The emperor penguin (Aptenodytes forsteri) is the heaviest and tallest extant penguin species and is native to Antarctica.
The male and female are alike, both in size and plumage, reaching 39 in (100 cm) in length and weighing 49 – 99 lb (22 – 45 kg). Feathers of the back and head are black and sharply delineated from the pale-yellow breast, white belly, and bright-yellow ear patches.
Similar to all penguins, it is flightless, with a streamlined body and wings flattened and stiffened into flippers for a marine habitat. Its diets consist mainly of fishes and cephalopods, such as squid, and crustaceans, such as krill. While hunting, the species can remain submerged for around 20 minutes, diving to a depth of 1,755 ft (535 m).
It is the only known penguin that breeds during Antarctic winter and also treks 31 to 75 mi (50 to 120 km) over the ice to breeding colonies, which can contain several thousand individuals.
The female lays the egg and returns to the sea to feed while leaving the male to incubate the egg for two months. The lifespan of an emperor penguin in the wild is 20 years, although some reports indicate that few individuals may live up to 50 years.
Adult emperor penguins are 43 to 47 in (110 to 120 cm) in length, including tail and bill. The weight ranges from 50 – 100 lb (22.7 – 45.4 kg) and varies by sex, with females weighing less than males.
It is the fifth heaviest extant bird species. Most male emperors will lose around 26 lb (12 kg) while waiting for their eggs to hatch.
The mean weight of the weight of males at the start of the breeding season is 84 lb (38 kg), and that of females is 65 lb (29.5 kg). After the breeding season, the weight drops to 51 lb (23 kg) for both sexes.
Like other penguin species, emperor penguins have streamlined bodies to reduce drag while swimming and wings that are more like flat, stiff flippers. Males and females are similar in colouration and size.
The adult has deep black dorsal feathers, which covers the head, back, throat, chin, dorsal part of the flipper, and tail. The upper mandible of the 3 in (8 cm) long bill is black, and the lower mandible can be orange, pink, or lilac.
In juveniles, its bill is black, while the auricular patches, throat, and chin are white. Emperor penguins have blackheads and white masks and are typically covered with silver-grey down. Chicks weigh around 11 oz (315 g) after hatching.
During the Antarctic summer (November to February), the emperor penguin’s dark plumages fade to brown. The colour change occurs before the yearly moult in January to February.
Compared to other birds, moulting is rapid in emperor penguin, and it takes only around 34 days. The overall average lifespan of an emperor penguin is approximately 20 years, and the yearly survival rate has been measured at 95.1%.
Adaptation to cold
The emperor penguin is known to breed in the coldest habitat known to any bird species; air temperatures may reach -40 °F (-40 °C), and wind speeds may reach 89 mph (144 km/h). Water temperature is a frigid -1.8 °F (28.8 °C), which is lower than the average emperor penguin body temperature of 102 °F (39 °C).
Dense feathers provide 80 to 90% of its insulation and it also has a layer that contains sub-dermal fat, which may be up to 1.2 in (3 cm) thick before breeding.
While the density of contour feathers is 58 per square inch (9 per square centimeter), a combination of dense down feathers (plumules) and after feathers likely play a role in insulation.
The emperor penguin can maintain its core body temperature (thermoregulate) without altering its metabolism. It can thermoregulate over a wide range of temperatures, and this is known as the thermoneutral range, this extends from 14 – 68 °F (-10 – 20 °C).
If the temperature drops below the thermoneutral range, its metabolic rate will increase significantly, although an individual can regulate its core temperature from 100.4 °F (38.0 °C) down to -53 °F (-47 °C). Movement by walking, swimming, and shivering are three mechanisms for increasing metabolism.
Although emperor penguins reach sexual maturity and can breed at three years of age, they generally don’t begin breeding for another 1 to 3 years.
They start to breed at the start of the Antarctic winter, when all mature penguins travel to the colonial nesting areas, often walking 31 – 75 mi (50 – 120 km) inland from the edge of the pack ice.
Courtship starts in March or April when the temperature can be as low as -40 °F (-40 °C). The female penguin lays one 1.01 to 1.04 lb (460 to 470 g) egg in May or June. It is vaguely pale greenish-white, pear-shaped, and measures around 4 ¾ in × 3 ¼ in (12 cm x 8 cm).
After laying the egg, the mother returns to the sea to feed for two months because her food reserves are exhausted, but before that, she transfers the egg to the father.
The transfer of the egg can be difficult and awkward, especially for first-time parents, and many couples crack or drop the egg in the process.
When the egg is dropped, the chick inside is definitely lost, as the chick cannot withstand the sub-freezing temperature on the icy ground for more than 1 – 2 minutes. If a couple loses their egg, the relationship will instantly end, and both partners walk back to the sea.
By the time the egg hatches, the male will have starved for 120 days. To survive the cold and savage wind of up to 120 mph (200 km/h), the males huddle together and take turns in the middle of the huddle.
In the four months of courtship, travel, and incubation, the male may lose as much as 44 lb (20 kg), from a total mass of 84 – 40 lb (38 – 18 kg). Hatching may take as long as 2 – 3 days to complete, as the shell of the egg is very thick.
The chick hatches before the mother’s return, and the father feeds it a curd-like substance composed of 28% lipid and 59% protein, which is produced by a gland in the male oesophagus. This ability to produce crop milk in birds is only found in flamingos, pigeons, and male emperor penguins.
The father produces this crop milk to temporarily sustain the chick for about one week until the mother returns from the sea with food to feed the chick properly. If the mother takes too long, the chick will die. The young chick is brooded at its parent’s feet (this is also called the guard phase).
When the female returns, the male will be reluctant to release the chick he has been caring for to the female. After he releases the egg, he returns to the sea, spending 3 – 4 weeks feeding.
Both partners take turns, one brooding while the other hunts at sea. If one partner delays or fails to return, the brooding parent will return to the sea, leaving the chick to die.
Orphaned chicks never survive, and abandoned eggs do not hatch. Female emperor penguin who lost their chick or failed to find a mate to breed with may attempt to steal the chick of another female or attempt to adopt a stray chick.
The neighbouring females or the mother of the chick will reclaim or fight to protect the chick if it has been successfully stolen.
The scuffles between several birds often result in the chick being trampled or smothered to death. All orphaned chicks will rapidly become weaker and freeze to death or die of starvation.
About 45 to 50 days after hatching, all the chicks form a crèche, huddling together for protection and warmth. Starting from early November, the chicks begin to moult into juvenile plumage.
This transformation may last for two months. After the transformation, the adult stops feeding them.
The emperor penguin’s diet consists mainly of crustaceans, fish, and cephalopods, although its composition varies on the population. The most important food source for the emperor penguin is fish, most especially the Antarctic silverfish (Pleuragramma antarcticum).
Other sources of food include the glacial squid (Psychroteuthis glacialis), fishes of the family Nototheniidae, and Antarctic krill (Euphausia superb), as well as the hooked squid species (Kondakovia longimana).
One of its feeding strategies is to dive to around 160 ft (50 m), where it can easily find sympagic fish like the bald notothen (Pagothenia borchgrevinki) swimming at the bottom surface of the sea-ice.