Wednesday, 4 April 2007

Happy feet hit treadmills to track climate change

They may not be able to tap dance, but king penguins in the Antarctic could in fact have a role in monitoring the effects of climate change, new research suggests.

Scientists have long studied our changing environment in terms of unusual animal behaviour, such as altering patterns of fish and bird migration. Now, a research team from the University of Birmingham is finding out if the energy requirements of king penguins could be used as an alternative bio-indicator to monitor the health of the environment.

King penguins predominantly feed on a variety of fish called myctophid fish, explained bioscientist Lewis Halsey, who led the research on Possession Island in the South Indian Ocean. As the Southern Oceans warm, these fish tend to migrate further South, and away from the Islands inhabited by king penguins, he said, which makes hunting more difficult for the penguins.

“As the king penguins have to work harder to forage for the fish, their energy expenditure in doing so will increase,” Halsey said. “[This tells] us that the myctophid fish are changing location and becoming more sparse in areas of the Southern Oceans where king penguins forage.”

King Penguin - Lewis Halsey
King penguins are good candidates as bio-indicators for several reasons, the researchers say. Firstly, while at sea foraging, they cover hundreds of kilometres and are able to dive to depths of several hundred metres, so they explore a relatively large portion of the expansive Southern Oceans. Secondly, the diets of several populations of king penguins are well known. Thirdly, while foraging for food is done at sea the penguins also come ashore to breed and moult, making them accessible to researchers.

To ascertain the penguins’ energy requirements, researchers have implanted miniature heart rate data loggers into the birds. The penguins’ heart rates are then collaborated against energy expenditure under laboratory conditions, by getting the penguins to walk on a treadmill at different speeds. This data provides a correlation between heart rate and rate of energy expenditure, so any heart rate data subsequently obtained when the king penguins go to sea to forage can be used to estimate energy expenditure.

“We have deployed these loggers on birds for several years so we can look to see if the energy expended by king penguins from year to year is changing, which may give us information on the availability of myctophid fish in the Southern Oceans each year,” Halsey said.

More data is needed from the heart rate loggers during the next few years before any long term trends can be established. If the energy expended by king penguins at sea increases over time, it is likely that myctophid fish are getting harder to come by, which could be due to the warming of the Southern Oceans, Helsey said.

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