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Information about PenguinsPenguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica, where they are most well-known for living. Highly adapted for life in the water, Penguins have countershaded dark and white plumage, and their wings have become flippers. Most Penguins feed on krill, fish, squid, and other forms of sealife caught while swimming underwater. They spend about half of their life on land and half in the oceans.
Although all penguin species are native to the southern hemisphere, they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos Penguin, lives near the equator.
The largest living species is the Emperor Penguin (Aptenodytes forsteri (4 walls)): 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). Among extant Penguins, larger Penguins inhabit colder regions, while smaller Penguins are generally found in temperate or even tropical climates (see also Bergmann's Rule). Some prehistoric species attained enormous sizes, becoming as tall or as heavy as an adult human (see below for more). These were not restricted to Antarctic regions; on the contrary, subantarctic regions harboured high diversity, and at least one giant penguin occurred in a region not quite 2,000 km south of the equator 35 mya, in a climate decidedly warmer than today.
EvolutionThe evolutionary history of Penguins is well-researched and represents a showcase of evolutionary biogeography; though as penguin bones of any one species vary much in size and few good specimens are known, the alpha taxonomy of many prehistoric forms still leaves much to be desired. Some seminal articles about penguin prehistory have been published since 2005 (12 years ago), the evolution of the living genera can be considered resolved by now.
The basal Penguins lived around the time of the Cretaceous–Tertiary extinction event somewhere in the general area of (southern) New Zealand and Byrd Land, Antarctica. Due to plate tectonics, these areas were at that time less than 1,500 kilometers (932 mi) apart rather than the 4,000 kilometers (2,485 mi) of today. The most recent common ancestor of Penguins and their sister clade can be roughly dated to the Campanian–Maastrichtian boundary, around 70–68 mya. What can be said as certainly as possible in the absence of direct (i.e., fossil) evidence is that by the end of the Cretaceous, the penguin lineage must have been evolutionarily well distinct, though much less so morphologically; it is fairly likely that they were not yet entirely flightless at that time, as flightless birds have generally low resilience to the breakdown of trophic webs which follows the initial phase of mass extinctions because of their below-average dispersal capabilities.
BehaviourPenguins for the most part breed in large colonies, the exceptions being the Yellow-eyed and Fiordland species; these colonies may range in size from as few as a 100 pairs for Gentoo Penguins, to several hundred thousand in the case of King, Macaroni and Chinstrap Penguins. Living in colonies results in a high level of social interaction between birds, which has led to a large repertoire of visual as well as vocal displays in all penguin species. Agonistic displays are those which are intended to confront or drive off, or alternately appease and avoid conflict with, other individuals.
Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most Penguins lay two eggs in a clutch, although the two largest species, the Emperor and the King Penguins, lay only one. With the exception of the Emperor Penguin, in all Penguins share the incubation duties. These incubation shifts can last days and even weeks as one member of the pair feeds at sea.
Penguins generally only lay one brood; the exception is the Little Penguin which can raise two or three broods in a season.
Penguin eggs are smaller than any other bird species when compared proportionally to the weight of the parent birds; at 52 g (2 oz), the Little Penguin egg is 4.7% of its mothers' weight, and the 450 g (1 lb) Emperor Penguin egg is 2.3%. The relatively thick shell forms between 10 and 16 % of the weight of a penguin egg, presumably to minimise risk of breakage in an adverse nesting environment. The yolk, too, is large, and comprises 22–31 % of the egg. Some yolk often remains when a chick is born, and is thought to help sustain it if parents are delayed in returning with food.
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. In some species, such as Emperor Penguins, young Penguins assemble in large groups called crèches.
SubspeciesAptenodytes – Great Penguins
King Penguin, Aptenodytes patagonicus (6 walls)
Emperor Penguin, Aptenodytes forsteri (4 walls)
Pygoscelis – Brush-tailed Penguins
Adelie Penguin, Pygoscelis adeliae (2 walls)
Chinstrap Penguin, Pygoscelis antarctica
Gentoo Penguin, Pygoscelis papua
Eudyptula – Little Penguins
Little Blue Penguin, Eudyptula minor
Northern Little Penguin, Eudyptula albosignata (provisional)
Spheniscus – Banded Penguins
Magellanic Penguin, Spheniscus magellanicus
Humboldt Penguin, Spheniscus humboldti
Galapagos Penguin, Spheniscus mendiculus
African Penguin, Spheniscus demersus
Yellow-eyed Penguin, Megadyptes antipodes
Waitaha Penguin, Megadyptes waitaha (extinct)
Eudyptes – Crested Penguins
Fiordland Penguin, Eudyptes pachyrynchus
Snares Penguin, Eudyptes robustus
Erect-crested Penguin, Eudyptes sclateri
Southern Rockhopper Penguin, Eudyptes chrysocome
Northern Rockhopper Penguin, Eudyptes moseleyi
Royal Penguin, Eudyptes schlegeli (disputed)
Macaroni Penguin, Eudyptes chrysolophus
Chatham Islands Penguin, Eudyptes sp. (extinct)
Relationship with humansPenguins seem to have no special fear of humans, and have approached groups of explorers without hesitation. This is probably because Penguins have no land predators in Antarctica or the nearby offshore islands. Instead, Penguins are at risk at sea from predators such as the leopard seal. Typically, Penguins do not approach closer than about 3 meters (10 ft) at which point they become nervous. This is also the distance that Antarctic tourists are told to keep from Penguins (tourists are not supposed to approach closer than 3 meters, but are not expected to withdraw if the Penguins come closer).
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