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Saturday, January 29, 2011

Penguin tagging not so innocuous

Tagging animals in order to study them is a common practice. Much information has been gained about behavior and migration patterns thanks to various labeling techniques. But do the tags have any negative effects? If you’re using flipper bands on king penguins, the answer is ‘yes’.

Claire Saraux led a team from the Université de Strasbourg and the University of Oslo in investigating the long term effects of banding on a colony of king penguins. 100 birds were implanted with electronic tags, and half of these were also fitted with flipper bands. The birds were observed over the next ten years. Compared to the birds with only electronic tags, the banded birds reared 39% fewer chicks and had a 16% lower survival rate. The increased mortality and decreased reproductivity continued throughout the entire ten-year period, indicating that the birds were not acclimating to their banded flippers as researchers had thought they would.

King Penguins (Aptenodytes patagonicus) at Edinburgh Zoo.

Photo by SeanMack, 2006.

The banded birds as a group tended to show up late to their breeding grounds, possibly because they were taking longer to forage for food. This hypothesis is born out by observations that the differences between banded and non-banded birds was minimized in years with more favorable environmental conditions.

Personally, I’ve always wondered how tagging affects an animal’s long term survival. If nothing else, it seems like the odd smell, appearance and/or texture would have to impact mating success. Prior to this study, I’d never seen any mention of this issue. Biologists always seemed to assume that their tags have a null affect on their study subjects. I should point out that one of the reasons for using wing bands rather than electronic tags is that the bands can be seen from a greater distance, presumably decreasing the stress of close human contact. This study shows that, at least for king penguins, electronic tags are preferable.

Hat tip and more details: Not Exactly Rocket Science.