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These Macaroni penguins are on their annual summer hiatus from the Subantarctic region where they breed. For the first time, scientists have tracked the movements and feeding habits of the species on its long journey, finding some surprises along the way.
updated 5/15/2009 8:56:20 PM ET 2009-05-16T00:56:20

Documentaries about penguins often show the flightless birds leaving their families and mysteriously drifting off to sea, but a new study continues the story for Subantarctic Macaroni penguins, which researchers recently spied on during a lengthy ocean adventure.

The study, published in the latest Royal Society Biology Letters, is the first to reveal the movements and feeding habits of large numbers of penguins using relatively non-invasive geolocation sensors. In the future, the technique may be applied to other penguin species, as it improves upon earlier attempts that mostly relied upon satellites.

Following ocean-bound penguins is no easy task.

"When penguins forage or travel at sea, you can just sometimes see the heads of the birds outside the sea surface, and they are very difficult to count, especially in the rough sea of the Southern Ocean," lead author Charles-Andre Bost told Discovery News.

Bost, a CNRS Chize Center of Biological Studies scientist, and his team affixed sensors onto 21 adult Macaroni penguins at Kerguelen, a South Indian Ocean Subantarctic island, during autumn. This bird is the largest consumer of marine prey among all seabirds. The scientists then re-captured the penguins the following spring and took blood samples.

The researchers found that after spring breeding, adult Macaroni penguins move quickly away from Kerguelen waters toward the east, where they spend six months swimming, diving and foraging at sea. For much of the journey, they distribute themselves widely across a narrow band within the central Indian Ocean, diving longer and to greater depths in winter than in summer.

It's not a lonely life in the ocean, however.

"Macaroni penguins usually forage in small groups," Bost explained, adding that they often call to each other and "can dive synchronously when foraging."

Previously it was thought penguins subsisted on Antarctic krill during this inter-breeding period, but the tracking and blood tests indicate the birds instead chow on Subantarctic krill and the crustacean Parathemisto gauchidaudii. During the winter months, the penguins dove deep into the water column to get their fill.

The world population of Macaroni penguins has declined over the past 20 years, so scientists are hopeful that identifying key feeding areas will lead to better conservation tactics in the future. Top marine predators, such as the Southern elephant seal, appear to favor the same central Indian Ocean feeding spot valued by the penguins.

Rory Wilson, director of Swansea University's Institute of Environmental Sustainability and the School of Environment and Society, pioneered the use of geolocators on penguins in the early 1990s.

Wilson told Discovery News he was struck by how the new approach used smooth plastic leg rings for attaching the sensors to the penguins, therefore placing "the device behind the bird, where, during swimming, drag effects are minimized."

David Gremillet, head of the CEFE-CNRS Spatial Ecology Group, called the new paper "an essential contribution to the conservation of a valuable penguin species."

"What is always striking is the vastness of the areas these aquatic athletes visit during the inter-breeding period, and remember, they cannot fly," Gremillet added. "The worrying thing, of course, is how on Earth we'll manage to protect such immense areas to ensure the conservation of Macaroni penguins."

More on  Penquins   |   Ocean life

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