I very much enjoyed this article. What struck me, however, was a passage that mentioned the “bird’s resistance to the bends” and the researchers’ alleged inability to explain that. As a scuba diver, I know that the bends, or decompression sickness, is caused by breathing compressed air underwater. More nitrogen is absorbed in body tissue per breath taken, which can cause expanding bubbles when surfacing too quickly. The bends does not occur when free diving: holding your breath and not breathing compressed air underwater. I do not believe penguins breathe underwater and am therefore confused why they’d be expected to suffer from the bends in the first place.

Bert Wissig
Kailua, Hawaii

Decompression sickness occurs in people who free dive repeatedly to great depths, researcher Paul Ponganis points out. Even-deeper penguin depths (200 meters, routinely) force nitrogen to dissolve into the body. Rapid surfacing might be expected to trigger nitrogen to form the dangerous bubbles that cause the bends .—S. Milius