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Trang này viết về loài chim. Đối với ban nhạc, xem Emperor Penguin (âm nhạc).

Emperor penguin
Adults with a chick on Snow Hill Island, Antarctic Peninsula
Phân loại khoa học edit
Giới: Animalia
Ngành: Chordata
Lớp: Aves
Bộ: Sphenisciformes
Họ: Spheniscidae
Chi: Aptenodytes
Loài:
A. forsteri
Danh pháp hai phần
Aptenodytes forsteri
Gray, 1844
Emperor penguin range
(breeding colonies in green)

Cánh cụt hoàng đế (tên khoa học: Aptenodytes forsteri) là loài đặc hữu và là loài chim cao nhất và nặng nhất trong số tất cả những loài chim cánh cụt sống ở Châu Nam Cực. Con trống và con mái có bộ lông và kích thước tương tự nhau, chiều cao có thể đạt tới 122 cm (48 in) và cân nặng từ 22 đến 45 kg (49 đến 99 lb). Đầu và lưng chúng màu đen, bụng và chân màu trắng, ngực màu vàng nhạt và tai màu vàng tươi. Giống như tất cả các loài chim cánh cụt khác, cánh cụt hoàng đế không biết bay, cơ thể thuôn dài, đôi cánh nhỏ và dẹt cùng chân chèo thích nghi với môi trường nước. Thức ăn thường ngày của chim cánh cụt hoàng đế là cá, nhưng đôi khi chúng cũng ăn động vật giáp xác, các loài nhuyễn thể, động vật thân mềm và mực. Trong khi săn, loài này có thể lặn xuống dưới nước trên 20 phút và lặn sâu tới 535 m (1.755 ft). Chúng có một số cơ chế giúp thích nghi với điều kiện này, bao gồm một hemoglobin có cấu trúc bất thường cho phép nó hoạt động ở nơi có nồng độ ôxy thấp, xương rắn để giảm chấn thương áp suất cùng khả năng giảm sự trao đổi chất ở cơ thể và tắt các chức năng cơ quan không cần thiết.

Là loài cánh cụt duy nhất sinh sản vào mùa đông ở châu Nam Cực,[2] cánh cụt hoàng đế phải di chuyển quãng đường 50–120 km (31–75 mi) trên băng để tới khu vực sinh sản, nơi có hàng ngàn cá thể khác. Những con mái sẽ đẻ ra một quả trứng duy nhất, con trống sẽ lo việc ấp trứng trong vòng hai tháng, còn con mái ra biển kiếm mồi; Sau đó, con trống và con mái thay nhau tìm kiếm thức ăn ngoài biển và chăm sóc cho cánh cụt con ở nơi sinh sản. Tuổi thọ của chim cánh cụt hoàng đế là 20 năm, mặc dù có một số con có thể sống tới 50 tuổi.

Phân loại[sửa | sửa mã nguồn]

Chim cánh cụt hoàng đế đã được nhà động vật học người Anh George Robert Gray mô tả năm 1844. Ông đã đặt tên cho loài chim này dựa vào tiếng Hy Lạp cổ đại ἀ-πτηνο-δύτης [a-ptēno-dytēs] có nghĩa là "thợ lặn không cánh". Tên cụ thể của nó để vinh danh nhà tự nhiên học người Đức Johann Reinhold Forster, người đã đi cùng thuyền trưởng James Cook trong chuyến du hành trên Thái Bình Dương lần thứ hai và chính thức đặt tên cho năm loài chim cánh cụt.[3] Forster có thể là người đầu tiên nhìn thấy các con chim cánh cụt vào năm 1773–74, khi ông ghi nhận đã nhìn thấy loài mà ông tin là giống với cánh cụt vua (A. patagonicus) nhưng dựa vào vị trí, có thể khá chắc rằng đó là loài A. forsteri.[4]

Tương tự với chim cánh cụt vua, chim cánh cụt hoàng đế là một trong hai loài còn tồn tại của chi Aptenodytes. Bằng chứng hóa thạch của loài cánh cụt thứ ba trong chi Aptenodytes - chim cánh cụt Ridgen (A. ridgeni) đã được tìm thấy tại New Zealand, ước tính chúng sống vào cuối thế Pliocen, tức hơn 3 triệu năm trước.[5] Nghiên cứu về hành vi và di truyền của chim cánh cụt, các nhà khoa học đã đưa ra giả thuyết rằng chi Aptenodytes là chi cơ bản; nói cách khác, nó tách ra từ một nhánh bao gồm tất cả các loài cánh cụt khác.[6] Các bằng chứng về ty thể và nhân DNA cho thấy việc tách nhánh này diễn ra cách đây 40  triệu năm.[7]

Mô tả[sửa | sửa mã nguồn]

Con trưởng thành và con non

Chim cánh cụt hoàng đế trưởng thành khi đứng có chiều cao 110–130 cm (43–51 in).[8] Khối lượng khoảng 22,7 đến 45,4 kg (50 đến 100 lb)[chuyển đổi: số không hợp lệ] và thay đổi theo giới tính, với con trống nặng hơn con mái. Đây là loài chim còn sống nặng thứ năm trên thế giới, chỉ đứng sau các loài chim chạy.[9] Khối lượng của loài cũng thay đổi theo mùa, như chim cánh cụt trống và mái mất một khối lượng đáng kể trong khi nuôi con non và ấp trứng. Một con trống phải chịu đựng cái rét ở Nam Cực trong hơn 2 tháng để bảo vệ trứng của nó. Trong thời gian này, con trống không hề ăn gì cả. Hầu hết con trống sẽ giảm 12 kg (26 lb) trong khi nó chờ cho con non nở.[10] Khối lượng trung bình của con trống vào đầu mùa sinh sản là 38 kg (84 lb) và của con mái là 29,5 kg (65 lb)[chuyển đổi: số không hợp lệ]. Sau mùa sinh sản, cả con mái và con trống sẽ giảm khoảng 23 kg (51 lb).[11][12][13]

Like all penguin species, emperor penguins have streamlined bodies to minimize drag while swimming, and wings that are more like stiff, flat flippers.[14] The tongue is equipped with rear-facing barbs to prevent prey from escaping when caught.[15] Males and females are similar in size and colouration.[11] The adult has deep black dorsal feathers, covering the head, chin, throat, back, dorsal part of the flippers, and tail. The black plumage is sharply delineated from the light-coloured plumage elsewhere. The underparts of the wings and belly are white, becoming pale yellow in the upper breast, while the ear patches are bright yellow. The upper mandible of the 8 cm (3 in) long bill is black, and the lower mandible can be pink, orange or lilac.[16] In juveniles, the auricular patches, chin and throat are white, while its bill is black.[16] Emperor penguin chicks are typically covered with silver-grey down and have black heads and white masks.[16] A chick with all-white plumage was seen in 2001, but was not considered to be an albino as it did not have pink eyes.[17] Chicks weigh around 315 g (11 oz) after hatching, and fledge when they reach about 50% of adult weight.[18]

The emperor penguin's dark plumage fades to brown from November until February (the Antarctic summer), before the yearly moult in January and February.[16] Moulting is rapid in this species compared with other birds, taking only around 34 days. Emperor penguin feathers emerge from the skin after they have grown to a third of their total length, and before old feathers are lost, to help reduce heat loss. New feathers then push out the old ones before finishing their growth.[19]

The average yearly survival rate of an adult emperor penguin has been measured at 95.1%, with an average life expectancy of 19.9 years. The same researchers estimated that 1% of emperor penguins hatched could feasibly reach an age of 50 years.[20] In contrast, only 19% of chicks survive their first year of life.[21] Therefore, 80% of the emperor penguin population comprises adults five years and older.[20]

Vocalisation[sửa | sửa mã nguồn]

As the species has no fixed nest sites that individuals can use to locate their own partner or chick, emperor penguins must rely on vocal calls alone for identification.[22] They use a complex set of calls that are critical to individual recognition between parents, offspring and mates,[11] displaying the widest variation in individual calls of all penguins.[22] Vocalizing emperor penguins use two frequency bands simultaneously.[23] Chicks use a frequency-modulated whistle to beg for food and to contact parents.[11]

Adaptations to cold[sửa | sửa mã nguồn]

The emperor penguin breeds in the coldest environment of any bird species; air temperatures may reach −40 °C (−40 °F), and wind speeds may reach 144 km/h (89 mph). Water temperature is a frigid −1,8 °C (28,8 °F)[chuyển đổi: số không hợp lệ], which is much lower than the emperor penguin's average body temperature of 39 °C (102 °F). The species has adapted in several ways to counteract heat loss.[24] Dense feathers provide 80–90% of its insulation and it has a layer of sub-dermal fat which may be up to 3 cm (1,2 in) thick before breeding.[25] While the density of contour feathers is approximately 9 per square centimetre (58 per square inch), a combination of dense afterfeathers and down feathers (plumules) likely play a critical role for insulation.[26][27] Muscles allow the feathers to be held erect on land, reducing heat loss by trapping a layer of air next to the skin. Conversely, the plumage is flattened in water, thus waterproofing the skin and the downy underlayer.[28] Preening is vital in facilitating insulation and in keeping the plumage oily and water-repellent.[29]

The emperor penguin is able to thermoregulate (maintain its core body temperature) without altering its metabolism, over a wide range of temperatures. Known as the thermoneutral range, this extends from −10 đến 20 °C (14 đến 68 °F). Below this temperature range, its metabolic rate increases significantly, although an individual can maintain its core temperature from 38,0 °C (100,4 °F)[chuyển đổi: số không hợp lệ] down to −47 °C (−53 °F).[30] Movement by swimming, walking, and shivering are three mechanisms for increasing metabolism; a fourth process involves an increase in the breakdown of fats by enzymes, which is induced by the hormone glucagon.[31] At temperatures above 20 °C (68 °F), an emperor penguin may become agitated as its body temperature and metabolic rate rise to increase heat loss. Raising its wings and exposing the undersides increases the exposure of its body surface to the air by 16%, facilitating further heat loss.[32]

Adaptations to pressure and low oxygen[sửa | sửa mã nguồn]

Mounted skeleton at the American Museum of Natural History

In addition to the cold, the emperor penguin encounters another stressful condition on deep dives—markedly increased pressure of up to 40 times that of the surface, which in most other terrestrial organisms would cause barotrauma. The bones of the penguin are solid rather than air-filled,[33] which eliminates the risk of mechanical barotrauma.

While diving, the emperor penguin's oxygen use is markedly reduced, as its heart rate is reduced to as low as 15–20 beats per minute and non-essential organs are shut down, thus facilitating longer dives.[15] Its haemoglobin and myoglobin are able to bind and transport oxygen at low blood concentrations; this allows the bird to function with very low oxygen levels that would otherwise result in loss of consciousness.[34]

Distribution and habitat[sửa | sửa mã nguồn]

The emperor penguin has a circumpolar distribution in the Antarctic almost exclusively between the 66° and 77° south latitudes. It almost always breeds on stable pack ice near the coast and up to 18 km (11 mi) offshore.[11] Breeding colonies are usually in areas where ice cliffs and icebergs provide some protection from the wind.[11] Three land colonies have been reported: one (now disappeared) on a shingle spit at the Dion Islands on the Antarctic Peninsula,[35] one on a headland at Taylor Glacier in Victoria Land,[36] and most recently one at Amundsen Bay.[4] Since 2009, a number of colonies have been reported on shelf ice rather than sea ice, in some cases moving to the shelf in years when sea ice forms late.[37]

The northernmost breeding population is on Snow Island, near the northern tip of the Peninsula.[4] Individual vagrants have been seen on Heard Island,[38] South Georgia,[39] and occasionally in New Zealand.[13][40]

The total population was estimated in 2009 to be at around 595,000 adult birds, in 46 known colonies spread around the Antarctic and sub-Antarctic; around 35% of the known population lives north of the Antarctic Circle. Major breeding colonies were located at Cape Washington, Coulman Island in Victoria Land, Halley Bay, Cape Colbeck, and Dibble Glacier.[41] Colonies are known to fluctuate over time, often breaking into "suburbs" which move apart from the parent group, and some have been known to disappear entirely.[4] The Cape Crozier colony on the Ross Sea shrank drastically between the first visits by the Discovery Expedition in 1902–03[2] and the later visits by the Terra Nova Expedition in 1910–11; it was reduced to a few hundred birds, and may have come close to extinction due to changes in the position of the ice shelf.[42] By the 1960s it had rebounded dramatically,[42] but by 2009 was again reduced to a small population of around 300.[41]

Conservation status[sửa | sửa mã nguồn]

In 2012 the emperor penguin was uplisted from a species of least concern to near threatened by the IUCN.[1][43] Along with nine other species of penguin, it is currently under consideration for inclusion under the US Endangered Species Act. The primary causes for an increased risk of species endangerment are declining food availability, due to the effects of climate change and industrial fisheries on the crustacean and fish populations. Other reasons for the species's placement on the Endangered Species Act's list include disease, habitat destruction, and disturbance at breeding colonies by humans. Of particular concern is the impact of tourism.[44] One study concluded that emperor penguin chicks in a crèche become more apprehensive following a helicopter approach to 1.000 m (3.300 ft).[45]

Population declines of 50% in the Terre Adélie region have been observed due to an increased death rate among adult birds, especially males, during an abnormally prolonged warm period in the late 1970s, which resulted in reduced sea-ice coverage. On the other hand, egg hatching success rates declined when the sea-ice extent increased; chick deaths also increased; The species is therefore considered to be highly sensitive to climatic changes.[46] In 2009, the Dion Islands colony, which had been extensively studied since 1948, was reported to have completely disappeared at some point over the previous decade, the fate of the birds unknown. This was the first confirmed loss of an entire colony.[47]

Halley Bay Colony in 1999

Beginning in September 2015, a strong El Niño, strong winds, and record low amounts of sea ice resulted in "almost total breeding failure" with the deaths of thousands of emperor chicks for three consecutive years within the Halley Bay colony, the second largest emperor penguin colony in the world. Researchers have attributed this loss to immigration of breeding penguins to the Dawson-Lambton colony 55 km (34 mi) south, in which a tenfold population increase was observed between 2016 and 2018. However, this increase is nowhere near the total number of breeding adults formerly at the Halley Bay colony.[48]


A Woods Hole Oceanographic Institution study in January 2009 found that emperor penguins could be pushed to the brink of extinction by the year 2100 due to global climate change. The study constructed a mathematical model to predict how the loss of sea ice from climate warming would affect a big colony of emperor penguins at Terre Adélie, Antarctica. The study forecasted an 87% decline in the colony's population, from three thousand breeding pairs in 2009 to four hundred breeding pairs in 2100.[49]

In June 2014 a study by the Woods Hole Oceanographic Institution concluded that emperor penguins are at risk from global warming, which is melting the sea ice. This study predicted that by 2100 all 45 colonies of emperor penguins will be declining in numbers, mostly due to loss of habitat. Loss of ice reduces the supply of krill, which is a primary food for emperor penguins.[50]

Behaviour[sửa | sửa mã nguồn]

Emperor penguin colony

The emperor penguin is a social animal in its nesting and its foraging behaviour; birds hunting together may coordinate their diving and surfacing.[51] Individuals may be active day or night. A mature adult travels throughout most of the year between the breeding colony and ocean foraging areas; the species disperses into the oceans from January to March.[13]

The American physiologist Gerry Kooyman revolutionised the study of penguin foraging behaviour in 1971 when he published his results from attaching automatic dive-recording devices to emperor penguins. He found that the species reaches depths of 265 m (869 ft), with dive periods of up to 18 minutes.[51] Later research revealed a small female had dived to a depth of 535 m (1.755 ft) near McMurdo Sound. It is possible that emperor penguins can dive for even deeper and longer periods, as the accuracy of the recording devices is diminished at greater depths.[52] Further study of one bird's diving behaviour revealed regular dives to 150 m (490 ft) in water around 900 m (3.000 ft) deep, and shallow dives of less than 50 m (160 ft), interspersed with deep dives of more than 400 m (1.300 ft) in depths of 450 đến 500 m (1.480 đến 1.640 ft).[53] This was suggestive of feeding near or at the sea bottom.[54]

Both male and female emperor penguins forage for food up to 500 km (311 mi) from colonies while collecting food to feed chicks, covering 82–1.454 km (51–903 mi) per individual per trip. A male returning to the sea after incubation heads directly out to areas of permanent open water, known as polynyas, around 100 km (62 mi) from the colony.[53]

An efficient swimmer, the emperor penguin exerts pressure with both its upward and downward strokes while swimming.[55] The upward stroke works against buoyancy and helps maintain depth.[56] Its average swimming speed is 6–9 km/h (3,7–5,6 mph).[57] On land, the emperor penguin alternates between walking with a wobbling gait and tobogganing—sliding over the ice on its belly, propelled by its feet and wing-like flippers. Like all penguins, it is flightless.[14] The emperor penguin is a very powerful bird. In one case, a crew of six men, trying to capture a single male penguin for a zoo collection, were repeatedly tossed around and knocked over before all of the men had to collectively tackle the bird, which weighs about half as much as a man.[58]

As a defence against the cold, a colony of emperor penguins forms a compact huddle (also known as the turtle formation) ranging in size from ten to several hundred birds, with each bird leaning forward on a neighbour. As the wind chill is the least severe in the center of the colony, all the juveniles are usually huddled there. Those on the outside upwind tend to shuffle slowly around the edge of the formation and add themselves to its leeward edge, producing a slow churning action, and giving each bird a turn on the inside and on the outside.[59][60]

Predators[sửa | sửa mã nguồn]

Emperor penguin attacked by a leopard seal

The emperor penguin's predators include birds and aquatic mammals. Southern giant petrels (Macronectes giganteus) are the predominant land predator of chicks, responsible for over one-third of chick deaths in some colonies and they scavenge dead penguins as well. The south polar skua (Stercorarius maccormicki) mainly scavenges for dead chicks, as the live chicks are usually too large to be attacked by the time of its annual arrival in the colony.[61] Occasionally, a parent may attempt to defend its chick from attack, although it may be more passive if the chick is weak or sickly.[62]

The only known predators thought to attack healthy adults, and who attack emperor penguins in the water, are both mammals. The first is the leopard seal (Hydrurga leptonyx), which takes adult birds and fledglings soon after they enter the water.[63] Orcas (Orcinus orca), mostly take adult birds, although they will attack penguins of any age in or near water.[62]

Courtship and breeding[sửa | sửa mã nguồn]

Although Emperor penguins can breed at around three years of age, they generally don't begin breeding for another one to three years.[18] The yearly reproductive cycle begins at the start of the Antarctic winter, in March and April, when all mature emperor penguins travel to colonial nesting areas, often walking 50 đến 120 km (31 đến 75 mi) inland from the edge of the pack ice.[64] The start of travel appears to be triggered by decreasing day lengths; emperor penguins in captivity have been induced successfully into breeding by using artificial lighting systems mimicking seasonal Antarctic day lengths.[65]

The life-cycle of the emperor penguin

The penguins start courtship in March or April, when the temperature can be as low as −40 °C (−40 °F). A lone male gives 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; it then moves around the colony and repeats the call. A male and female then stand face to face, with one extending its head and neck up and the other mirroring it; they both hold this posture for several minutes. Once in pairs, couples waddle around the colony together, with the female usually following the male. Before copulation, one bird bows deeply to its mate, its bill pointed close to the ground, and its mate then does the same.[66]

Contrary to popular belief, Emperor penguins do not mate for life; they are serially monogamous, having only one mate each year, and remaining faithful to that mate. However, fidelity between years is only around 15%.[66] The narrow window of opportunity available for mating appears to be an influence, as there is a priority to mate and breed which usually precludes waiting for the previous year's partner to arrive at the colony.[67]

The egg of the emperor penguin. It is 13.5 × 9.5 cm and vaguely pear-shaped. Muséum de Toulouse

The female penguin lays one 460–470 g (1,01–1,04 lb) egg in May or early June;[66] it is vaguely pear-shaped, pale greenish-white, and measures around 12 cm × 8 cm (4+3⁄4 in × 3+1⁄4 in).[64] It represents just 2.3% of its mother's body weight, making it one of the smallest eggs relative to the maternal weight in any bird species.[68] 15.7% of the weight of an emperor penguin egg is shell; like those of other penguin species, the shell is relatively thick, which helps minimize risk of breakage.[69]

After laying, the mother's food reserves are exhausted and she very carefully transfers the egg to the male, and then immediately returns to the sea for two months to feed.[64] The transfer of the egg can be awkward and difficult, especially for first-time parents, and many couples drop or crack the egg in the process. When this happens, the chick inside is quickly lost, as the egg cannot withstand the sub-freezing temperatures on the icy ground for more than one to two minutes. When a couple loses an egg in this manner, their relationship is ended and both walk back to the sea. They will return to the colony next year to try mating again. After the female departs for the sea and the male takes charge of their egg, he spends the dark, stormy winter incubating the egg in his brood pouch, balancing it on the tops of his feet, for around 65-75 consecutive days until hatching.[66] The emperor penguin is the only species where this behaviour is observed; in all other penguin species both parents take shifts incubating.[70] By the time the egg hatches, the male will have fasted for around 120 days since arriving at the colony.[66] To survive the cold and savage 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. In the four months of travel, courtship, and incubation, the male may lose as much as 20 kg (44 lb), from a total mass of 38 đến 18 kg (84 đến 40 lb).[71][72]

Hatching may take as long as two or three days to complete, as the shell of the egg is thick. Newly hatched chicks are semi-altricial, covered with only a thin layer of down and entirely dependent on their parents for food and warmth.[73] The chick usually hatches before the mother's return, and the father feeds it a curd-like substance composed of 59% protein and 28% lipid, which is produced by a gland in his oesophagus.[74] This ability to produce "crop milk" in birds is only found in pigeons, flamingos and male Emperor penguins.The father is able to produce this crop milk to temporarily sustain the chick for only about one week, until the mother returns from fishing at sea with food to properly feed the chick. If the mother penguin is delayed, the chick will die. [75] The young chick is brooded in what is called the guard phase, spending time balanced on its parent's feet and sheltered in the brood pouch.[73]

Emperor penguin feeding a chick

The female penguin returns at any time from hatching up to ten days afterwards, from mid-July to early August.[64] She finds her mate among the hundreds of fathers by his vocal call and takes over caring for the chick, feeding it by regurgitating the partially digested fish, squid and krill that she has stored in her stomach. The male is often reluctant to surrender the chick he has been caring for to its mother, but he soon leaves to take his turn at sea, spending 3 to 4 weeks feeding there before returning.[64] The parents then take turns, one brooding while the other forages at sea.[66] If either parent is delayed or fails to return to the colony, the lone parent will return to the sea to feed, leaving the chick to die.[76] Abandoned eggs do not hatch and orphaned chicks never survive. Female emperors who failed to find a mate to breed with, or have lost their own chick may attempt to adopt a stray chick or steal the chick of another female. The mother of the chick and neighboring females will fight to protect the chick or reclaim it, if it has been successfully stolen. These scuffles involving several birds often result in the chick being smothered or trampled to death. Chicks which have been adopted or stolen are quickly abandoned once again, as the female is unable to feed and care for the chick alone. The parentless chicks wander around the colony attempting to seek food and protection from other adults. They will even try to shelter themselves in an adult bird's brood pouch already occupied by their own chick. These stray chicks are brusquely driven away by the adults and their chicks. All orphaned chicks will rapidly become weaker and die of starvation, or freeze to death.[77][78][79]

About 45–50 days after hatching, the chicks form a crèche, huddling together for warmth and protection. During this time, both parents forage at sea and return periodically to feed their chicks.[73] A crèche may comprise up to several thousand chicks densely packed together and is essential for surviving the low Antarctic temperatures.[80]

From early November, chicks begin moulting into juvenile plumage, which takes up to two months and is usually not completed by the time they leave the colony. Adults cease feeding them during this time. All birds make the considerably shorter trek to the sea in December and January. The birds spend the rest of the summer feeding there.[63][81]

Feeding[sửa | sửa mã nguồn]

The emperor penguin's diet consists mainly of fish, crustaceans and cephalopods,[82] although its composition varies from population to population. Fish are usually the most important food source, and the Antarctic silverfish (Pleuragramma antarcticum) makes up the bulk of the bird's diet. Other prey commonly recorded include other fish of the family Nototheniidae, the glacial squid (Psychroteuthis glacialis), and the hooked squid species Kondakovia longimana, as well as Antarctic krill (Euphausia superba).[54] The emperor penguin searches for prey in the open water of the Southern Ocean, in either ice-free areas of open water or tidal cracks in pack ice.[11] One of its feeding strategies is to dive to around 50 m (160 ft), where it can easily spot sympagic fish like the bald notothen (Pagothenia borchgrevinki) swimming against the bottom surface of the sea-ice; it swims up to the bottom of the ice and catches the fish. It then dives again and repeats the sequence about half a dozen times before surfacing to breathe.[83]

Relationship with humans[sửa | sửa mã nguồn]

In zoos and aquariums[sửa | sửa mã nguồn]

Two Adélie penguins and an emperor penguin at SeaWorld San Diego

Since the 1930s, there have been several attempts at keeping emperor penguins in captivity, but until the 1960s these attempts were unsuccessful, as knowledge of penguin keeping in general was limited and acquired by trial and error. The first to achieve a level of success was Aalborg Zoo where a chilled house was built especially for this Antarctic species. One individual lived for 20 years at the zoo and a chick was hatched there, but died shortly after.[84]

Today, the species is kept at just a few zoos and public aquariums in North America and Asia. Emperor penguins were first successfully bred at SeaWorld San Diego; more than 20 birds have hatched there since 1980.[85][86] Considered a flagship species, 55 individuals were counted in captivity in North American zoos and aquaria in 1999.[87] In China, the emperor penguin was first bred at Nanjing Underwater World in 2009,[88] followed by Laohutan Ocean Park in Dalian in 2010.[89] Since then it has been kept and bred at a few other facilities in China, and the only confirmed twin emperor penguins (the species normally lays just one egg) hatched at Sun Asia Ocean World in Dalian in 2017.[90] In Japan, the species is housed at Port of Nagoya Public Aquarium and Wakayama Adventure World, with successful hatching at Wakayama.[91]

Penguin rescue, rehabilitation and release[sửa | sửa mã nguồn]

In June 2011, a juvenile emperor penguin was found on the beach at Peka Peka, north of Wellington in New Zealand. He had consumed 3 kg (6,6 lb) of sand, which he had apparently mistaken for snow, as well as sticks and stones, and had to undergo a number of operations to remove these to save his life. Following recovery, on 4 September, the juvenile, named "Happy Feet" (after the 2006 film), was fitted with a tracking device and released into the Southern Ocean 80 km (50 mi) north of Campbell Island.[92][93] However, 8 days later scientists lost contact with the bird, suggesting that the transmitter had fallen off (considered likely) or that he had been eaten by a predator (considered less likely).[94]

Cultural references[sửa | sửa mã nguồn]

The species' unique life cycle in such a harsh environment has been described in print and visual media. Apsley Cherry-Garrard, the Antarctic explorer, wrote in 1922: "Take it all in all, I do not believe anybody on Earth has a worse time than an emperor penguin".[95] Widely distributed in cinemas in 2005, the French documentary La Marche de l'empereur, which was also released with the English title March of the Penguins, told the story of the penguins' reproductive cycle.[96][97] The subject has been covered for the small screen five times by the BBC and presenter David Attenborough: first in episode five of the 1993 series on the Antarctic Life in the Freezer,<ref>{{cite episode| title = The Big Freeze| series = Life in the Freezer| airdate = 1993| season = 1| number = 5|network= BBC|credit

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