Emperor penguins: winter survivors
Facts
Emperor penguins are truly amazing birds. They not only survive the Antarctic winter, but they are capable of breeding during the worst weather conditions on earth. The emperor is the largest of the 17 penguin species growing up to 1.15m tall and weighing up to 40kg. There are approximately 195 000 pairs of emperors breeding in some 35 colonies along the Antarctic coast. Emperors usually breed on the frozen sea and link their breeding cycle to the annual setting and breaking up of the ice.
Emperors are near the top of the Southern Ocean's food chain. They eat fish, squid and krill, which are also harvested by man. Emperors are the deepest divers of any bird. They can dive to an astounding 565m and have the ability to stay under water for up to 22 minutes. They seem clumsy on land but when they are in water, their shape gives them great agility. They are also very strong birds and their strength and agility make them very effective predators.
Facts
Emperor penguins are truly amazing birds. They not only survive the Antarctic winter, but they are capable of breeding during the worst weather conditions on earth. The emperor is the largest of the 17 penguin species growing up to 1.15m tall and weighing up to 40kg. There are approximately 195 000 pairs of emperors breeding in some 35 colonies along the Antarctic coast. Emperors usually breed on the frozen sea and link their breeding cycle to the annual setting and breaking up of the ice.
Emperors are near the top of the Southern Ocean's food chain. They eat fish, squid and krill, which are also harvested by man. Emperors are the deepest divers of any bird. They can dive to an astounding 565m and have the ability to stay under water for up to 22 minutes. They seem clumsy on land but when they are in water, their shape gives them great agility. They are also very strong birds and their strength and agility make them very effective predators.
Special adaptations to the cold
Nature has provided the emperor with excellent insulation in the form of four layers of scale-like feathers that not even a blizzard can disorganise. They have a very small bill and flippers which conserve heat. Their nasal chambers also recover much of the heat that is normally lost during exhalation. Emperor penguins have large reserves of energy-giving body fat and a low level of activity during winter. They are also very social creatures, and one of their survival mechanisms is an urge to huddle together to keep warm. This huddling instinct means that they do not defend any territory. The emperor penguin is the only species of penguin that is not territorial.
Another special adaptation of the emperor penguin is the ability to "recycle" its own body heat. The emperor's arteries and veins lie close together so that blood is pre-cooled on the way to the bird's feet, wings and bill and warmed on the way back to the heart.
Emperor's feet are adapted to the icy conditions, since they have strong claws for gripping the ice. They also have folds of feathers for holding the egg during incubation
The male “mother”
The emperor has not only evolved special physical characteristics to help it survive the extreme Antarctic conditions, it has also developed some unique social features. Like most penguins, emperor parents closely share parental duties. What is unique about emperors however, is the co-operation between males while carrying out their parenting duties.
The male emperor endures a 115-day ordeal, during which he courts, mates and incubates an egg without eating a single meal. Along with this, he has to cope with wind chill temperatures reaching down to minus 60ºC. The males conserve their energy by huddling together to keep warm.
The female lays her egg in mid-May, then leaves to spend the winter at sea. The male spends the next 65 days with the egg resting on his feet enveloped in a patch of naked skin on his lower abdomen. The egg's incubation chamber is completed by an abdominal fold that is lowered over the egg.
Breeding begins in March and ends in December. This allows the parents to fledge their chicks during summer when the weather is warmer and food is abundant
Huddling
Emperor penguins have to face freezing winds called katabatic winds, which blow off the polar plateau and intensify the cold. Emperor colonies also face blizzards of up to 200km/h. To keep warm, the males close ranks to share their warmth. Emperors are big birds, when carrying their incubation fat, they are about as large around the chest as a man. Yet on very cold days, as many as 10 of them pack into every square metre of a huddle. In the huddle, individuals seem to temporarily lose their identity, and the mass of emperors takes on the appearance and behaviour of a single living entity. On a functional level, huddling cuts the heat loss by as much as 50%, and enables males to survive the long incubation fast since the warmer they are, the longer their fat lasts. The temperature inside a huddle can be as high as + 35 degrees celsius.
On a social level, huddling behaviour is an extraordinary act of co-operation in the face of a common hardship, and emperors take this act of group co-operation to its extreme, they take turns to occupy the warmest and coldest positions in the huddle. On windy days, those on the windward edge feel the cold more than those in the centre and down-wind. One by one they peel off the mob and shuffle, egg on feet, down the flanks of the huddle to rejoin it on the lee. They follow one another in a continuous procession, passing through the warm centre of the huddle and eventually returning back to the windward edge. Because of this constant circulation the huddle gradually moves downwind. During a 48 hour blizzard, the huddle may shift as much as 200 m.
Hatching and growing
In mid-July, when the female returns, she finds her mate by having memorised his call. The male carefully transfers the egg to the female in about ten seconds. The egg hatches soon after the egg is transferred to the female. An egg or chick accidentally tipped on the snow and abandoned can freeze to death in two minutes. The male then starts the long trip to open water and food. When he feeds again, it will be the first time he has eaten in nearly four months.
Emperor chicks grow quickly because they have only five months to reach the stage where they can fend for themselves. Male and female parents take turns to travel to the sea and return to feed the chick. It takes so long to get to the sea and back that both parents between them can only manage 16 meals in the entire five months of incubating the egg and raising the chick. It is not surprising that meals are enormous. Feeds can be up to 30% of the chick's body weight, which is equivalent to a 60kg person eating 18kg in one sitting!
- Wendy Rockliffe, Graham Robertson, Australian Antarctic Division
