Penguins
Penguins
Penguins are primitive, flightless birds that are highly specialized for marine life. Most penguins look rather similar, being generally black or dark-gray on
top with a white belly. Some species, however, have a crest on their head and/or patches of color on their head and throat. The legs are set wide apart and the wings are used as flippers. Most species of penguin live and breed on Antarctica, on islands near that continent, or on the southern coasts of South America, Australia, South Africa, or New Zealand. Four northern species inhabit the western coast of South America, as far north as the equatorial Galápagos Islands.
Penguins have unusual and distinct characteristics, and their relationship to other orders of birds is not fully understood. In fact, scientists dispute whether penguins should have their own superorder or even subclass. However, it is generally agreed that penguins belong to the Order Sphenisciformes and the family Spheniscidae. There are six genera of penguins and 16-18 species, depending on the taxonomic treatment.
Adaptations for marine life
Penguins have numerous adaptations to life in cold, marine conditions. The legs, effectively used as oars, are set wide apart and connect rather far back to the long and rounded body. Short, glossy feathers cover its body to form a dense, furlike covering, which is waterproof and helps keep the bird warm. Although all of the bones needed for flight are present in its wings, they are tightly bound to each other by ligaments and are shortened and flattened. Given these adaptations, the wings have become unfoldable flippers used in swimming. The muscles in the chest, which are used to move the wings, are proportionately quite large, extending from the neck to the lower portion of the abdomen. The triangular tail is used for steering while swimming.
Locomotion
Having legs located far back on their body makes it necessary for penguins to walk upright when on land. While some of the smaller species are fairly coordinated, the larger ones (such as the emperor penguin) are clumsy on land. Penguins do not always have to walk, however. On steep icy slopes, they may travel by sliding on their belly, using their feet to steer and the flippers to steady themselves.
Underwater, penguins can move swiftly; their normal speed is 3-6 mph (4.8-9.6 km/h), although they can move faster for short bursts. They have three basic modes of transporting themselves in the sea. The first form is underwater flight, used for rapid movement when feeding or avoiding a predator, such as a leopard seal. The second form is known as porpoising, and is used for traveling longer distances. When porpoising, penguins alternate between swimming deep in the water and leaping out of the surface. It is thought that this increases the overall speed by reducing water resistance when swimming; also, this type of swimming allows the bird to catch a quick breath of air without stopping. The final form of swimming is the duck-style, with head and tail held erect, which penguins assume just before going ashore, in order to orient themselves.
Penguins occasionally dive deeply in their quest for food, which consists primarily of fish and crustaceans. For example, Emperor penguins reportedly can dive 850 ft (260 m) below the surface and remain there for about 18 minutes.
Social behavior
Penguins are social animals; they travel, feed, breed, nest, and winter in large groups. On several Antarctic and sub-Antarctic islands, penguin colonies may have millions of birds. For example, up to two million royal penguins (Eudyptes schlegeli) congregate on Macquarie Island, 750 mi (1,200 km) southwest of New Zealand. There are about 10 million birds living on one of the South Sandwich Islands, located north of Antarctica.
There are several possible reasons for penguins’ highly social behavior. First, mature penguins tend to return to the area where they were born to breed. Second, in large groups they are safer from predators, such as skuas, sharks, killer whales, and especially leopard seals. Third, they learn about the location of food from each other. Fourth, group living provides better care for their young and protection against the cold.
Within the social structure, there are two levels: the family and the breeding group. Within the family, which consists of the parents and usually two chicks, the young are cared for and defended against other penguins. Within the breeding group, group defenses are used against skuas and vocal communication causes the birds to breed at about the same time.
Nesting
Penguins spend the majority of their time in the water, but their nesting colonies are often located miles away from the water. Penguins tend to mate with their partner from the prior year’s breeding season. The males stake out the territory, which could only be a few square yards. Nests are made in a wide variety of locations, depending on the species, and can be in a rock crevice or burrow, in the open with stick and grass, or on a bare patch of ground.
Usually all but the two largest species (the Emperor and King penguins) lay two eggs. The two large species lay only one egg. The emperor penguin (Aptenodytes forsteri) endures the worst breeding conditions of any bird in the world. After the female lays her egg during the dark Antarctic winter, she returns to the water to feed and regain her strength. While she is gone, the male incubates the egg on top of his feet. During this 64-day period, when the temperature can dip below 40°F (4°C), the male huddles with other males to stay warm and eats nothing but snow. When the chick is born, he feeds it with a milky substance he regurgitates. Both emperor and king penguins (Aptenodytes patavonicus) have their young in the winter, so that they will become independent in the summer when food is abundant. Newborns of all species are born covered with a thick layer of brown or gray down. This down molts into feathers that look like those of the adult when the bird is a juvenile.
Maintaining body temperature
When a penguin dives into the Antarctic Ocean, it plunges into water that is 40 degrees below its own body temperature. (A person without a wet suit can live about ten minutes in water that cold.) As a result, penguins have adapted certain mechanisms to keep themselves warm. First, each penguin has a 0.7-1.1 in (2-3 cm) thick layer of fat and thick, waterproof plumage to insulate itself. In addition, when in the water, the penguin is much more active than on land. Thus, its metabolism increases, producing more metabolic heat.
The coldest-weather species (the emperor penguin) has made additional adaptations for surviving the most extreme cold. The emperor penguin has the largest body of any penguin, measuring about 3 ft (1 m) tall and weighing 88 lb (40 kg). Thus, compared to birds with a smaller body, it has relatively less surface area exposed to the cold compared with its weight. It also has the most fat of any penguin species and can live for two to four months during the winter without eating. The emperor penguin also has more extensive feather cover than other species, including feathers on its bill and feet, except the toes. Its flippers
KEY TERMS
Skuas— Sea birds that prey upon penguins. Family Stercoriidae.
are shorter and feet are smaller than its relatives, reducing their exposure to the cold.
This heat insulation is very effective, sometimes too effective. The problem with the insulation is that penguins are always in danger of overheating. This is especially true when they are fighting or running during the warmest months of the polar year—December, January, and February.
Because penguin populations naturally undergo dramatic fluctuations, the impact of human activities on penguins is difficult to determine with certainty. Penguins were extensively hunted in the past by sailors, who used them for food and also extracted their oil. Penguins are now legally protected in most countries, but some are still hunted for food or use as bait. The most significant problems currently facing penguin populations include oil pollution, entanglement in fishing nets, and reduced fishing stocks due to commercial fishing. Ten species of penguins are thought to be threatened, with the Gala´pagos penguin (Spheniscus mendiculus) and the erect-crested penguin (Eudyptes sclateri) considered at highest risk.
Resources
BOOKS
Davis, L.S., and J.T. Darby, eds. Penguin Biology. New York: Academic Press, Inc., 1990.
del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World. Vol. 1, Ostriches to Ducks. Barcelona: Lynx Edicions, 1992.
Marion, R. Penguins: A Worldwide Guide. New York: Sterling Publishing Co., 1999.
Miller-Schwartze, Dietland. The Behavior of Penguins: Adapted to Ice and Tropics. Albany: State University of New York Press, 1984.
Reilly, P. Penguins of the World. New York: Oxford University Press, 1994.
Williams, T.D. The Penguins: Spheniscidae. New York: Oxford University Press, 1995.
PERIODICALS
Perkins, S. “Flightless Feathered Friends: New Tales of Penguin Evolution, Past and Present.” Science News 166 (November 27, 2004): 346´348.
Sun, L. “Relics: Penguin Population Programs.” Science Progress 84 (2001): 31´44.
Kathryn Snavely
Penguins
Penguins
Penguins are primitive, flightless birds that are highly specialized for marine life. Most species look
rather similar, being generally dark-blue or dark-gray on top with a white belly. Some species, however, have a crest on their head and/or patches of color on their head and throat. The legs are set wide apart and the wings are used as flippers. Most species of penguin live and breed on Antarctica , on islands near that continent , or on the southern coasts of South America , Australia , South Africa , or New Zealand. Four northern species inhabit the western coast of South America, as far north as the equatorial Galapagos Islands.
Penguins have unusual and distinct characteristics, and their relationship to other orders of birds is not fully understood. In fact, scientists dispute whether penguins should have their own superorder or even subclass. However, it is generally agreed that penguins belong to the Order Sphenisciformes and the family Spheniscidae. There are six genera of penguins and 16-18 species, depending on the taxonomic treatment.
Adaptations for marine life
Penguins have numerous adaptations to life in cold, marine conditions. The legs, effectively used as oars, are set wide apart and connect rather far back to the long and rounded body. Short, glossy feathers cover its body to form a dense, fur-like matting, which is waterproof and helps keep the bird warm. Although all of the bones needed for flight are present in its wings, they are tightly bound to each other by ligaments and are shortened and flattened. Given these adaptations, the wings have become unfoldable flippers used in swimming. The muscles in the chest, which are used to move its wings, are proportionately quite large, extending from the neck to the lower portion of the abdomen. The triangular tail is used for steering while swimming.
Locomotion
Having legs located far back on their body makes it necessary for penguins to walk upright when on land. While some of the smaller species are fairly coordinated, the larger ones (such as the Emperor penguin) are clumsy on land. Penguins do not always have to walk, however. On steep icy slopes, they may travel by sliding on their belly, using their feet to steer and the flippers to steady themselves.
Underwater, penguins can move swiftly; their normal speed is 3-6 mph (4.8-9.6 km/h), although they can move faster for short bursts. They have three basic modes of transporting themselves in the sea. The first form is underwater flight, used for rapid movement when feeding or avoiding a predator , such as a leopard seal. The second form is known as porpoising, and is used for traveling longer distances. When porpoising, penguins alternate between swimming deep in the water and leaping out of the surface. It is thought that this increases the overall speed by reducing water resistance when swimming; also, this type of swimming allows the bird to catch a quick breath of air without stopping. The final form of swimming is the duck-style, with head and tail held erect, which penguins assume just before going ashore, in order to orient itself.
Penguins occasionally dive deeply in their quest for food, which consists primarily of fish and crustaceans. For example, Emperor penguins reportedly can dive 850 ft (260 m) below the surface and remain there for about 18 minutes.
Social behavior
Penguins are social animals; they travel, feed, breed, nest, and winter in large groups. On several Antarctic and sub-Antarctic islands, colonies number in the millions. For example, up to two million royal penguins congregate on Macquarie Island, 750 mi (1,200 km) southwest of New Zealand. There are about 10 million birds living on one of the South Sandwich Islands, located north of Antarctica.
There are several potential reasons for penguins' highly social behavior . First, mature penguins tend to return to breed to the area where they were born. Second, in large groups they are safer from predators, such as skuas , sharks , killer whales, and especially leopard seals . Third, they learn about the location of food from each other. Fourth, group living provides better care for their young and protection against the cold.
Within the social structure, there are two levels: the family and the breeding group. Within the family, which consists of the parents and usually two chicks, the young are cared for and defended against other penguins. Within the breeding group, group defenses are used against skuas and vocal communication causes the birds to breed at about the same time.
Nesting
Penguins spend the majority of their time in the water, but their nesting colonies are often located miles away from the water. Penguins tend to mate with their partner from the prior year's breeding season. The males stake out the territory, which could only be a few square yards. Nests are made in a wide variety of locations, depending on the species, and can be in a rock crevice or burrow, in the open with stick and grass, or on a bare patch of ground.
Usually all but the two largest species (the Emperor and King penguins) lay two eggs. The two large species lay only one egg. The Emperor penguin endures the worst breeding conditions of any bird in the world. After the female lays her egg during the dark Antarctic winter, she returns to the water to feed and regain her strength. While she is gone, the male incubates the egg on top of his feet. During this 64 day period, when the temperature can dip below 40°F (4°C), the male huddles with other males to stay warm and eats nothing but snow. When the chick is born, he feeds it with a milky substance he regurgitates. Both Emperor and King penguins have their young in the winter, so that they will become independent in the summer when food is abundant. Newborns of all species are born covered with a thick layer of brown or gray down. This down molts into feathers that look like those of the adult when the bird is a juvenile.
Maintaining body temperature
When a penguin dives into the Antarctic Ocean, it is greeted by a water temperature 40 degrees below its own body temperature. (A person without a wet suit can live about 10 minutes in water that cold.) Thus, penguins have adapted certain mechanisms to keep themselves warm. First, each penguin has a 0.7-1.1 in (2-3 cm) thick layer of fat and thick, waterproof plumage to insulate itself. Further, when in the water, the penguin is much more active than when on land. Thus, its metabolism increases, producing more metabolic heat .
The coldest-weather species (the Emperor penguin) has made additional adaptations for surviving the most extreme cold. The Emperor has the largest body of any penguin, measuring about 3 ft (1 m) tall and weighing 88 lb (40 kg). Thus, compared to birds with a smaller body, it has relatively less surface area exposed to the cold compared with its weight. It also has the most fat of any penguin species and can live for two to four months during the winter without eating. The Emperor also has more extensive feather cover than other species, including feathers on its bill and feet, except the toes. Its flippers are shorter and feet are smaller than its relatives, reducing their exposure to the cold.
This heat insulation is very effective, sometimes too effective. The problem with the insulation is that penguins are always in danger of overheating. This is especially true when they are fighting or running during the warmest months of the polar year—December, January, and February.
Resources
books
Davis, Lloyd S., and John T. Darby. Penguin Biology. New York: Academic Press, Inc., 1990.
Jackson, Jerome A., ed. Grzimek's Animal Life Encyclopedia, Birds. Detroit, MI: Gale Group, 2002.
MacMillan Illustrated Animal Encyclopedia. New York: MacMillan Publishing Company, 1992.
Miller-Schwartze, Dietland. The Behavior of Penguins: Adapted to Ice and Tropics. Albany: State University of New York Press, 1984.
periodicals
Sun, L. "Relics: Penguin Population Programs." Science Progress 84, no.1 (2001):31-44.
Kathryn Snavely
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Skuas
—Sea birds that prey upon penguins. Family Stercoriidae.
Spheniscidae
penguin
Penguin Books the name of the paperback publishing imprint founded by Allen Lane in 1935; the first ten titles, published in 1936 and priced at sixpence each, included titles by Agatha Christie, Ernest Hemingway, and André Maurois.
penguin
pen·guin / ˈpenggwin; ˈpengwin/ • n. a large flightless seabird (family Spheniscidae) of the southern hemisphere, with black upper parts and white underparts and wings developed into flippers for swimming under water.