Emperor Penguins
Aptenodytes forsteri

Emperor penguins have the upright and regal bearing that their name suggests. They take the dinner-jacketed formality of all penguins to its highest level and though they are able to be as awkward, gawky and get as dirty as other penguins, when they shake it all off and stand up to regain their dignity, there are few if any more stately and elegant animals on earth.

Emperor penguins are the largest of penguin species with an average weight of around 30kg (66lb, but can be up to 40kg (88lb)) and a height of approx. 1.15m (3.8ft).

They have colourful feathers around their necks and heads, though are not quite as bright as king penguins which are almost as large. There is little or no possibility of confusing the two species however as their distribution around Antarctica is very different. While king penguins are a sub-Antarctic species, being based on islands dotted around the continent, emperor penguins are animals of the deep south.

Emperor penguins have yellow ear patches that are "open" fading into the white of the breast feathers, whereas king penguins have orange ear patches that are "closed" by a band of black feathers. Emperor penguin chicks have distinctive plumage with a large white face patch.

All but 2 of about 40 known emperor penguin colonies are on winter fast ice that is frozen solid and attached to the land from autumn until it begins to break up in the spring (though some years it doesn't break up at all). They are found all around the coasts of the Antarctic continent. They breed during the depths of the Antarctic winter and in some of the most desolate, coldest, windiest and downright grim places on the planet during the season of 24 hour darkness. Some emperor penguins are therefore the only birds that never set foot on land.

The first breeding colony wasn't discovered until 1902 by Lt. Reginald  Skelton on Scott's 1901-04 Discovery Expedition some 130 years after the birds had first been seen on Captain Cook's second voyage. New colonies were still being discovered as late as 2009.

Early in the 20th century, Emperor penguins were thought to be some kind of evolutionary "missing link", something that scientists thought could be proven by observing the growth of the embryo at various stages. On Scott's 1910-1913 Terra Nova expedition a small group of expeditioners set out on a winter sledging journey led by Wilson, the biologist and including the young Apsley Cherry-Garrard, famously this gave rise to the acknowledged greatest of all Antarctic adventure and travel books "The Worst Journey in the World".

Emperor penguins feed on fish, krill and squid which they catch on dives that are longer and deeper than any other penguin or bird species. They can dive to a depth of 1,800 feet (550 meters) and hold their breath for up to 22 minutes. This allows them to reach and exploit food resources that other birds can't reach.

The diving abilities of emperor penguins has been widely studied, they have been found to have:

1/ an increased ability to store oxygen in the body
2) the ability to tolerate low levels of oxygen in the body
3) the ability to tolerate the effects of pressure.

Emperor penguins tolerate low levels of oxygen during dives that would cause a human to pass out and they experience pressures so great that we would get the bends. Neither of these things seem to adversely affect penguins. Their diving physiology is studied at McMurdo Station  at a place called penguin ranch 15 miles out in the sea ice where there is only a single hole in the ice, so the penguins must return there to leave the sea.

A penguin's normal resting heart-beat is about 60-70 beats per minute (bpm), this goes up to 180-200 bpm before a dive as they load up with oxygen, then as they hit the water, the rate drops to 100 bpm immediately slowing to only 20 bpm during most of the dive so they use the stored oxygen in blood and muscles to the maximum effect. On returning to the surface again, the heart rate goes back to 200 bpm probably to pay back the "oxygen debt" they have incurred during the dive.

March of the penguins to the breeding site
photo Warner Bros

Emperor penguins with chicks under the brood-patch, one can just be seen emerging
photo Warner Bros

Emperor Penguins, Family, Antarctica
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They begin their breeding cycle when other Antarctic penguins have finished theirs, at the end of April to May. Other smaller penguins at this time head north away from the encroaching winter while the Emperors head south into it. They seem to choose very dramatic sites, a large flat area where they can waddle when carrying their egg or chick on their feet surrounded by high ice cliffs or icebergs that help to give a little shelter from the winds.

Eggs are laid in May and June, they are the smallest relative to body size of any bird, being around 0.4kg (1.1lb) just under 1.5% of the mass of an adult bird.

At this point, the males take charge of the egg. No nest is built and the egg is incubated on the feet of the parents, a special fold of abdominal skin covers the egg to keep it warm. The mother penguins then set off back to sea and do not return until July.

The male Emperors with their valuable eggs sit huddled together on the ice throughout the dark weeks and months of the Antarctic night. The average temperature is around -20°C (-4°F) going down to -50°C (- 58°F) and with winds that gust up to 200km per hour (124mph). The males do not eat at all throughout this time, but just sit and wait and protect their egg, (later the chick) until their mate comes back to relieve them.

Very few people have seen an emperor penguin huddle in the winter in a savage place where ice and cold are king and the penguins spend days in silence. The only events are changing position in the huddle (see below) and the immense spectacle of the ghostly red, violet and green of the southern lights or Aurora australis playing in the dark skies above their heads.

Males can be sat incubating and waiting for over 120 days (average 115), during this time they will lose about 40% of their body weight.  They use less energy when asleep which they do so as long as possible, it is not unusual for emperor penguins to sleep for 20 or more hours a day under these conditions - even up to 24 hours a day, to conserve their food supplies and increase their and their chick's chances of survival.

They survive by huddling together for warmth, very unusual behaviour for adult penguins which are usually aggressively territorial. They also take it in turns to occupy the coldest most exposed outside positions. Without this huddling behaviour, they would unable to endure the combined conditions of fasting, bitter cold and hurricane force winds and would not be able to live and breed in the way they do.

It's not all altruistic behaviour though, and taking it in turns. The ones that have been on the outside on the windward side wander off to the leeward side when they've had enough so exposing the next "layer" of penguins. The whole huddle can wander over quite an area in this way in very cold and/or windy conditions.

Emperor Penguins, Chick Being Brooded
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Emperor penguin parents and chicks, the chicks are now able to regulate their own temperature in milder conditions and don't need the protection of the brood patch. They form creches and will huddle as the parents do if the weather worsens
photo Warner Bros

Eventually, the female emperor returns across the sea ice. This usually coincides with the hatching of the chick. Sometimes the chick will hatch before the female returns, if this happens, it will be fed with a secretion of protein and fat produced by the male from its oesophagus a sort of penguin "milk".

The pair locate each other by calling repeatedly, eventually recognizing each others voice, and the male passes the chick over (sometimes reluctantly and after much persuasion) onto the feet of the female. A chick left alone on the ice at this time has a survival time of only around two minutes. The males are then able to go off to sea to feed and build up their strength and fitness again. This journey alone can take several days across the ice. Emperor penguins have been known to walk 280km to reach the sea.

At this point, the chick is reared in the conventional penguin manner, with the parents taking it in turns to feed and look after the chick until they are large enough to leave.

The chicks then huddle together in "creches" for warmth and protection while both parents are able to go off to collect food at the same time to provide for the ever increasing needs of the growing chick.

Chick survival has a lot to do with how the ice breaks up and so how easy it is for parents to reach the sea. If the parents have to travel long distances, many chicks will die of starvation. If the ice edge remains close, then the parents will be able to provide more food and the chicks stand a better chance of survival.

The colonies begin to disperse as the sea ice begins to break up in December and January, the chicks are then able to fend for themselves leaving the adults to moult their feathers ( a time when they stay out of the water) and so are not able to feed.

The chicks are very large too compared to other penguin species, if they were reared in the summer, they would have to be left to fend for themselves at a time of the year when food supply is reducing. As the chicks food requirement is very high, this would cause major problems.

With this breeding strategy, the penguin chicks become independent during the height of the summer food supply and so are able to survive better.

Emperor penguins are able to raise a chick each year by this strategy, though the rigorous conditions of life in the deep south mean that only 19% of chicks will survive their first year. King penguins on the other hand can expect an 80% first year survival rate, though their breeding strategy means that they rear 2 chicks every 3 years and the requirement for open water year-round restricts their range to sub-Antarctic islands.

Emperors are preyed upon by Killer Whales, Leopard Seals, and the Giant Petrel. The most dangerous predator is the Leopard Seal that can eat about 15 penguins a day though they usually only catch the weak or the very sick. Healthy penguins can usually out-swim a Leopard Seal.

There were estimated to be around 238,000 breeding pairs of emperor penguins in the world in 2009. Taking into consideration the non-breeder ratio as well this translates into about 595,000 adult birds. Emperor penguins reach breeding age at 4 years and can live to be 20.