King and Emperor penguins, for instance, have been known to cover almost 1,000 miles on foraging trips that last up to a month, swimming more than 40 miles per day. Adelie penguins are believed to swim up to 3,000 miles to return to their spring nesting grounds, having spent the rest of the year roaming the drifting pack ice around Antarctica. Later, more sophisticated devices recorded Emperors staying underwater for up to 11 minutes and diving to at least 1,766 feet. The devices showed that other penguins also ventured into deep waters far more often than biologists had thought possible. Researchers observed one Gentoo penguin, for instance, making more than 450 dives in 15 hours, some to lower than 300 feet.
Penguins excel at underwater diving.
At 1,200 feet, for instance, the birds are being squashed by 40 times the pressure they feel at the surface. The big squeeze is dangerous because it crushes the air in the penguin's lungs to just one-fortieth of its original volume, making it hard for oxygen to circulate to the brain and other vital organs. This not only allows the birds to hold their breaths longer, but also reduces the risk that their blood will become contaminated by nitrogen, researchers say. Whether the penguins can consciously control or limit this body shutdown, or whether it occurs automatically when they reach certain depths, is not yet known. Penguins also have other adaptations that make them highly efficient menaces of the deep sea.