The signature species of Antarctica -- the mascot, if you will -- is the penguin. There are not one but no fewer than 17 species of penguins, of which only four breed on the Antarctic continent itself. These include the Adelie, the Emperor, the Chinstrap and the Gentoo penguins. Several other species are sometimes found within the Antarctic region, and penguins are found as far north as the Galapagos Islands, straddling the equator. But in general, the link in the public imagination between Antarctica and penguins is supported by the numbers -- there are millions of nesting pairs of Chinstrap penguins alone, and they are by far the most numerous creatures in the region.
All penguins have a very similar torpedo-shaped body form, though they vary greatly in size. Penguin wings are highly modified to form stiff paddle-like flippers used for swimming, and their feet and stubby tails combine to form a rudder. The penguin's bones are solid and heavy, which help them to remain submerged and reduce the energy needed for diving.
Penguins are able to withstand the extreme cold because insulation provided by their short, densely-packed feathers forms a waterproof coat. A thick layer of fat or blubber also serves as an energy store. These adaptations, among others, enable them to minimize heat loss in icy cold waters so they can cope with the harsh conditions of the Antarctic. Return
BehaviorPenguins communicate by complex ritual behaviors such as head and flipper waving, calling, bowing, gesturing and preening. Territorial disputes lead to aggressive postures such as stares, pointing and even charging. Courtship and mating rituals include so called "ecstatic displays" where a bird, typically an unattached male, pumps his chest several times and, with his head stretched upwards and flippers akimbo, emits a harsh loud braying sound. This can result in a mass trumpeting by other males, which is believed to help synchronize the breeding cycle. Return
BreedingAll the Antarctic penguin species save the Emperor breed in the brief austral (southern) summer months. Mating takes place in spring for the three "brush tailed" (pygoscelid) species -- the Chinstrap, Gentoo and Adelie -- who make their nests out of rocks, bones and feathers. Adult pairs take turns incubating their eggs and feeding the chicks once they have hatched. Antarctic penguins feed mostly on fish, squid and krill, a shrimp-like crustacean which is the key species in the Antarctic ecosystem. Return
LocomotionPenguins are very efficient swimmers. Though they are comfortable at speeds around 5 mph (8 km/ph), some species can travel at 7 mph (12 km/ph) in short bursts. When traveling quickly, penguins will leap clear of the water every few feet -- an action called "porpoising" due to its resemblance to porpoise behavior. This enables them to breathe, and decreases their chances of being taken by a predator.
Antarctic penguins have also developed the ability to leap
out of the water to a substantial height on land, enabling them
to reach raised ice edges or rock ledges. Penguin legs are set
far down on their bodies, so they walk with a very erect posture.
Ashore they are often awkward, waddling and hopping over rocks;
on snow they sometimes push themselves along on their stomachs. Return
ColoniesAntarctic penguins are highly social birds which usually breed in large colonies called "rookeries". Healthy adult penguins have no predators on land, so they have no natural fear of humans. While they don't like to be approached directly, they will sometimes come quite close to a quiet observer due to their own natural curiosity. They do have predators, however: skuas and southern giant petrels will attack chicks and sick or injured adults. Return
With its white "shirt" front and white ring around its eyes, the Adelie (ah-DAY-lee) is the stereotypical penguin. They are the smallest and most widely distributed penguins in the Antarctic -- adults weigh only about 12 pounds (5.5 kg) and stand but 28 inches (71cm) high. Named after the wife of the French explorer Admiral Durmont d' Urville, the Adelie is also the most commonly studied of all the penguin species. It is estimated there are some 2.5 million pairs of Adelies around the continent. Adelie colonies form on islands, beaches and headlands all around the Antarctic coast. The presence of groups of hundreds of thousands of birds is not unusual.
Adelie penguins come ashore in October to breed during the brief weeks of summer. Mating takes place once the pair establishes a rocky nest. Older birds tend to stake nesting sites in the middle of the colony where they are better protected from marauding skuas. There is fierce competition for nesting sites, especially on the higher well-drained ground -- stealing pebbles from neighboring birds' nests is a favorite pastime.
The first eggs are laid in early November; if the incubating egg is left unattended for more than an hour or two, it will cool and become infertile. When nests are abandoned the eggs are easy prey for skuas, which are the Adelie penguin's main enemy on land. Males and females take turns incubating the eggs. Within hours of laying the eggs, the female returns to the sea, leaving the male to stand alone for up to ten days while his partner feeds. Most pairs produce two eggs separated by an interval of two to three days, and incubation takes about thirty days. While the two chicks hatch almost simultaneously, inevitably one chick is stronger and consequently better able to win food from its parents.
The chicks are fed from the crop of whichever parent is present at the time. The chicks are brooded closely by their parents for the first two to three weeks and their appetite is considerable. Growing rapidly, the chicks soon develop a thick woolly gray down and quickly become almost as large as their parents. During the third or fourth week they join other chicks in crèches or nursery groups. This leaves both parents free to go to sea to feed themselves in order to satisfy their chicks' increasing demands for food.
A parade of adults can regularly be seen moving between the colony and the sea. The birds congregate in large numbers at the water's edge waiting for the appropriate moment to take the plunge. The Adelie's main oceanic predators are the leopard seals which often lie in wait beneath the ledges to snare the first penguin into the water. By late March most Adelies have left the colonies to spend the winter in the comparative warmth of the offshore pack ice.
Adelie penguins provided generations of early explorers with entertainment,
palatable eggs, and tough but tasty meat. Through detailed studies
of the birds's breeding and eating behavior, scientists today
use the Adelie as an indicator species to monitor the abundance
of krill, so important to the web of Antarctic life. Return
Emperor penguins are the most biologically interesting of the southern species. They have been recorded diving to a depth of more than 1500 feet (450 m) for up to 18 minutes, although the usual depth and duration of their dives is much less. But it is their unique breeding behavior that differentiates the Emperor from other penguin species.
Rather than breeding during the warmer, lighter summer months, Emperors breed through the cold, dark winter. The female lays a single egg in May after a 63-day gestation period, and then passes the egg over to her mate and goes to sea to feed. When the male takes over the incubation, he fasts for 9 weeks, all the while balancing the egg on his feet, where it is insulated by a thick roll of skin and feathers. During this period the males huddle together for added warmth and protection against the bitter winds and sub-zero temperatures. By the time the female returns the male will have lost up to one third of his body weight; she takes over feeding the now-hatched chick for a six week period, while the male makes another long trek over the ice -- up to 60 miles (100 kms) to find food.
Once the young are about seven weeks old, they join other chicks
in a crèche, which is protected by a few adults. By January
the sea-ice begins to break out, but by this time the chicks have
begun to shed their soft down and are able to fend for themselves.
The Emperors are believed to have developed this winter breeding
pattern to allow the chick to grow to independence at a time when
food is most plentiful. The large size of the adults means they
can store enough fat to withstand the long winter weeks without
regular feeding. Return
Gentoo Penguins (Pygoscelis papua)Gentoos (jen-TOOs) are found over the widest range of any penguin, appearing on the coastal islands as well as the cooler sub-antarctic islands. The Gentoo penguin is the largest of the brush-tailed genus, averaging some 30 inches (75 cm) and weighing 12 pounds (5.5kg). They breed mainly on the Antarctic Peninsula and sub-antarctic islands. Two eggs are laid in September or October and hatching usually takes about 35 to 39 days from the laying of the last egg. The second egg is smaller than the first, and is laid three days later. After they are three-quarters grown, the young can look after themselves and leave the nests to form large crèches, usually in January. Gentoos are thought to fish closer to the surface than other species, although they can dive to at least 330 feet (100m). Return
Chinstrap Penguin (Pygoscelis antarctica)Chinstrap penguins are named for the distinctive narrow band of black feathers that extends from ear to ear. Chinstraps may be the most numerous of penguins, with a population estimated at 12 to 13 million. Yet they occur only on the Antarctic Peninsula and the sub-antarctic islands south of the Antarctic Convergence. For nesting, they often select lofty sites that are the first to become snow-free, to ensure the maximum amount of time to raise their chicks. Chinstraps are regarded as the boldest and most pugnacious of the pygoscelid species; they average 28 to 29 inches (71 to 76 cm) in height and weigh some 8.6 to 9.7 pounds (3.9 - 4.4 kg). Return
The Crested PenguinsOther species of penguins found in Antarctica occur mostly in the warmer sub-antarctic regions to the north, away from the limit of the pack-ice. These include the Rockhopper, the Macaroni (both of the crested genus), and the King penguin. The King breeds on South Georgia, and Macquarie and Heard islands, while the Macaroni occurs as far south as the South Shetlands. Rockhopper penguins do not breed south of Heard Island (53°S), located in the mid-South Atlantic between South America and Australia. Return
|Photography ©Jonathan Chester, Extreme Images||© 1995 Terraquest. All Rights Reserved.|