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Emperor Penguin

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Emperor Penguin
Image:EmperorPenguin 2005 2592.JPG
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Sphenisciformes
Family: Spheniscidae
Genus: Aptenodytes
Species: A. forsteri
Binomial name
Aptenodytes forsteri
Gray, 1844

The Emperor Penguin (Aptenodytes forsteri) is the tallest and heaviest of all living penguin species. It is endemic to Antarctica, and is the only penguin species that breeds during the Antarctic winter. Emperor Penguins mainly eat fish but also take crustaceans (such as krill) and squid. Emperor Penguins typically live for 20 years in the wild, but some records indicate a maximum lifespan of around 40 years. The Emperor Penguin should not be confused with the closely related King Penguin or the Royal Penguin.

Contents

Taxonomy

The Emperor Penguin was described in 1844 by English zoologist George Robert Gray, its generic name derived from the Ancient Greek a/α 'without' pteno-/πτηνο- 'feather' or 'wing' and dytes/δυτης 'diver'.[2] Its specific epithet is in honour of the German naturalist Johann Reinhold Forster, who accompanied Captain James Cook on his second Pacific Voyage and officially named five other penguin species.

Together with the similarly coloured but smaller King Penguin (A. patagonicus), it is one of two extant species in the genus Aptenodytes. Ridgen's Penguin (A. ridgeni) is an extinct species known from fossil bones of the Late Pliocene, around 3 million years ago, in New Zealand.[3]

Description

The adult Emperor Penguin stands up to about 122 cm (48 in) tall and can weigh anywhere from 22 to 37 kg, depending on where it is in the reproductive cycle, because both male and female penguins lose substantial portions of their mass while raising hatchlings and incubating eggs.[4] The adult has deep black feathers dorsally, including the head, chin, throat, back, dorsal part of the flippers, and tail. These dark feathers fade to a brownish color as they become worn, usually between December and February.[4] The belly is white from the upper breast to venter and the underparts of the wings. The upper mandible is black, and the lower mandible can be pink, orange or lilac. Males and females are similar in size and coloration.[4] A juvenile emperor penguin is similar in size and coloration to an adult, but its auricular patches, chin and throat are white.[4] Emperor Penguin chicks are covered with silver-gray down with a black head and white eye and cheek patches.[4] They weigh around 315 g on hatching, and fledge at around 50% of adult weight.[5]

Moulting is a rapid process in penguins compared with other birds, taking around 34 days in this species in January and February. Emperor Penguin feathers emerge from the skin after developing to one third total length, and before old feathers are lost, to reduce heat loss. New feathers then push old ones out, before finishing their growth.[6]

The average yearly survival rate has been measured at 95.1%, with an average life expectancy of 19.9 years. The same researchers estimate 1% of Emperor Penguins born could feasibly reach and age of 50 years.[7]

Vocalization

As they have no fixed nest sites, they are unable to use the location of nest-sites to find partners or chicks and hence rely on being able to identify them by call alone.[8] The Emperor Penguin utilizes a complex set of calls that are critical to individual recognition between parents, offspring, and mates,[4] displaying the widest variation in individual calls of all penguins.[8] Its calls are known for using two frequency bands simultaneously.[9] Chicks use a frequency-modulated whistle to beg for food and to contact parents.[4]

Distribution and habitat

The Emperor Penguin has a circumpolar distribution, found almost exclusively in the Antarctic ranging from 66º to 77º south latitude. It almost always breeds on stable pack ice near the coast and up to 18 km (11 mi) offshore.[4] Breeding colonies usually occur in sheltered areas where ice cliffs and icebergs protect against the wind.[4] Around 80,000 pairs breed in the Ross Sea sector.[10] Major breeding colonies are located at Cape Washington with 20-25,000 pairs, Coulman Island, Victoria Land with 21708 pairs, Halley Bay, Coats Land with 14,300-31,400 pairs, and Atka Bay in Queen Maud Land with 16,000 pairs.[11] Vagrants have been recorded on Heard Island,[12] South Georgia, and New Zealand.[13][11]

Behavior

Emperor Penguins, Ross Sea, Antarctica
Emperor Penguins, Ross Sea, Antarctica

Emperor Penguins are social animals, both foraging and nesting in groups. In severe weather the penguins huddle together for protection. They may be active day or night. Mature adults travel throughout most of the year between the nesting area and foraging areas in the ocean. From January to March, Emperor Penguins disperse into the oceans, traveling and foraging in groups. It is estimated that there are around 400,000-450,000 Emperor Penguins, distributed into as many as 40 independent Antarctic colonies.[11]

The study of penguin foraging behaviour was revolutionized in 1971, when American Gerry Kooyman published research having attached automatic dive recording devices to Emperor Penguins. He found they had reached depths of 265 m (869 ft). He also noted a maximum dive period of 18 minutes in the same report.[14] Later research revealed a small female dived to a depth of 535 m (1,755 ft) near McMurdo Sound. It is possible that the species can dive even deeper as the water pressure at these depths impacted on the recording devices.[15] Male and female Emperor Penguins forage for food up to 500 km (311 mi) from colonies while collecting food to feed chicks, covering anywhere between 82 and 1454 km (51 and 904 miles) per individual trip. Those males returning to the sea after incubation head directly out to areas of permanent open water, known as polynyas, around 100 km (62 mi) from the colony..[16]

Its swimming speed is 6 to 9 km/h (4 to 6 mph), but they can achieve up to 19 km/h (12 mph) in short bursts. On land they alternate between walking with a wobbling gait and sliding over the ice on their bellies, propelled by their feet and their wing- like flippers.

Image:EmperorPenguinColonyClose.jpg
Emperor Penguin colony

As a defense against the cold, Emperor Penguins stand in compact huddles (also known as the turtle formation) ranging in size from ten to many hundreds of birds, with each bird leaning forward on a neighbor.[17] Those on the outside tend to shuffle slowly around the edge of the turtle, producing a slow churning action, and giving each bird a turn on the inside and the outside. Without this behaviour, male Emperor Penguins would be unable to survive the brutal Antarctic winter.

Diet

The Emperor Penguin eats primarily fish, crustaceans and cephalopods.[18] The exact composition of the prey varies from population to population, but fish is usually the most important food source, and Antarctic silverfish, Pleuragramma antarcticum, is often the most important species eaten. It searches for prey in the open water of the Southern Ocean or in ice-free areas of open water and tidal cracks in pack ice.[4] One of its feeding strategies is to dive to around 50 m (164 ft), where it can easily spot the sub-ice fish, Pagothenia borchgrevinki, swimming against the under surface of the sea-ice, which it then catches. It then dives again and repeats the sequence about half a dozen times before surfacing to breathe. The Emperor Penguin may also blow bubbles into the cracks in the ice to drive out the hiding fish.

Predators

Image:Skua over penguins chicks.jpg
Skua flying over Emperor Penguin chicks, Ross Sea, Antarctica

The Emperor Penguin's predators include birds and aquatic mammals; the Southern Giant Petrel (Macronectes giganteus) is the main bird predator, responsible for up to 34% of chick deaths at some colonies. The South Polar Skua (Stercorarius maccormicki) mainly scavenges, as the chicks are too large to be attacked by the time it arrives.[19]

The primary aquatic mammal predators are the Leopard Seal (Hydrurga leptonyx), which takes fledglings soon after entering the water as well as some adult birds,[20] and the orca (Orcinus orca), which takes adult birds.[21]

Courtship and reproduction

Image:PENGUIN LIFECYCLE H.JPG
The life-cycle of the Emperor Penguin

The Emperor Penguin is able to breed at around three years of age, and usually commences breeding around 1-3 years later.[5] They travel about 90 km (56 mi) inland to reach the breeding site. The trigger for the reproductive cycle appears to be decreasing daylength; Emperor Penguins in captivity have been induced successfully into breeding by using lighting systems mimicking seasonal Antarctic daylength.[22]

The penguins start courtship in March or April, when the temperature can be as low as –40°C (-40°F). A lone male will give an ecstatic display, where it stands still and places its head on its chest before inhaling and giving a courtship call for 1-2 seconds, then moving around the colony and repeating. A male and female will stand face to face, one extending its head and neck up and the other mirroring it before both hold this posture for several minutes. Once in pairs, couples will waddle around the colony together with the female usually following the male. Before copulation, one bird will bow deeply to its mate, its bill pointed close to the ground, and its mate will do the same.[23]

Emperor Penguins are serially monogamous. They have only one mate each year, and stay faithful to that mate. However, fidelity between years is only about 15%.[23] The narrow window period available for mating appears to be an influence, as there is a priority to mate and breed which often precludes waiting for the previous year's partner.[24]

Image:Aptenodytes forsteri egg hg.jpg
The egg of the Emperor Penguin. It is 12x8cm and vaguely pear-shaped.

The female penguin lays one 460-470 gram (1 lb) egg in May or early June;[23] it is pyriform (pear-shaped) and pale greenish-white in colour and measures around 12 x 8 cm.[25]15.7% of the weight of an Emperor Penguin egg is shell; like those of other penguin species, the shell is relatively thick to minimise risk of breakage.[26] It represents just 2.3 % of its mothers body weight, one of the smallest eggs relative to maternal weight of any bird species.[27]

At this point the mother's nutritional reserves are exhausted and she immediately returns to the sea to feed for two months.[25] Very carefully, she transfers the egg to the male, who incubates the egg in his brood pouch for 64 days consecutively until hatching.[23] The Emperor Penguin is the only species where this behaviour is observed, as both parents take shifts incubating in all other species.[28] By this time the male will have fasted for around 115 days since arriving at the colony.[23] The transfer of the egg can be awkward and difficult, and many couples drop the egg in the process. When this happens, the chick inside is immediately lost as the egg cannot withstand the low temperatures on the icy ground. To survive the cold and winds of up to 200 km/h (120 mph), the males huddle together, taking turns in the middle of the huddle. They have also been observed with their backs to the wind to conserve body heat.

Hatching may take up to 2-3 days to complete, and chicks are born semi-altricial and nidicolous. In other words, they have only a thin covering of down and are entirely dependent on their parents for food and warmth.[29] The young chick is brooded in what is called the guard phase, spending its time balanced on its parents' feet and sheltered by its pouch.[29] If the chick hatches before the mother's return, the father feeds it a curd-like substance composed of 59% protein and 28% lipid, which is produced by a gland in his esophagus.[30]

Image:EmperorPenguinFeedingChick.jpg
Emperor Penguin feeding a chick

The female penguin returns any time from hatching to ten days afterwards, from mid-July to early August.[25] She finds her mate among the hundreds of fathers via his call and takes over caring for the chick, feeding it by regurgitating the food that she has stored in her stomach. The male then leaves to take his turn at sea, spending around 24 days there before returning.[25] His trip is slightly shorter than before, because the melting of ice in the summer gradually decreases the distance between the breeding site and the open sea. About 45-50 days after hatching, the chicks huddle in a crèche for warmth and protection, still fed by their parents.[25] A crèche may comprise up to several thousand birds densely packed together and is essential for surviving the low antarctic temperatures.[31]

Eventually, both the chick and parents return to the sea and spend the rest of the summer feeding there. At the end of the summer the whole inland trip is repeated for all those penguins of breeding age, while the younger ones stay at the sea edge.

Relationship with humans

Cultural references

The Emperor Penguin has been the subject of several documentaries. In 1993, the species was featured in the BBC series Life in the Freezer, presented by David Attenborough. In 2005, the French documentary La Marche de l'empereur (released as March of the Penguins in the U.S.) spotlighted the penguins' reproductive cycle. The BBC and Attenborough covered the Emperor again in the 2006 series Planet Earth. Apsley Cherry-Garrard, the Antarctic explorer, said: "Take it all in all, I do not believe anybody on Earth has a worse time than an Emperor Penguin."[32] The computer-animated movie Happy Feet (2006) features Emperor Penguins as its primary characters, with one in particular that loves to dance, depicting them as endangered by a shrinking food supply. The computer-animated movie Surf's Up (2007) features a surfing Emperor Penguin named Zeke "Big-Z" Topanga. The NHL's Pittsburgh Penguins franchise is named after the Emperor Penguin, and an Emperor Penguin leads the team onto the ice each year prior to the start of the first home game of the season. Additionally, the mascot of Youngstown State University (Pete Penguin) is also an Emperor Penguin.

Conservation

The Emperor Penguin is listed as least concern by the IUCN. Along with nine other species of penguin, it is currently being considered for placement under the US Endangered Species Act. The primary reasons for this are declining food availability due to the effects of climate change, and industrial fisheries on the crustacean and fish populations. Other reasons for their placement on this list include such things as disease, foreign and introduced predators (this is more so for the other species of penguin than it is the Emperor), habitat destruction, and disturbance at breeding colonies by humans. Of particular concern is the impact of disturbance caused by tourism.[33]

Further reading

  • Deguine, Jean-Claude. 1974. Emperor Penguin: Bird of the Antarctic. The Stephen Greene Press, Vermont.
  • Rivolier, Jean. 1956. Emperor Penguins. Elek Books, London.
  • (1997) "Emperor Penguin", Great Book of Birds. Philadelphia: Courage Books. 
  • National Geographic CritterCAM additional feature on DVD version of March of the Penguins
  • Willy Puchner, Penguins - Traveling the World

References

  1. ^ BirdLife International (2004). Aptenodytes forsteri. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern
  2. ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4. 
  3. ^ Williams, p. 13
  4. ^ a b c d e f g h i j
  5. ^ a b
  6. ^ Williams (The Penguins) p. 45
  7. ^ Mougin J-L, van Beveren M (1979). "Structure et dynamique de la population de manchots empereur Aptenodytes forsteri de la colonie de l'archipel de Pointe Géologie, Terre Adélie". Compte Rendus Academie Science dé Paris 289D: 157-60. 
  8. ^ a b Williams (The Penguins) p. 68
  9. ^ Robisson P. (1992). "Vocalizations in Aptenodytes Penguins: Application of the Two-voice Theory" Auk 109(3): 654-658 [1]
  10. ^ Harper PC, Knox GA, Wilson GJ, Young EC (1984). "The status and conservation of birds in the Ross Sea sector of Antarctica", in Croxall JP, Evans PGH, Schreiber RW: Status and Conservation of the World's Seabirds. Cambridge: ICBP, pp. 593-608. 
  11. ^ a b c Marchant, S; Higgins PJ (1990). Handbook of Australian, New Zealand and Antarctic Birds, Vol. 1A. Melbourne: Oxford University Press. 
  12. ^ Downes MC, Ealey EHM, Gwynn AM, Young PS (1959). "The Birds of Heard Island". Australian National Antarctic Research Report Series B1: 1-35. 
  13. ^ Croxall JP, Prince PA (1983). "Antarctic Penguins and Albatrosses". Oceanus 26: 18-27. 
  14. ^ Kooyman GL, Drabek CM, Elsner R, Campbell WB (1971). "Diving behaviour of the Emperor Penguin Aptenodytes forsteri". Auk 88: 775-95. 
  15. ^ Williams (The Penguins) p. 89
  16. ^ Ancel A, Kooyman GL, Ponganis PJ, Gendner JP, Lignon J, Mestre X (1992). "Foraging behaviour of Emperor Penguins as a resource detector in Winter and Summer". Nature 360: 336-39. 
  17. ^ Pinshow B., Fedak M.A. , Battles D.R, & Schmidt-Nielsen K. (1976) "Energy expenditure for thermoregulation and locomotion in emperor penguins" American Journal of Physiology 231(3): 903-912
  18. ^ Cherel Y. & Kooyman G. L. (1998) "Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica" Marine Biology 130(3): 335-344 doi:10.1007/s002270050253
  19. ^ Williams (The Penguins) p. 40
  20. ^ Kooyman GL, Croll DA, Stone S, Smith S (1990). "Emperor penguin colony at Cape Washington, Antarctica". Polar Record 26 (157): 103-08. 
  21. ^ Prévost, J (1961). Ecologie du manchot empereur. Paris: Hermann. 
  22. ^ "The endocrine control of reproduction and molt in male and female Emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliae) Penguins. I. Annual changes in plasma levels of gonadal streroids and luteinizing hormone.". Gen. Comp. Endocrinol 62: 43-53. 
  23. ^ a b c d e
  24. ^ Williams (The Penguins) p. 55
  25. ^ a b c d e
  26. ^ Williams (The Penguins) p. 24
  27. ^ Williams (The Penguins) p. 23
  28. ^ Williams (The Penguins) p. 27
  29. ^ a b
  30. ^ Prévost J, Vilter V (1963). "Histologie de la sécrétion oesophagienne du Manchot empereur". Proceedings of the XIII International Ornithological Conference: 1085-94. 
  31. ^ Williams (The Penguins) p. 30
  32. ^ Apsley Cherry-Garrard. From the Introduction to The Worst Journey in the World.
  33. ^ Burger J. & Gochfeld M. (2007) "Responses of Emperor Penguins ( Aptenodytes forsteri ) to encounters with ecotourists while commuting to and from their breeding colony". Polar Biology 30(10): 1303-1313 doi:10.1007/s00300-007-0291-1


Cited text

  • Williams, Tony D. (1995). The Penguins. Oxford, England: Oxford University Press. ISBN 0-19-854667-X. 

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