Penguins
Penguins consist of seventeen species of flightless seabird found in the Southern hemisphere. They are characterized by their erect posture, stiff wings, excellent swimming ability, awkward movement out of water, and coloring. Penguins are contained within the taxonomic order Sphenisciformes and its single family Spheniscidae.
 King Penguin. Source: Yan Ropert-Coudert/WoRMS/Encyclopedia of Life |
|
Scientific Classification Kingdom: Animalia (Animals) |
The characteristic coloring of penguins (black backs and white fronts) make them difficult to detect when swimming, blending against the sea from above and the sky from below. The waterproof feathers of penguins are interlocking with small muscles. This allows them to be held close to the body (reducing air and buoyancy) for better swimming and slightly apart from the body (allowing an insulating layer of air to form) for greater warmth in cold climates, although they also possess a layer of blubber under the skin, which acts as a powerful insulating layer when in water. Feathers remain waterproof by constant preening during which an oily substance (also containingwax), produced bythe uropygialgland at the base ofthe tail, is applied to the feathers. Penguins can dive to great depths, from 100 meters to up to 500 meters (King penguins.)
Penguins probably acquired their name because of their similar appearance to the now extinctGreat Auk, another flightless bird in the Northern hemisphere which wascalled pen gwyn, meaning "white head", in the Welsh language.
Contents
Penguin Species
There are 17 species of penguins in six genera as follows:
- Great penguins (Aptenodytes) 1. Emperor penguin (Aptenodytes forsteri) 2. King penguin (Aptenodytes patagonicus)
- Crested penguins (Eudyptes) 3. Rockhopper penguin (Eudyptes chrysocome) 4. Macaroni penguin (Eudyptes chrysolophus) 5. Fiordland crested penguin (Eudyptes pachyrynchus) 6. Snares crested penguin (Eudyptes robustus) 7. Royal penguin (Eudyptes schlegeli) 8 . Big-crested penguin (also Erect-crested penguin) (Eudyptes sclateri)
- Eudyptula 9. Little penguin (also Little Blue penguin and Blue penguin) (Eudyptula minor)
- Megadyptes 10. Yellow-eyed penguin (Megadyptes antipodes)
- Brush-tailed penguins (Pygoscelis) 11. Adelie penguin (Pygoscelis adeliae) 12. Chinstrap penguin (Pygoscelis antarcticus) 13. Gentoo penguin (Pygoscelis papua)
- Banded penguins (Spheniscus) 14. Black-footed penguin (also African penguin and Jackass penguin) (Spheniscus demersus) 15. Humboldt penguin (Spheniscus humboldti) 16. Magellanic penguin (Spheniscus magellanicus) 17. Galapagos penguin (Spheniscus mendiculus)
Physical Description
Penguins have a number of characteristic physical features, such as their erect posture, stiff wings, and counter-shaded body coloring (dark backs and white fronts).
Penguins are medium to large birds. The smallest (the Little Penguin) is typically 40 cm (16 inches) tall and a body mass of one kilogram (2.2 lbs); while the Emperor Penguin can reach 1.15 meters (43 inches) and attain a body mass of 22-37 kg (50-80 lbs.)
The adult plumage of penguins is blue-black or gray dorsally (back) and white ventrally (front). Some penguins, particularly Crested Penguins have distinctively colored feathers on their heads. Their counter-shading make penguins difficult to see by both predators and prey when swimming,allowing them to blend in against the dark sea from above and with the light sky from below.
Chicks are either entirely brown-gray, or white ventrally. Immature birdshave adult-like plumage, but are much duller, without the coloured ornamental crest feathers, or lacking the distinctive face patterns.
Male and female penguins are very similar in appearance and can be impossible to distinguish without behavioral cues (referred to as monomorphic).
Penguin feathers are small and continuous (i.e. no feather tracts), interlocking with small muscles, and are waterproof. This allows them to be held close to the body when swimming, thereby reducing the size of the air spaces close to the body and therefore reducing their buoyancy. This feature allows penguins to dive to greater depths than other birds, and also enables them to be more effective predators underwater. When out of water, penguin feathers can be held slightly away from the body, which creates an insulating layer of air for greater warmth in cold climates. Feathers remain waterproof by constant preening during which an oily secretion containing a waxy substance, produced by a gland from the base of the tail (the uropygial gland), is applied over the feathers. All penguins must come to land once a year in order to molt, where they grow new feathers to replace their older, existing ones.
The beaks or bills of penguins vary in size and sharpness with species and reflect the feeding strategies of each particular species: for example, King and Emperor penguins eat fish and have longer, thinner bills, while Rockhopper and Macaroni penguins eat mainly smaller prey like krill and have have shorter, thicker bills.
The ears of penguins consist of two small holes covered by feathers. Like human ears, these are located on either side of the head. These birds have acute hearing exemplified by their amazing ability to distinguish the call of their mate or chick in their vast colonies and so locate them by sound rather than sight. Sound plays an important role in courtship and other aspects of penguin life.
Penguins have denser and stronger bones than most other birds. This is a considerable advantage when it comes to swimming and diving, enabling them to dive deeper and not be held back by too much bouyancy when in the water. Penguins are at the end of an evolutionary extreme, in that they have adapted more to a swimming lifestyle, of which these heavier bones are one such adaptation, with the resultant loss of any flight capability, where light, porous bones would provide an advantage.
Another major adaptation to the swimming lifestyle can be seen in the wings of penguins, which are stiff and serve as flippers to propel them through the water. They can also be used as and as a means of regulating body temperature when out of the water. The stiffness is a result of the bones being flatter and broader than in other birds with the elbow and wrist joints being nearly completely fused.
Penguin feet are short and are situated towards the rear of the body. This gives penguins their characteristic erect stance. Their short webbed feet serve as rudders and paddles in water to aid swimming, but onland, their position and form result in the ungainly waddling so characteristic of penguins out of the water.
Penguins have short wedge-shaped tails which they often use to help maintain balance when waddling on land.
Image Sources: 1. Rebeca Zapata Guardiola/WoRMS/Encyclopedia of Life; 2.Yan Ropert-Coudert/WoRMS/Encyclopedia of Life; 3.Thomas Mattern; 4. Petr Baum/BioLib/Encyclopedia of Life; 5.Christian Mehlführer; 6. Armin Rose/WoRMS/Encyclopedia of Life; 7. Martin Rauschert/WoRMS/Encyclopedia of Life; 8.Silvie Hojná, Petr Bašus/BioLib/Encyclopedia of Life; 9. Jim Ross/BioLib/Encyclopedia of Life; 10.Mark Putney
Reproduction
Penguins usually breed in large colonies with from hundred to tens of thousands of pairs. The largest penguin colony consists of five million Macaroni penguins on the island of South Georgia.
In colder locations, such as the Antarctic, and sub-Arctic, penguins breed in either spring or summer; while in warmer climates like Northern Chile/Peru and the Galapagos Archipelago, breeding occurs on a more continuous basis.
Courtship between penguins is varied and complex, but often includes "ecstatic displays" with loud vocalizations, movement of the head, spreading of wings, and even beak slapping.
Penguins form monogamous pairs which, in some species, appear to last a lifetime. Pairs also return regularly to the same location and even to same nest site from year to year.
The types of nests created by penguins depend on the location and environment in which they are breeding. Shallow depressions in soil, rock or even guano are common, often lined with pebbles, twigs or vegetation. In icy locations like Antarctica, penguins forgo nests and rest the egg on top of their feet, below a pouch-like fold of abdominal skin: this enables the penguins to transfer body heat to the egg.
Females typically lay two eggs per clutch (Great, Little and Black-footed penguins being exceptions, laying one, one-two, and two-three eggs respectively). Often, the the individual eggs may be laid several days apart. For many penguins, the second egg is larger than the first and is given preferential treatment during incubation and is the only one to hatch. However, in the case of Brush-tailed (Pygoscelis) and Banded (Spheniscus) penguins, both eggs hatch.
The tasks of incubating, brooding and feeding the chicks are usually shared between both the male and female. The specific assignment of these tasks is generally species-specific.
Incubation ranges from 30-64 days, with parents taking shifts with the eggs. Usually, the male takes the first incubation shift after the female has laid the clutch.
One of the longest incubation and fasting shifts occurs in the Emperor penguin which was shown in the popular 2004 documentary, The March of the Penguins. In the fall, after walking far across the ice of Antarctica to the ancestral breeding grounds Emperor penguin court and mate. The females lay one egg and return to the sea to feed. The males, who remain behind, fast while incubating their eggs (balanced on their feet and warmed by their bodies through contact with their 'Brood pouch') during the harsh Antarctic winter for an average of 54 days. The males huddle together and move constantly to keep warm, taking turns at the edge and interior of the huddle. The female returns at hatching time and assumes care of the chick, while the male returns to sea to feed after about two months of fasting.
More typical is the Rockhopper penguin, which lays its two eggs in November at the beginning of the southern summer. The chick from the second, larger egg is usually the only one to survive. The parents take turns in incubating the eggs for around 33 days. Once the chicks have hatched, the male will remain to brood them for the first 25 days, during which time he is fed by the female who brings food back to the nest, or else he fasts for the entire period.
Chicks need food provided by their parents, and rely on them for protection (altricial). They can take from ten weeks to a year (King penguin) to grow sufficiently to become more-or-less independent (i.e. develop into a fledgling). In some species, chicks remain with, and are regularly fed by, the adults until they have fledged. In other species, the chicks may be fed until they are nearly adult sized, then fast for several months while huddling with other chicks for warmth in a nursery, here called a 'creche'.
Average age of first breeding differs between the species, ranging from two to five years old.
Behavior
Depending upon the terrain, penguins on land will waddle along shorelines and ice, or hop from rock to rock, some species being more adept at one form of locomotion on land than another. When on ice or snow, penguins can move swiftly by tobogganing (sliding along on their belly and propelled by their wings and feet). Underwater, penguins use their modified wings (or 'flippers') to propel themselves forward, and it is this underwater 'flying', combined with the solidity of their bones, that enables them to reach great depths. The Emperor penguin is an exceptional diver and can stay submerged for 18 minutes and dive as deep as 500 meters (1,640 ft). Swimming speeds average two to three knots (3.7km/hr), but may reach 15-20 knots (27.8-37km/hr) for short distances. Swimming often includes porpoising (repeatedly breaking the water's surface with enough momentum to lift the bird into the air for about one meter), which may be carried out for reasons of speed, escaping predators or even purely to aid breathing (and possibly a combination of these factors).
Penguins are highly social, often breeding in large colonies. Some species forage cooperatively and may dive synchronously while foraging in small or large groups. Species that breed in large colonies often have elaborate visual and vocal displays.
Vocalizations are characterized as loud, short brays, grunts or whistles, the type depending upon species, for instance, banded penguins (Spheniscus) are also known as 'jackass penguins' because of their braying, while the giant penguins of the genus Aptenodytes most often whistle. In colonial species in which chicks group together in a nursery (or crèche) recognition of mates and offspring seems based on individually distinguishable calls.
Distribution
|
|
| |
| |
| |
| |
|
|
| |
| |
| |
| |
|
|
| |
| |
|
|
|
|
|
|
|
Food Habits & Predation
Penguins dive well and use their flippers to swim underwater in pursuit of prey items. Prey species include anchovies, pilchards, cuttlefish, squid, and krill.
Predators of penguins depend on their location. At sea, leopard and some other seals, Killer whales, and sharks will attack penguins. Ashore, penguins are prey to a variety of species, such as leopards in South Africa, and Weka (Gallirallus australis) in New Zealand, whilst introduced species such as stoats, rats and feral cats will feed on nesting birds.
Conservation Status
Twelve penguin species are included in the IUCN Red List of Threatened Species, three of these (Eudyptes sclateri, Megadytpes antipodes, Spheniscus mendiculus) are listed as Endangered. Major threats to wild populations include: destruction of breeding habitat, human disturbance / hunting pressures, egg and guano collection, predation by introduced mammals, commercial fishing, oil spills and even hybridization with other penguin species.
|
Least Concern |
|
Least Concern |
|
|
|
Vulnerable |
|
Vulnerable |
|
Vulnerable |
|
Vulnerable |
|
Endangered |
|
Least Concern |
|
Endangered |
|
Least Concern |
|
Least Concern |
|
Near Threatened |
|
Vulnerable |
|
Vulnerable |
|
Near Threatened |
|
Endangered |
Economic Importance for Humans
Historically, penguins were hunted and boiled to extract oil from the heavy layer of fat beneath the skin. At the turn of the century, approximately 150,000 Royal penguins (Eudyptes schlegeli) were harvested each year for 20 years from Macquarie Island (located south of New Zealand). On islands off of the coasts of Peru and Chile, penguin eggs and guano (dry bird droppings) are still collected for local use.
Evolution
The evolutionary relationships of penguins are unclear at this time. At least fifty penguin species are represented in the fossil record of the Southern Hemisphere and date back 60 million years to the Early Paleocene epoch. A common ancestry for penguins and tubenoses (Procellariiformes) has been suggested by the presence of tubular nostrils in fossil penguins and in the extant Little Penguin (Eudyptula minor). However, they have also been considered related to loons (Gaviidae), grebes (Podicipedidae), or cormorants (Phalacrocoracidae). DNA hybridization places penguins within an enlarged Ciconiiformes and estimates a close relationship between penguins, loons, frigate-birds and tubenoses (procellariids).
Further Reading
- Penguins of the World, Wayne Lynch, Firefly Books, 2007 ISBN: 1554072743
- Penguins!, Brutus Östling, Collins, 2007 ISBN: 0061198587
- The Nature of Penguins, Jonathan Chester, Celestial Arts, 2001 ISBN: 1587611201
- Spheniscidae Encyclopedia of Life (accessed March 28, 2009)
- Species 2000 & ITIS Catalogue of Life: 2009 Annual Checklist. Bisby FA, Roskov YR, Orrell TM, Nicolson D, Paglinawan LE, Bailly N, Kirk PM, Bourgoin T, Baillargeon G., eds (2009), Species 2000: Reading, UK.
- Order Sphenisciformes Howard, L. 2003. The Animal Diversity Web (online).(accessed March 28, 2009)
- International Penguin Conservation Work Group (accessed March 28 2009)
- New Zealand Penguins (accessed March 28, 2009)
- BirdLife International (accessed March 28, 2009)
- WoRMS, World Registry of Marine Species (accessed March 28, 2009)
- IUCN Red List (accessed March 28, 2009)
- Global Register of Migratory Species (accessed March 28, 2009)
