Penguins Have Knees — You Just Can’t See Them

Penguins have one of the oddest body shapes of any creature in the wild. Short, stocky, and flightless, these aquatic birds spend most of their time either swimming or waddling across ice and rocks. At first glance, penguins look like they have tiny legs — or feet that simply sprout from their torso. But appearances can be deceiving. Beneath a penguin’s thick feathers and layer of fat are surprisingly long legs, complete with a femur, kneecap, fibula, and a fully functional knee joint. Most of the upper leg is simply tucked inside the body, hidden from view.

By keeping much of their legs close to their bodies, penguins maintain the streamlined profile that makes them such agile swimmers. On land, that same body plan produces their famous waddle. Many penguin species face predators at sea, including leopard seals and orcas, and as such they’re built first and foremost for life in the ocean.