| Not unlike their human counterparts, penguin legs have a femur, tibia, fibula, and knee. But unlike ours, the knees are covered by feathers — as is the rest of the upper leg, which is why penguins' legs look so adorably stubby. That appearance is most evident when the less-than-graceful birds are seen waddling on land, which is a more energy-efficient means of locomotion than it appears. They use 80% less energy than they would walking the way we do, as their movement relies on momentum and gravity to propel them forward rather than their own effort. Even so, penguins — which are collectively known as a "waddle" when on land and a "raft" when in water — are at their most elegant when swimming. An adult king penguin can hold its breath for 23 minutes and dive more than 1,000 feet deep in search of food. The animals spend up to 75% of their lives in water, which may help explain why they sometimes look like, well, a fish out of water when going about their business on land. | 
1
