Penguingate

Tagged penguins could skew climate studies

Tagging penguins with flipper bands harms their chances of survival and breeding, a finding which raises doubts over studies that use these birds as telltales for climate change, biologists said on Wednesday.

The metal bands, looped tightly around the top of the flipper where it meets the body, have long been used as a low-cost visual aid by researchers to identify individual penguins when they waddle ashore.

 So far, so good.  Tagging studies have been used to get data on countless species in the wild.

But, says the new study, the seemingly harmless bands affect the penguin's swimming performance, causing it to waste more energy in foraging for food, sometimes with life-threatening consequences.

Publishing in the journal Nature, French and Norwegian scientists reported that they took 100 king penguins (Aptenodytes patagonicus), selected at random on Possession Island on the Crozet archipelago, a sub-Antarctic group in the southern Indian ocean. All were tagged with a minute, electronic transponder that was implanted under the skin, which can only be read by using specialist equipment placed close to the bird. Fifty of the 100 birds were additionally given a flipper band.

The team then recorded sightings of the group over the next 10 years. Banded birds were 16 percent likelier to die than non-banded counterparts, and had 39 percent fewer chicks, they report.

King Penguin with flipper tag; the walking wounded

Not so good.  Hardly anybody would get upset if a study of house sparrows caused a little extra mortality, but penguins are a little rarer, and more charismatic.  Ooops, it's bad when your scientific study is inadvertently causing extra mortality of an animal they make animated movies about.

It seems that the Antarctic is a truly tough environment (what a shock) and that anything even marginally reduces the ability of the penguin to swim, or catch food etc, significantly reduces it's survival rate.

But how does this play into global warming studies, you might ask?  

Penguins sometimes feature in climate research as tool for measuring the impact of global warming on cold-water wildlife.

But such studies may now have to be reviewed, for penguin population data could be skewed by flipper banding, says the paper.

"During the course of our study, when the sea temperature was low and food resources were abundant, there was virtually no difference between banded and non-banded birds," explained Claire Saraux, like Le Maho a member of France's National Centre for Scientific Research (CNRS).

"However, when there was a rise in sea temperature and food was less abundant, the penguins had to swim farther, and banded penguins stayed longer at sea to forage compared with non-banded birds."

So flipper banding studies have exaggerated the effects of warm water on penguin survival, calling past results into question.