Endangered Whales Dine at Dangerous Depths

Jessica Marshall - 

Endangered right whales feed at depths just below the surface where they're vulnerable to collisions with ships.

This depth corresponds to high concentrations of their copepod prey.

Ship collisions are a leading threat to this species, which numbers only between 300-400 individuals. 

Critically endangered North Atlantic right whales foraging in Cape Cod Bay in the spring spend most of their time just below the surface where they can't be seen but remain vulnerable to collisions with ships, according to a new study.

The whales appear to be following their food, because the researchers also found high levels of copepods, tiny crustaceans the size of a grain of rice, at the same depths.

"It makes sense that whales are spending time where their food is," said Susan Parks of Pennsylvania State University, lead author of the study published today in Biology Letters.

Still, the fact that the whales spent nearly all of their time just below the surface came as a surprise to the team.

"In the past I had known that right whales feed at the surface in Cape Cod Bay; you can see them swimming through the water with their head above the water and their mouth open," Parks said. "What was really surprising to me in this study was how much time the whales were spending just out of sight but at a really dangerous depth for a boat to run into them."

In fact, with the aid of trackers attached to the whales using suction cups, researchers knew that at times as many as 10 whales were within their visual range, yet they could see almost nothing at the surface. "We would know that they were right in front of us," Parks said.

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