Marking Penguins for Study May Do Harm

Bands used to tell birds apart affect reproduction and survival.

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By Susan Milius, Science News

A 10-year monitoring project has found that the metal identification bands that researchers attach to penguin flippers can cause long-term harm to the birds and possibly to research results too.

Scientists trying to tell one tuxedoed bird from another—no small task—in some cases wrap metal strips carrying ID numbers around the narrow part of the flipper near the bird’s shoulder. On an Antarctic island, king penguins banded this way had 39 percent fewer chicks and a 16 percent lower survival rate over a decade than did colony mates carrying just an electronic tag, an international team reports online January 12 in Nature.

And in another worrisome development, the flipper-banded penguins averaged 12.7 days away from home on foraging trips instead of 11.6. “One day or two days is a huge difference,” says ecologist and study coauthor Claire Saraux of the University of Strasbourg and France’s CNRS research network. Chicks back at the breeding site eat only when a parent swims home with food collected hundreds of kilometers, sometimes thousands of kilometers, away. And young chicks have to build up reserves to survive their first winter, when parental food delivery drops off to only a few times during the whole season.

Slower foraging fits with worries that flipper bands may be increasing drag on penguins during swimming, Saraux says. In a swimming test in a tank, an Adélie penguin wearing a band expended 24 percent more energy than an unbanded penguin.

“From an ethical point of view, I think we can’t continue to band,” Saraux says.

Flipper bands may not be good for science either, she says. Biologists are studying penguins to understand the effects of climate change on life in Antarctica, but in the new study researchers found that environmental conditions affected banded birds more severely than their unbanded counterparts. For example, during the warmer phases of the El Niño climate cycle, when the seafood that penguins eat is scarce, the banded birds showed an even greater tendency than usual to arrive late at breeding grounds.

“I don’t mean there is no effect of climate,” Saraux says. The size of impacts detected, however, may be muddied by the flipper bands.

Banding differences showed up in a study of 100 electronically monitored king penguins, 50 of which also carried flipper bands. The electronic tags are the same kind of skinny transponder that is used to identify pet cats and dogs. The tags don’t emit a signal, but reflect back a signal sent by a transmitter when a tagged animal comes near. For penguin colonies where researchers can bury transmitters along a few entry points, the tags work well, Saraux says. For colonies with wide-open borders, using the tags poses a challenge.

“All bands are not created equal,” objects P. Dee Boersma, a biologist at the University of Washington in Seattle who has studied several penguin species. Material, design and fit can alter the properties of a band just as they do rings on human fingers. “Haven't you had rings that catch on things easily and others that don’t?” she asks.

With such differences, she resists generalizing about bands: “In my view the main point of the Nature paper is that the bands they used were bad for king penguins at their location.”

Arguments over the effects of bands have been going on for years, and Rory Wilson of Swansea University in Wales raises the hope that “someone will think outside the box and produce a completely new innovation that will solve the problem.”

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