Though ungainly on land, the flightless penguin has physical characteristics perfect for swimming through water – fortunate, as some species are known to be at sea for up to 75 per cent of their lives. Spending so much time in the water puts penguins at risk from predators, so swimming skills are essential. While their long, streamlined bodies and short legs give them a clumsy gait when waddling on land, penguins’ wings have a unique characteristic that gives them surprising agility in water.
While penguins’ wings are not suitable for aerial flight – mainly because, unlike the delicate lightweight bones of other birds, penguin bones are solid – they are perfect for soaring through water, with the Gentoo penguin reaching speeds up to 35km/h (22mph). Referred to as flippers, the penguin’s stiff wings act as the perfect natural paddle. What’s most interesting, however, is the recent discovery that as well as being able to flap their flippers up and down like wings, penguins can also twist them in a corkscrewing motion.
The joint attaching the flipper to the body is similar to that of a human shoulder, enabling the bird to better control its movements and speed. A swimming penguin can rotate one flipper in one direction and the other in another, enabling it to turn instantly or stop suddenly. Twisting causes a greater surface area of the wing to move over the water, which generates a greater thrusting force so the penguin can increase its speed without the need for more flapping.
Another technique the penguin uses for moving through water is porpoising. Whenever it needs to breathe, the penguin will periodically swim fast under the water and then use its flippers to leap from the water in an arc. The momentum of porpoising helps penguins when they need to flee quickly from predators.
The humble penguin is one of the planet’s best-equipped swimmers and the ‘twisting flipper’ motion is currently being applied by scientists who are looking to develop robot technology that helps to improve the efficiency and performance of underwater vehicles.