Emperor Penguins: Uniquely Armed for Antarctica
National Geographic Channel
|March 29, 2004|
During the Antarctic winter the South Pole becomes the coldest place on
the planet. Temperatures regularly plummet to minus 60° Fahrenheit
(minus 50° Celsius), prompting most of the 9,000 species of birds
that cross the continent to hightail it for warmer climes.
Only one birdthe emperor penguinwill winter on Antarctica and use the frozen continent as a nursery. When the winds really start howling, the birds march inland by the thousands, creating 40 or so breeding colonies on the sea ice along the edge of the continent.
"This is an animal that does things in extremes," said Paul Ponganis, a research physiologist at the Scripps Institute of Oceanography in San Diego. Ponganis has studied penguins for over a decade. "Emperors can fast for extreme amounts of time and dive to extreme depths, which allows them to live in a very extreme place."
Emperor penguins are veritable sea bulletsthey can zoom to a depth of 1,500 feet (500 meters) to feed, holding their breath for as long as 22 minutes. That allows the penguins to exploit resources other birds can't.
Working from his gale-proof base at the McMurdo Station on Ross Island, just off the Antarctic continent, Ponganis tags along on some of the penguins' dives by corralling a few of them and attaching miniature video recorders to their backs. Other bite-sized gadgets measure the penguin's oxygen levels, heartbeat, and temperature.
"Penguins are as well designed for underwater flight as birds are for flying in the air," Ponganis said. "And when they swim, they really are flying underwater. A penguin's wings act the same while it's swimming as a bird's does while it's flying."
However, a penguin's strokes are even more efficient. "Emperors can exert propulsion on both the upstroke and downstroke, while most other birds only exert pressure on the downstroke [during flight]," said David Ainley, an ecologist at H.T. Harvey and Associates, a biological consulting firm in San Jose, California. Ainley has studied Antarctic birds for over 20 years.
Long glides to the surface probably help emperor penguins conserve energy during their deepest dives. Another key is their solid bones. While skybound birds have evolved hollow bones to lighten their weight, penguins gradually lost that internal airspacedecreasing their buoyancy so they can plumb the depths.
Even then, emperor penguins never get wet.
Their outer feathers are flat, well oiled, and watertight. There is an air space between those feathers and the bird's skin that water never penetrates, keeping them from turning into icicles in the black Antarctic sea. "They have the highest feather density of any bird, about a hundred feathers per square inch (6.5 square centimeters)," Ainley said.
Life in the Icebox
The sun disappears completely once winter falls in Antarctica in early May. The only light comes from the moon, circling just above the horizon. That's when emperor penguins move onto the ice. Their airtight feathers will become ever more crucial as winter howls around them.
Scientists bundle up in giant parkas and goggles to keep an eye on goings-on. Giant PistenBully machinesvehicles with tank-like treads that are often used to maintain ski slopesallow them to motor around on the sea ice and fit penguins with gizmos to measure the animals' vital statistics.
"Underneath their feathers, it can be 30° to 35° Celsius [86° to 95° Fahrenheit], while the outside air is minus 20° or minus 30° Celsius [minus 4° or minus 22° Fahrenheit]," Ponganis said. "That's more than a 60° temperature difference separated by a layer of feathers that is maybe a half an inch (one centimeter) thick."
That astonishing insulation is critical because not only do emperor penguins rear their young in the extreme Antarctic environmentthey do it while fasting. Once they hit the ice, there will be no opportunity to feed.
Within a matter of weeks, the female lays her egg and passes it off to the male, allowing her to head for the sea to feed. The male promptly tucks the egg into a small pouch over his feet. He will balance it there until it hatches. Inside the pouch, the egg is kept at a toasty 95° Fahrenheit (35° Celsius) the average body temperature of an adult.
Rarely moving, never eating, standing in frigid cold, the fathers-to-be will lose half their body weight incubating their egg over the next two months.
The key to surviving this impossible feat is the huddle.
Birds of a Feather
Most male penguins are known for being obstreperous, territorial squawkers. Not emperor penguins. They huddle in tight knit groups that can number in the thousands while tending their eggs.
The largest colony is on Coulman Island in the Ross Sea, where as many as 25,000 males hunker down.
Huddling keeps them warm. There can be a 20° to 30° temperature difference between ambient air inside the huddle compared to the shrieking cold outside it. Since the animals don't have to work as hard to stay warm, their metabolism slows down and they burn less fat. As a result, their ability to survive the fast increases.
Infancy in a Shrieking Gale
Although scientists like Ponganis and Ainley have discovered much about how the birds thrive in this harsh climate, that doesn't answer the question of why they choose to raise their young during the raging Antarctic winter.
"The reason that they do it is for the stability of sea ice. They are breeding and rearing their young on ice that will melt come summer," Ponganis said. "Starting in January, their colony sites will begin breaking up into open ocean." Once the chick is born around early August, the mother returns from feeding at sea to give dad a break. For the next five months, he and his partner will take turns regurgitating fish and squid to the chick.
Once the sun starts heating up the water and the ice begins to dissipate, the emperors leave their chicks, forcing them to fend for themselves for the first time.
"December is the start of the Antarctic summer, when food is most available, thus making it as easy as possible for their chicks to forage," Ainley said.
As the ocean swells start tearing apart the ice, the young chicks become increasingly agitated. Once it's clear their parents are not returning, usually in the first week of January, the chicks head from a world of collapsing white into a dark and frigid sea.
For their parents, a few months of gorging begins in preparation for the following May, when the ritual of rearing young in the most forbidding climate on Earth begins anew.
For more on penguins, tune in to this week's Living Wild. The show airs Tuesday, March 30, at 8 p.m. ET/PT in the United States and is available only on the National Geographic Channel.
Got a high-speed connection? Watch Living Wild video clips in streaming video.
Creature Features: Emperor Penguins
Ice Buildup Hampers Penguin Breeding in Antarctica
Patagonia Penguins Make a Comeback
Related Web Sites
National Geographic Channel
Be The CreatureExplore A Creature!
Penguin Files: Penguin Researchers in the Ross Sea, Antarctica
U.S. Antarctic Program
|© 1996-2008 National Geographic Society. All rights reserved.|