22 January 2011

Is band practice bad practice?

King penguins on Possession Island.
Photo by ¡WOUW!. Some rights reserved.


A study published in the 13 January issue of Nature that shows flipper banding has a significant impact on the breeding success and survival rate of king penguins has reignited a long-standing debate among penguin scientists.

Flipper bands have been used for decades because they can be read at a distance by researchers using binoculars. This means that the penguins do not have to be recaptured, which would be stressful for the birds. But some scientists have questioned whether the bands harm the penguins' health, perhaps by damaging their flippers, or causing a drag effect on the flippers that means the penguins have to use more energy when swimming and fishing.

To look at the long-term effects of flipper banding, scientists from French and Norwegian universities conducted a decade-long study of king penguins on the subantarctic Possession Island in the Southern Ocean. They implanted tiny electronic tags under the skin of 100 penguins, and then fitted half of those birds with flipper bands. Antennas buried along the penguins' pathways between the colony and the sea allowed the scientists to identify the individual birds by radio frequencies and monitor them as they left and returned to the colony.

Over the 10-year period, the banded birds had a 16% lower survival rate and produced 39% fewer chicks than non-banded birds. Not only that, but the banded birds arrived later at their breeding sites, and continued to have a delayed breeding cycle on account of their longer food foraging trips, refuting the theory that penguins get accustomed to their bands after a certain time.

Given that many scientists view penguins as "sentinel species" that are likely to show the first effects of climate change, another important result was that the banded penguins did not react in the same way as the non-banded birds to changes in sea temperature.

"In favourable periods, when the sea temperature is low and food resources are abundant, there is virtually no difference between banded and non-banded animals," said Claire Saraux of Université de Strasbourg, one of the authors of the study.

"On the other hand, when the sea temperature is higher, the penguins need to forage further to find their food and banded birds then stay longer at sea."

Not everyone agrees that these results can be generalised to all penguin species and all flipper bands, however. World-renowned University of Washington penguin biologist Dee Boersma, who has used bands to study Magellanic penguins in Argentina, told NPR that she has no doubt the Possession Island study "shows that the bands that they used on king penguins harmed the king penguins ... But all bands are not created equal. It depends on what material that they are made of, it depends on how they are shaped, it depends on how they are fitted to the individual penguin. It depends on what penguin species it is."

University of Bristol's Peter Barham is the lead scientist on an Earthwatch project studying African penguins on Robben Island in South Africa. Commenting on the Possession Island study, he said, "There have been several studies on the effect of banding on African penguins and Magellanic penguins which have been unable to find any significant differences between banded and unbanded penguins when it comes to breeding success.

"There are, however, other impacts of banding which is one reason why we want to introduce [a] recognition system to replace banding where possible. From time to time, for example, we find African penguins trapped by their bands."

This is an important point: if the use of bands is to be discontinued, alternatives must be found. The electronic tags used in the king penguin study have the disadvantage that they cannot be read at a distance; the penguins must come into close proximity with the antenna that "reads" the bird's identity. Barham and the Earthwatch project team are testing and refining an automatic recognition system that will recognise the patterns of spots on individual adult African penguins' chests, allowing them to monitor the penguins remotely. A remarkable system, but it will only work for penguin species that have individual markings - and not all do.

In the meantime it is likely many penguin scientists will keep using flipper banding. And as current knowledge of the effect of climate change on penguin populations is based to a large extent on data from banded birds, the Possession Island study's authors say such information should be viewed with caution. 

Sources
Band of Bothers by Daniel Cressey, 12 January 2011, Nature News
Flipper bands can harm king penguin population by Christopher Joyce, 12 January 2011, NPR
New technology will help to protect South African penguins, Bristol University press release, 14 January 2011, University of Bristol
Southern hemisphere territories: flipper bands hinder king penguins, CRNS news release, 14 January 2011, AlphaGalileo
Unethical flipper bands are damaging to penguins by Richard Black, 12 January 2011, BBC News

Nature article citation
Reliability of flipper-banded penguins as indicators of climate change. Claire Saraux, Céline Le Bohec, Joël M. Durant, Vincent A. Viblanc, Michel Gauthier-Clerc, David Beaune, Young-Hyang Park, Nigel G. Yoccoz, Nils C. Stenseth & Yvon Le Maho. Nature. 13 January 2011

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