Penguins
Penguins (order Sphenisciformes, family Spheniscidae) are an order of aquatic, flightless birds living in the southern hemisphere.
Traditionally, most extinct species of penguins have been placed in the (possibly paraphyletic sub-family called Palaeeudyptinae.
There are 17 to 19 known species worldwide, depending on whether the two Eudyptula species are counted as distinct. 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) and will occasionally cross the equator while feeding.
The largest species is the Emperor Penguin (Aptenodytes forsteri): adults average about 1.1 meters (3 ft 7 in) tall and weigh 35 kilograms (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 kilogram (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. The rarest type of penguin is the yellow-eyed penguin (Megadyptes antipodes) and is probably the most ancient of all living penguins: adults average about 65 cm tall and weigh 5-6 kilograms.
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.
One of the most baffling forms of behavior of the penguin comes when a mother loses her chick, either due to its being unable to endure its first storm, or due to other reasons such as predators. When a mother loses its chick, they have been known to actually attempt to steal another mother's living chick- presumably in order to deal with the grief of the loss.
This behavior has amazed scientists, as it is an emotional outburst opposed to an instinctual behavior; something many wild animals do not exhibit when losing their young. Many have used this as prime evidence for decades that many animals have near human-like emotions and feelings, often for the sake of animal rights. Naturally, the other females in the penguin groups dislike this behavior and will help the defending mother keep her chick.
This behavior, however, might be better explained as a means for the female, or the male, to retain the full cooperation of the other parent in rearing the young, given that the bonding is monogamous; most likely there are differences between males and females in regards to the likelihood of chick-robbing and between species in relation to whether the monogamy is seasonal or permanent. Penguins seem to have no fear of humans, and have approached groups of explorers without hesitation.
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.
Anatomy
yPenguins 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. The plumage of penguins in tropical and temperate zones is much thinner than that of more southern species.
On land, penguins use their tails and wings to maintain balance for their upright stance.All penguins 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, though there are reports of velocities of 27 km/h (which are probably 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. The salt is excreted in a concentrated fluid from the nasal passages.
Penguins have no external genitalia. Consequently, chromosome testing must be done in order to determine a penguin's sex.
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.
Historic penguin sketches found - chalk drawings BBC - December 21, 2007
Penguins Safely Lower Oxygen to "Blackout" Levels National Geographic - December 8, 2007
Giant Penguins Once Roamed Peru Desert, Fossils Show National Geographic - June 25, 2007
Giant Prehistoric Penguins Found National Geographic - June 25, 2007
A Magellanic penguin whose natural habitat is the cool climes of southern Chile has strayed thousands of miles from his home, arriving in Peru BBC - May 11, 2007
Penguins survived when dinosaurs died ABC - April 7, 2006
The study incorporates genetic evidence of the evolutionary relationships between penguins' distant cousins like shearwaters, albatrosses, ducks and moas The researchers used DNA from these birds to provide a broad framework of family relationships which, together with the fossil evidence, is used to predict when those birds must have arisen.
"We're really confident we have ancient birds and really confident about the date," says Fordyce. "It's enabled us to establish an earlier timeframe for when groups of modern birds branched out."
Most of the New Zealand fossils, officially recognised as the Waimanu penguin genus, were discovered by amateur palaeontologist Al Mannering in the Waipara region just north of Christchurch. Some 60 million years ago New Zealand had already separate from Australia and Antarctica and was a low-lying land mass much closer to the South Pole. Waimanu manneringi would have developed in a polar habitat similar to today's yellow-eyed penguin, which it closely resemble Its long bill and condensed wing bones indicate that it would be quite at home eating and swimming in today's Antarctica, the researchers say.
Live Science - April 4, 2006
Penguins and other Antarctic seabirds are nesting and laying their eggs later than they did 50 years ago, a response, scientists say, to global climate change. Penguins and other Antarctic seabirds are nesting and laying their eggs later than they did 50 years ago, a response, scientists say, to global climate change.
While the effects of climate change on animal behavior have been well documented in the Northern Hemisphere, the effects are less well known south of the equator. In North America and Europe, cold-weather animals are generally shifting northward as the Arctic warms and the ice cap shrinks. A new study by two scientists at the Centre National de la Recherche Scientifique in France compiled data for Antarctic seabird nesting from 1950 to 2004. It reveals that nine species of birds are, on average, arriving nine days later to nest. The birds are also laying their eggs two days later. This runs opposite to shifts in avian habits in the Northern Hemisphere, where earlier springs and increased food availability has led to birds migrating and laying eggs earlier in the season.
In Antarctica, the delay appears to be tied to sea ice. Unlike western Antarctica, no major warming or cooling has occurred in eastern Antarctica since the 1950's. However, in eastern Antarctica, sea-ice range has reduced 12 to 20 percent since the 1950's, owing to global warming, scientists say. Yet localized cooling has caused the sea-ice season to increase by more than 40 days since the 1970's. These changes have been associated with a decline in abundances of krill and other marine organisms that are food resources for most Antarctic seabirds. This may partly explain the delay in seabirds' arrival and laying dates, the researchers say, since seabirds need more time to build up the reserves necessary for breeding.
The shift represents a seven-day compression of the prelaying period when birds set up territories, court, and females make their eggs, suggesting that the birds' reproductive processes have some plasticity. However, the scientists caution, if the seabirds continue to become less synchronized with their food source, and the sea ice continues to block their nesting sites, these species could suffer if they fail to respond appropriately, either through microevolution or behavior changes, to climate change. The species affected: emperor penguin, Adelie penguin, southern giant petrel, southern fulmar, Antarctic petrel, Cape petrel, snow petrel, Wilson's storm petrel and the south polar skua.
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