emperor penguins

Physical characteristics

Adults average about 0.75 metres (2 ft 9 in) and weigh 30 kilograms (75 lb) or more. The largest individual was about 46 kg (102 lbs.). The head and wings are black, the abdomen white, back bluish grey, and the bill is purplish pink. On the sides of the neck, there are two golden circular stripes.

Like the King Penguin counterpart, a male Emperor Penguin has an abdominal fold, the "brood pouch", between its legs and lower abdomen.

The Emperor penguin has a thick coat of feathers that insulate the entire body, excluding only the legs.

Emperor penguin chicks are covered with a thick layer of light gray down. This covering ensures that they retain as much heat as possible, vital at this early stage when they are not capable of maintaining their body temperature. In addition, the infant emperor penguin's orbital area is covered in white downy feathers, unlike the all-black feathered head of the adult.

A distinguishing characteristic between males and females is their call.

Ecology and behavior

Emperor Penguins are social animals, both foraging and nesting in groups. In severe weather the penguins huddle together for protection. They may be active day or night. Sexually mature adults travel throughout most of the year between the nesting area and foraging areas in the ocean. From January to March, Emperor Penguins disperse into the oceans, traveling and foraging in groups.

These penguins can dive 150 to 250 meters (490-820 feet) into the Southern Ocean. They can venture deeper, the deepest diving on record being 565 m (1870 ft). The longest they can hold their breath when underwater is 20 minutes. Their swimming speed is 6 km to 9 km per hour (4-6 mph), but they can achieve up to 19 km per hour (12 mph) in short bursts. One of their feeding strategies is to dive to about 50 meters, where they can easily spot sub-ice fish Pagothenia borchgrevinki swimming against the under surface of the sea-ice, which they then catch, dive again and repeat the sequence about half a dozen times before surfacing to breathe.

On land they alternate between walking with a wobbling gait and sliding over the ice on their bellies, propelled by their feet and their flipper-like wings. During the beginning of the Antarctic winter, in March and April, all mature Emperor penguins travel to colonial nesting areas, often walking 50 to 120 km from the edge of the pack ice.

In response to the cold, emperor penguins stand in compact huddles ranging in size between ten and many hundreds of birds, each leaning forward on a neighbor. Those on the outside tend to face inward and push slowly forward. This produces a slow churning action, giving each bird a turn on the inside.

In the wild, Penguin predators include Antarctic giant petrels (Macronectes giganteus), Leopard seals, orca, skua, and sharks. Abandoned sled dogs and their progeny formerly preyed upon penguins before the removal of dogs from Antarctica.

Reproduction

Emperor Penguins first begin to breed at approximately five years of age. Emperor penguins travel about 90 km inland to reach the breeding site. In March or April, the penguins start courtship, when the temperature can be as low as -40 °C (-40 °F). Emperor penguins are serially monogamous. They have only one mate each year, and keep faithfully to that one other penguin, but each year, most choose different mates. In May or June, the female penguin lays one 450 gram (1 lb) egg, but at this point her nutritional reserves are exhausted and she must immediately return to the sea to feed. Very carefully, she transfers the egg to the male penguin, who will incubate the egg in his brood pouch for about 65 days consecutively without food by surviving on his fat reserves and spending the majority of the time sleeping to conserve energy. To survive the cold and wind (up to 200 km per hour, or 120 mph), the males huddle together, taking turns in the middle of the huddle. If the chick hatches before the mother's return, the father sits the chick on his feet and covers it with his pouch, feeding it a white milky substance produced by a gland in his esophagus.

After about two months, the female returns. She finds her mate among the hundreds of fathers via his call and takes over caring for the chick, feeding it by regurgitating the food that she has stored in her stomach. The male then leaves to take his turn at sea. His trip will be slightly shorter than before, because the melting of ice in the summer will gradually decrease the distance between the breeding site and the open sea. After another few weeks, the male returns and both parents tend to the chick by keeping it off the ice and feeding it food from their stomachs. About two months after the egg hatches, as the weather becomes milder, the chicks huddle in a crèche for warmth and protection, still fed by their parents using the food from their stomachs.

Eventually, both child and parents will return to the sea and spend the rest of the summer there to feed. At the end of the summer the whole inland trip will repeat itself, and all penguins at approximately five years or older will participate to breed, while the younger ones stay at sea until they are old enough.

Morphology of the skeleton

View 3D computed tomographic (CT) animations of the emperor penguin skeleton (juvenile and adult) at DigiMorph.org

Conservation status

Estimates of the Emperor penguin population range from 150,000—200,000 breeding pairs.[1] The species is considered stable.

Miscellaneous

• In early and mid-20th century, the penguins were hunted for their fat.
• In 1993, the Emperor penguin was featured in the BBC nature documentary series Life in the Freezer hosted by David Attenborough
• In 2005, the Emperor penguin was featured in the documentary film March of the Penguins.

Further reading

• Deguine, Jean-Claude. 1974. Emperor Penguin: Bird of the Antarctic. The Stephen Greene Press, Vermont.
• Rivolier, Jean. 1956. Emperor Penguins. Elek Books, London.
• Williams, T. (1995). The Penguins. Oxford, England: Oxford University Press.
• (1997) “Emperor Penguin”, Great Book of Birds. Philadelphia: Courage Books.
• National Geographic CritterCAM additional feature on DVD version of March of the Penguins

References

• BirdLife International (2004). Aptenodytes forsteri. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern

External links

• University of Michigan info site with citations for specific studies
• Info on Emperor Penguins by 70South
• National Geographic Kids' Creature Feature: Emperor Penguins
• Photographs of Emperor penguins
• The Emperor Penguin: Aptenodytes forsteriis
• Information about penguins
• Morphology of the Emperor Penguin including 3D computed tomographic (CT) animations of skeletons
• Emperor Penguin videos on the Internet Bird Collection
• Penguin World: Emperor penguin
• Emperor penguin (Aptenodytes forsteri) facts - Wild Animals Online encyclopedia