Same Oceans, Similar Prey, Two Very Different Necks

Same Oceans, Similar Prey, Two Very Different Necks

It was a question that dogged biologists, Agustina Gómez-Laich recalls: Why the neck?

Imperial cormorants, lanky, long-necked creatures that live on the southern coasts of Argentina and Chile, spend much of their time immersed in the frigid waters of the ocean. They dive to chilly depths — in the colony Dr. Gómez-Laich studies, up to 80 meters, or 240 feet — to hunt fish.

But the cormorants have neighbors: Magellanic penguins. Their stout, well-insulated bodies seem like a much better choice for hunting in this unforgiving environment, while the slender, exposed necks of cormorants are like gloveless hands in January.

“They would lose heat,” says Dr. Gómez-Laich, who is a researcher at the Instituto de Biologia de Organismos Marinos in Argentina. “So what’s the advantage?”

As it turns out, she and her colleagues have found that long, flexible necks offer real benefits when you hunt like a cormorant, according to a paper just published in Proceedings of the Royal Society B. While cormorants shed heat in the ocean, this energy loss may be offset by being able to move only their head, not their whole body, when they snap up prey.

The team mounted two accelerometers, which record movement, on each bird’s head and body. Then they let the penguins and cormorants go hunting, collecting data on how they moved over the course of each dive.

Penguins spot their prey from far away and swoop in at high speed before the fish can react. Their heads and bodies move together, the researchers saw.

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