Humpback Whales Linger in Antarctica Long into Autumn

By Chelsea Whyte on July 31, 2012 4:52 PM EDT

humpback whale
Humpback whales find more to feast on during the autumn due to changing climates and receding sea ice. (Photo: Creative Commons: Fritz Geller)

In the southern  hemisphere, winter is in full swing, which usually means that humpback whales have headed toward warmer waters. But new research shows that these large mammals are lingering in Antarctic bays to feast on krill long after scientists thought their migrations to distant breeding grounds would begin.

The krill are available later in the season than usual due to a reduced extent of sea ice, reports Mongabay News. The study suggests that climate change is affecting the food chain, and also finds that inland channels are more important food sources for whales than previously thought.

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"The old dogma is that by late autumn, the ice is heading in and the whales have headed out," said study author David W. Johnston, a research scientist at Duke's Nicholas School of the Environment.

"But 70 percent of our surveying took place in waters with no ice, and we detected 371 groups of humpback whales over a 654-kilometer survey area, with density estimates of up to 1.75 whales per square kilometer."

That density rate - higher than anyone expected, researchers said - means that at any given point aboard a ship in the whale-infested waters, you would be able to see two humpbacks within 500 meters of the boat.

"We had no idea that the whales were going to be packed up in these narrow channels and passages," Johnston told MSNBC. "We had to think on our feet a bit and use alternative sampling approaches and incorporate data from other portions of the project."

Scientists have long known the waters around the Western Antarctic Peninsula are important foraging grounds for humpback whales that feed on swarms of shrimp-like krill, but previous studies have been conducted earlier in the season or in open waters farther from land.

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