Penguin

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For other uses, see Penguin (disambiguation).
iPenguins
Fossil range: Paleocene-Recent
Chinstrap Penguin, Pygoscelis antarctica
Chinstrap Penguin, Pygoscelis antarctica
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Sphenisciformes
Sharpe, 1891
Family: Spheniscidae
Bonaparte, 1831
Modern Genera

Penguins (order Sphenisciformes, family Spheniscidae) are an order of aquatic, flightless birds living exclusively in the Southern Hemisphere.

Contents

Species and habitats

The number of penguin species has been and still is a matter of debate. The numbers of penguin species listed in the literature varies between 16 and 19 species. Some sources consider the White-Flippered Penguin a separate Eudyptula species, although today it is generally considered a subspecies of the Little Penguin (e.g. Williams, 1995; Davis & Renner, 2003). Similarly, it is still unclear whether the Royal Penguin is merely a color morph of the Macaroni penguin. Also possibly eligible to be treated as a separate species is the Northern population of Rockhopper penguins (Davis & Renner, 2003). Although all penguin species are native to the southern hemisphere, they are not, contrary to popular belief, found only in cold climates, such as Antarctica. In fact, only a few species of penguin actually live so far south. Three species live in the tropics; one lives as far north as the Galápagos Islands (the Galápagos Penguin).

The largest living species is the Emperor Penguin (Aptenodytes forsteri): adults average about 1.1 m (3 ft 7 in) tall and weigh 35 kg (75 lb) or more. The smallest penguin species is the Little Blue Penguin (also known as the Fairy Penguin), which stands around 40 cm tall (16 in) and weighs 1 kg (2.2 lb). Generally larger penguins retain heat better, and thus inhabit colder regions, while smaller penguins are found in temperate or even tropical climates (see also Bergmann's Rule). Some prehistoric species attained enormous sizes, becoming as high as an adult human; see below for more.

Most penguins feed on krill, fish, squid, and other forms of sealife caught while swimming underwater. They spend half of their life on land and half in the oceans.

When mothers lose a chick, they sometimes attempt to steal another mother's chick, usually unsuccessfully as other females in the vicinity assist the defending mother in keeping her chick.

Penguins seem to have no fear of humans and have approached groups of explorers without hesitation. This is probably on account of there being no land predators in Antarctica or the nearby offshore islands that prey on or attack penguins. Instead, penguins are at risk at sea from such predators as the leopard seal.

Evolution

The evolutionary history of penguins is poorly understood, as penguin fossils are rare. The oldest known fossil penguin species are the Waimanu, which lived in the early Paleocene epoch of New Zealand, about 62 million years ago. While they were not as well adapted to aquatic life as modern penguins (which first emerged in the Eocene epoch 40 million years ago), Waimanu were flightless and loon-like, with short wings adapted for deep diving. These fossils prove that prehistoric penguins were already flightless and seagoing, so their origins probably reach as far back as 65 million years ago, before the extinction of the dinosaurs. Penguin ancestry beyond Waimanu is not well known, though some scientists (Mayr, 2005) think the penguin-like plotopterids (usually considered relatives of anhingas and cormorants) may actually be an early sister group of the penguins, and that penguins may have ultimately shared a common ancestor with the Pelecaniformes.

During the Late Eocene and the Early Oligocene (40-30 MYA), some lineages of gigantic penguins existed. Nordenskjoeld's Giant Penguin was the tallest, growing nearly 1.80 meters (6 feet) tall. The heaviest known species was with at least 80 kg the New Zealand Giant Penguin. Both were found on New Zealand, the former also in the Antarctic.

Palaeeudyptines
Traditionally, most extinct species of penguins, giant or small, have been placed in the paraphyletic sub-family called Palaeeudyptinae. More recently, it is becoming accepted that there were at least 2 major extinct lineages, one or two closely related ones from Patagonia and at least one other with pan-Antarctic and subantarctic distribution. For a complete list of these generarations, see below.

Systematics

(updated after Marples, 1962, and Acosta Hospitaleche, 2004)

ORDER SPHENISCIFORMES

    • Not assigned to a subfamily (all fossil)
      • Dege
      • Duntroonornis
      • Eretiscus
      • Insuza
      • Korora
      • Marplesornis
      • Marambiornis
      • Mesetaornis
      • Nucleornis
      • Pseudaptenodytes
      • Tonniornis
      • Wimanornis

Anatomy

Penguins are superbly adapted to an aquatic life. Their wings have become flippers, useless for flight in the air. In the water, however, penguins are astonishingly agile. Within the smooth plumage a layer of air is preserved, ensuring buoyancy. The air layer also helps insulate the birds in cold waters. On land, penguins use their tails and wings to maintain balance for their upright stance.

All penguins are countershaded - that is, they have a white underside and a dark (mostly black) upperside. This is for camouflage. A predator looking up from below (such as an orca or a leopard seal) has difficulty distinguishing between a white penguin belly and the reflective water surface. The dark plumage on their backs camouflages them from above.

Diving penguins reach 6 to 12 km/h (3.7 to 7.5 mph), though there are reports of velocities of 27 km/h (17 mph) (which are more realistic in the case of startled flight). The small penguins do not usually dive deep; they catch their prey near the surface in dives that normally last only one or two minutes. Larger penguins can dive deep in case of need. Dives of the large Emperor Penguin have been recorded which reach a depth of 565 m (1870 ft) and last up to 20 minutes.

Penguins either waddle on their feet or slide on their bellies across the snow, a movement called "tobogganing", which allows them to conserve energy and move relatively fast at the same time.

Penguins have an excellent sense of hearing. Their eyes are adapted for underwater vision, and are their primary means of locating prey and avoiding predators; in air, conversely, they are nearsighted. Their sense of smell has not been researched so far.

They are able to drink salt water safely because their supraorbital gland filters excess salt from the bloodstream. [1][2][3] The salt is excreted in a concentrated fluid from the nasal passages.

Mating habits

Some penguins mate for life, while others for just one season. They generally raise a small brood, and the parents cooperate in caring for the clutch and for the young. During the cold season on the other hand the mates separate for several months to protect the egg. The male stays with the egg and keeps it warm, and the female goes out to sea and finds food so that when it comes home, the baby will have food to eat. Once the female comes back, they switch.

Male bonding behaviour

In early February 2004 the New York Times reported a male pair of Chinstrap penguins in the Central Park Zoo in New York City were partnered, and when given an egg which needed incubation, successfully hatched it. Other penguins in New York have also been reported to be forming same-sex pairs.[4]

This was the basis for the children's picture book And Tango Makes Three. The couple about whom the book was based, Roy and Silo, would see further interesting developments in their relationship when in September 2005, Silo left Roy for a female penguin.

Zoos in Japan and Germany have also documented male penguin couples.[5] The couples have been shown to build nests together and use a stone to replace an egg in the nest. Researchers at Rikkyo University in Tokyo, found twenty such pairs at sixteen major aquariums and zoos in Japan. Bremerhaven Zoo in Germany attempted to break up the male couples by importing female penguins from Sweden and separating the male couples; they were unsuccessful. The zoo director stated the relationships were too strong between the older couples.

Name

Penguin is thought by some to derive from the Welsh words pen (head) and gwyn (white), applied to the Great Auk, which had a conspicuous white patch between the bill and the eye (although its head was black), or from an island off Newfoundland known as "White Head" due to a large white rock. This may be, however, a false etymology created by Dr. John Dee in his book on Prince Madoc of Wales, supposedly one of the discoverers of America. By this Dee hoped to cement Queen Elizabeth I's claim, as a Tudor, to the New World. Penguins live nowhere near Newfoundland, nor do they generally have white heads, but they do look remarkably like Great Auks. According to another theory, the original name was pen-wing, with reference to the rudimentary wings of both Great Auks and penguins. A third theory is that penguin comes from the Latin pinguis (fat). This has added credibility because in two other Germanic languages, Dutch 'pinguïn' and German, 'Pinguin' both have the 'i' vowel too. While it has been replaced by an 'e' in the English spelling, it can still be heard. By simply looking at the word's pronunciation and comparing that to the Dutch and German words, one could assume a common Latin root - after the first Germanic sound shift (500-200 BC) that makes a PIE 'p' into a 'f'. However, a Welsh 'i' is often mutated to an 'e' in the English language so the Welsh origin is still arguable.

Penguins in popular culture

Tux the Linux mascot
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Tux the Linux mascot
Main article: Penguins in popular culture

Penguins are popular around the world, primarily for their unusually upright, waddling pace and (compared to other birds) lack of fear of humans. Their striking black and white plumage is often likened to a tuxedo suit and generates humorous remarks about the bird being "well dressed". Perhaps in reaction to this cutesy stereotype, fictional penguins are occasionally presented as grouchy or even sinister. Penguins have also been the subject of many books and documentary films.

External links

References

  1. ^ Animal Fact Sheets. Retrieved on 2006-07-21.
  2. ^ Humboldt Penguin :: Saint Louis Zoo. Retrieved on 2006-07-21.
  3. ^ African Penguins and Penguins of the World. Retrieved on 2006-07-21.
  4. ^ Columbia News Service: June 10, 2002: They're in love. They're gay. They're penguins... And they're not alone.. Retrieved on 2006-07-21.
  5. ^ 365gay.com: Gay Penguins Resist 'Aversion Therapy'. Retrieved on 2006-07-21.
  • Acosta Hospitaleche, Carolina (2004): Los pingüinos (Aves, Sphenisciformes) fósiles de Patagonia. Sistemática, biogeografía y evolución. Doctoral thesis, Department of Natural Sciences and Museum, Universidad Nacional de La Plata. La Plata, Argentina. [in Spanish] PDF fulltext
  • Davis; Lloyd S.; Renner; M. (1995). Penguins . London: T & A D Poyser. ISBN 0-7136-6550-5.
  • Marples, B. J. (1962): Observations on the history of penguins. In: Leeper, G. W. (ed.), The evolution of living organisms. Melbourne, Melbourne University Press: 408-416.
  • Mayr, G. (2005): Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae). Journal of Zoological Systematics and Evolutionary Research 43(1): 61-71. DOI:doi:10.1111/j.1439-0469.2004.00291.x PDF fulltext
  • Williams; Tony D. (1995). The Penguins - Spheniscidae . Oxford: Oxford University Press. ISBN 0-19-854667-X.

Gallery

Adelie penguin in Antarctica

African Penguin

Chinstrap Penguin hunting for krill

Humboldt Penguin at the Milwaukee County Zoological Gardens

Magellanic Penguin

Gentoo Penguin

Little Penguin - also called "Fairy Penguin"

Emperor Penguins

Gentoo Penguin at polish Arctowski base

Galapagos Penguin, Galapagos Islands

Galapagos Penguin, Galapagos Islands

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