag, the birds deplete their oxygen supply more quickly when diving, chasing prey or eluding predators.
Some previous field studies have found no detrimental effects of flipper bands on penguins, but data gathered by Le Maho and his team help explain why. In years when food is overly plentiful, all birds can get by, and in lean years all birds suffer. Only in normal years do the injurious effects of the flipper bands become statistically apparent, the team found.
Results of the new study call into question the use of flipper bands in penguin studies and cast doubt on many data gathered during such field experiments, says Le Maho.
Check out Nature’s video of the penguins that took part in the study here.