There are 18 different species of penguins, and they vary in size and shape. The emperor penguin is the largest of all living penguins, standing at 4 feet and weighing 90 pounds. The smallest of the penguins is the little blue penguin, standing just 10 inches and weighing about 2.5 pounds.
Everything about a penguin is fine-tuned for swimming. Their body is rounded in the middle and pointed at either end, which is the perfect shape for sliding through water. Their powerful, flipper-like wings propel them through the ocean. Penguins are awkward on land, but their short legs and webbed feet are the perfect rudder system underwater. And unlike other birds, penguins have solid bones. This added weight counteracts their natural buoyancy and helps them move quickly through water.
Penguins use their torpedo-shaped body to shoot through water at speeds of 15 miles per hour or more. Some penguins leap into the air while swimming—a trick known as porpoising.
Penguin legs are short and strong. Their feet are webbed, with visible claws. Penguins walk with short steps or hops, sometimes using their bills or tails to assist themselves on steep climbs. Some species, like the rockhopper, jump from rock to rock. Antarctic species can move much faster over ice by “tobogganing” on their bellies, using their flippers and feet to help them move along.
Their tuxedo-like black and white coloring is extremely effective camouflage—known as countershading—which helps them hide from predators and prey in the open ocean. For example, if a shark or other predator swims below a penguin, the penguin’s white belly blends in with the bright sunlight coming from above. Likewise, if a penguin swims below some fish it wants to catch, its black back blends in with the dark depths of the sea.
Different species of penguins can be identified by their head and facial markings. Penguins only eat seafood and swallow their food whole since they don’t have teeth. They use their powerful, hooked beaks to catch fish, squid and krill. Their tongues have a rough, Velcro-like texture that helps them hold and swallow their slippery food. The New England Aquarium’s 65 penguins eat nearly 600 pounds of sardine, capelin, smelt and herring every month. Most of them eat five to ten fishes every day.
Like many animals, penguins have a nictitating membrane, sometimes called a third eyelid. This is a clear covering that protects the eye from injury.
A penguin’s tail is short and wedge-shaped. Adelie, gentoo and chinstrap penguins (known as brush-tailed penguins) have 14 to 18 stiff tail feathers, which they often use as a prop when on land.
Penguins have about 80 feathers per square inch—more than any other bird. Penguins need all of those feathers to keep warm and dry. The fluffy down at the base of each feather traps air near the penguin’s skin. This air layer helps penguins keep warm, even in cold air and frigid water. When penguins are too warm, they fluff their feathers to release extra body heat.
The outer tip of each feather is stiff and small. Every feather tip overlaps with those around it, like shingles on a roof. This is what keeps penguins dry in the ocean. The tips of the feathers get wet, but the fluffy down stays dry and warm. Penguins replace their feathers, or molt, once a year. Every year during a two to threeweek period, they shed their feathers and grow a complete new set. This means penguins have to keep their feathers healthy for a whole year. Because of this, most penguins spend hours every day taking care of their feathers, a behavior known as grooming or preening. A grooming penguin first cleans each feather, removing dirt and water. Then it conditions the feathers by spreading out oil from a gland at the base of its tail.
Penguins are vulnerable to predators and cold temperatures during molting. The old feathers are no longer waterproof or insulating and the bird cannot enter the ocean to catch food or to escape land predators. Because penguins fast during the molting period, they must gorge themselves for a few weeks prior to
molting. They live off stored fat until new feathers grow in.
As in most birds, penguin hearing is thought to be good. Vocalizations (calls) are important in communication and mate recognition. Penguins have good vision both on land and under water, since they can change the shape of their cornea. The sense of taste in penguins has not been extensively studied. In general, the sense of taste is poorly developed in birds. Penguins’ sense of smell may be more developed than early studies indicated since the olfactory lobe of a penguin’s brain is large.