Emperor Penguin ~ Aptenodytes forsteri
All photos copyright Freezingpictures/Jan Will unless otherwise noted. Used by permission.
Sleek and elegant, the emperor penguin belongs to a family of misfits. In a world where land, water, and air host their own unique inhabitants, like foxes and fish and eagles, penguins don't seem to belong. Their stunted wings don't allow them to fly; their bumbling gait hardly allows them to run. They can hold their breath underwater for only a few short minutes. The world record is eighteen.
Are penguins are the survivors of an evolutionary spoof, a failed experiment of Nature that left them struggling to survive on an unforgiving planet? After getting to know these silly birds, one has to say, "Hardly." Penguins have talents you might never have imagined.
Covering the stumpy body of a penguin is a layer of tiny feathers, denser than in any other bird at 80 per square inch, oiled and overlapped to repel water and insulate. These feathers are normally shades of black or white, and some penguin species have patches of orange on their necks and heads (such as the emperors and kings) or "crests" (such as on macaroni penguins), small yellow plumes that curl backward from above the bird's eyes, like a punky hairdo. Penguin beaks are shaped a bit different in each species and are specialized for catching a diet of seafood like krill, amphipods, and small fish. A penguin's webbed feet--spiked with large toenails to grab icy surfaces--are positioned far back on its body, forcing the animal to stand and walk upright, balanced on the soles of its feet, instead of bent forward like most other birds. All these characteristics have fueled the penguin's popular image as a stiff waiter in a tux, lovable, reserved and slightly self-conscious. With so much popularity, isn't it a shame there aren't any penguins in the North? They are only found near the equator and south of it, normally on islands that experience freezing, harsh winters.
Two things that go along with most penguins: cold weather and water. In fact it seems they were made for them.
Although a few penguins living at the equator on the Galapagos Islands cope with warm weather well enough, they are the exception. Penguins are especially suited to retain heat. Warm-blooded, they must maintain temperatures of between 95 and 105.8 degrees Fahrenheit, not an easy feat during, say, a blizzard with continual below-zero wind gusts. Normally, just breathing the biting air would cause tremendous heat loss, but the penguin's nasal passages are lined with a mucous membrane that warms incoming air and absorbs heat from outgoing air, an efficient process that also condenses humidity and prevents dehydration. Another physiological feature called a "countercurrent heat exchange" system allows warm, arterial blood from the penguin's heart to transfer heat to the cool venous blood returning from the chilled extremities. (In warmer weather penguins' bodies bypass this system, routing more blood through the wings where heat can escape; then the birds fluff themselves up and pant.) Penguin feathers, besides keeping the birds waterproof, also trap air next to their skin, creating a sheath of insulation. Like all birds, penguins regularly preen and oil their feathers (the oil is produced by the uropygeal gland near the tail), but even so they molt once a year, replacing old and worn out feathers with fresh, new ones. During a molt a penguin is not waterproof and must stay onshore, so it eats an extra amount of food during its dives before and after the molting season. Luckily, penguins quickly store up the extra food they eat in the form of body fat, reserving it for periods when the bird must fast for weeks or months, and in the meantime the fat keeps them warm. If all else fails, penguins act like you and me: They shiver.
But as well as they fare against the bitter winds of snow-blown slopes, it is in water that penguins truly dazzle. Their status as birds serves only to mislead us from their prowess beneath the waves.
It comes as a surprise to many people that some penguin species spend three quarters of their lives in the ocean, long enough for barnacles to attach to their tales! Some spend weeks at sea, feeding voraciously and traveling hundreds of miles. No other birds can dive as deep or as long as penguins. Most penguin species can dive 300 feet and remain submerged for five minutes, but the husky emperors hold all records for distance, depth and duration--950 miles, 1752 feet, and 18 minutes (though not all on the same dive). The key to these Olympic abilities lies in design. The penguin's body is shaped like a torpedo, and slices through the sea with as much agility as an eagle in the air. In this new environment we realize that the penguin's feather-coated "wings" are not wings at all. They are flippers. Rather than creating lift, the penguin's flippers propel them forward, using both upstroke and downstroke. Fused bones make the flippers stiff, giving the penguin such maneuverability that it can change directions underwater instantly. Feet and tail are rudders. Penguins really can fly--they fly underwater.
Penguins have three modes of swimming: diving, porpoising, and travel diving. During a normal dive, a penguin plunges into the ocean, down and then back up, in the form of a V, or down and forward and up, like a U. In the process the penguin will be shooting out its S-shaped neck toward various munchies--cephalopods, crustaceans, fish. The black and white tuxedo penguins wear may also help them catch prey and avoid predators such as leopard seals and sea lions. In an effect called countershading, the penguin's black back makes it nearly invisible against the dark sea floor, while from below the bird's white stomach blends perfectly with the brightness of the surface. And by swimming upside-down, it is thought that penguins can use their bellies to reflect sunlight onto schools of fish above them, illuminating them like bright little snacks. Although penguins always catch each piece of food individually, they may catch several dozen organisms in a single dive. Even the penguin's tongue is specialized for underwater eating. Small spines on the tongue and upper throat prevent squirmy prey from beating a hysterical retreat. Penguin lungs are super-efficient at extracting as much oxygen as possible from every breath, but after a few minutes of heavy feeding the penguin must return to the surface for air and rest.
The second mode of swimming is porpoising--accelerating underwater and leaping through the surface like dolphins. This activity throws off predators, so penguins often porpoise while traveling near shore, where their enemies are most likely to lurk. Once a few miles from land, penguins switch to the third mode, travel diving, composed of shallow dives just a couple minutes long, and half-minute rests on the surface, where the penguin paddles along like a duck. Underwater swimming is the fastest (10 mph for emperors) and most efficient. In fact penguins consume one-third less energy traveling underwater than traveling on land. Beside their body shape, a factor that helps penguins swim underwater so effortlessly is the density of their bones. While most birds have bones with tiny air pockets to lighten them, penguin bones are heavier, making it easier for the animal to remain submerged. Dense bones also store less nitrogen, which can make deep diving hazardous.
You might have noticed by now that the multiple penguin species (17 of them) are quite distinct, each with different looks, habits and abilities. Some swim long distances to sea, others stay close to shore. Some are large, like the 75-pound-or-more emperors and kings, while others are very small, like the appropriately named little penguin, at 2.25 pounds. Some species are more vocal than others. Some lay only one egg, others lay two. Rockhopper penguins have a distinct strategy for climbing rocks--and you guessed it, they hop. Emperors penguins, specifically, are unique for their size and record-setting swimming abilities. But even more unique are their breeding habits, which take them on a much-celebrated journey over miles of ice and snow, through hunger, dangers and blizzards, on the coldest continent on earth. All to raise a chick.
During March and April, Emperor breeding season begins. Members of the species who are at least three years old leave the shore and begin a long trudge inland toward their colony's breeding ground, where they have met to select a mate and raise chicks year after year. The adults, both males and females, have been gorging themselves of late, building up body fat for the event at hand. On average, males now weigh 83.6 pounds, females, 63.8 pounds. Waddling along at less than one mile an hour, these penguins make use of an exciting traveling technique: On slopes they flop on their bellies and toboggan, pushing with their feet. This saves much-needed energy for the trek ahead of them--in some cases 70 miles.
Once at the breeding site, thousands of males and females start in with a racket: "Ah-ah-ah-ah!" Spreading their flippers, they rub their beaks on their underarms, then bow their heads and make their call. "Ah-ah-ah-ah!" Each penguin's voice is slightly different than his neighbor's, like a fingerprint, and penguins within 23 feet of one another take turns, so that their calls do not overlap. Once a female chooses a male from among the loud mass, a complicated and drawn out courtship ritual begins. First they simply stand together and make their calls in harmony--important because they will need to be able to recognize each other's voice in later months. After this, the duo marches in line together, the female leading. Finally they bow to one another several times, until at last the female lays on her stomach, and the male mounts and mates with her.
Come May, the female lays a single egg, about the size of a man's hand. She literally gives birth on her feet, balancing the egg on her toes and immediately blanketing it in cozy folds of abdominal skin. Though successful, this new mom hasn't eaten anything for about 40 days, and the development and laying of the egg has taken all her spare energy. She must return to shore immediately to eat. Dad, although he hasn't eaten either, gets the job of incubation--the monotonous task of egg warming that is shared between the parents in other penguin species. So, before they part, the emperor couple must accomplish a tricky move, in which the female must pass the egg to her mate. In the subzero temperatures of Antarctica the egg cannot touch ice (i.e. the ground) for more than a few seconds, or the developing chick inside will die. Sometimes the male fumbles in his egg cradling attempt. In only a few moments, he has lost he and his mate's only chance of offspring that year.
Other couples make their egg pass without a hitch, and part company quickly. The female returns to water, while in the face of the oncoming Antarctic winter the male stays behind at the breeding ground to care for his egg. As the earth circles the sun during a U.S. summer, the South Pole dips away into perpetual shadow, and Antarctica is plunged into 24-hour night. Temperatures drop and blizzards set in, driving stinging snow and winds of over 100 miles per hour and -80 degrees F. Yet in spite of this, the egg, resting on its father's feet, is a balmy 88 degrees, warmed by folds of penguin skin and feathers. The male is constantly active, rotating the egg every twenty minutes or so, presumably to keep it uniformly warm. Not only this, he is part of a giant mass, a slowly moving "huddle" of thousands of male penguins keeping close to stay warm. As the huddle moves, penguins in the center of the group move out to the front, taking a turn in the windy section, and in the process giving everyone time to warm up in the center. In this way huddled Emperors lose only half the energy they would if they were alone. For two months the males fast, endure the dark and cold, and keep their eggs alive.
At about day 62 or so after laying, a hole breaks through the egg shell, giving way to the beak of a young chick. It has survived. It exits its shell while remaining on its father's feet, and hopes for food. But the father's stomach has long been empty, and the mother may not have returned from shore yet. Amazingly, a special gland in the father's throat produces a milky meal for just such a predicament. It tides the chick over for a few more days until Mother arrives.
Molting chick. Photo courtesy NOAA/Michael Van Woert
And how welcome she is! The males have now fasted for over a hundred days, and have lost about 30 pounds off their original 83-pound average; they are eager to get back to the ocean and its food. When the females arrive, they must be able to remember and identify their mate's signature call among thousands of others. Once reunited, Mom takes over the chick, regurgitating luscious meals of seafood for the growing baby. --Unhappily, a few mothers will find that their egg or chick has been lost, bumped out of her mate's grip or simply not strong enough to make it until her return. Or, the mother will not have returned at all, forcing the undernourished male to make for shore himself, to the demise of the chick.
But for multitudes of other families, all goes well. The male returns to the breeding grounds after 24 days, once again allowing the female to return to shore, which, incidentally, moves closer and closer as the ice shelf breaks up under spring's heat. Soon both parents work to feed the chick, which by a little over a month after hatching has grown enough to endure the cold on its own. After their first molt in early November, the chicks can take to water themselves. From this point on, they must survive in the clutch of a wild, blue sea. Which is what they were born for. ~GL~
- Taxonomy: Kingdom Animalia; Phylum Chordata; Class Aves; Order Sphenisciformes; Family Spheniscidae; Genus Aptenodytes; Species Aptenodytes forsteri
- Status: Emperors are found in Antarctica, Argentina, Chile, Falkland Islands (Malvinas), French Southern Territories, Heard Island and McDonald Islands, New Zealand, South Georgia and the South Sandwich Islands. They are one of only four penguin species that breed in Antarctica. According to the 2004 IUCN Red List, the 270,000–350,000 Emperor Penguin population is stable and not threatened.
- Links: Luc Jacquet's March of the Penguins (Official Film Site) ~ Emperor Penguin Skull (DigiMorph) ~ Guillaume Dargaud's Penguin Page ~ National Geographic's Emperor Penguin Creature Feature ~ Pete & Barb's Penguin FAQ ~ Icetrek Photos
This Biofile was written by Daniel James Devine.