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Emperor Penguins

 
 

This article is of particular interest to Capgo's Development Manager, Graham Henstridge. Graham spent his formative professional years in Antarctica, as an Electronics Engineer responsible for geophysical, glaciological and biological instrumentation and monitoring projects.

Emperor Penguins are one of the most amazing animals on the planet and one of the most adaptive, both in terms of their breeding habits and their ability to adjust to cold climate conditions.

Breeding

Each year, close to midwinter, the adult females will return to the rookery where they where born. This journey is likely to involve a walk of 50 to 200 km over sea-ice, possibly is blizzard conditions. These rookeries, numbering only 35 in total, are distributed around the harsh coast of Antarctica. While most animals choose spring or summer to begin their breading cycle, the Emperor Penguins have developed a cycle that requires them to begin 'nesting' when temperatures can be as low as -45°C (excluding wind chill).


Antarctic sea ice in the crisp midday twilight beside Taylor Glacier. With temperatures
of -30°C, the Emperors cover great distances over this magnificent icescape.

A single large egg is laid in mid-May and is passed to the male to incubate for the remaining 65 days. The female returns to sea to feed. Just before the male hatches the egg in mid-July, the female returns to take over the nurturing of the chick. The male returns to sea (another 100 km journey) after around 115 days of fasting and a 45% loss in body weight.

The females feed the chick for six weeks on reserves before the males return again. At seven weeks, the chicks are able to join a crèche of chicks, allowing the parents to share feeding responsibility. In January, the chicks and adults moult, and, with their new plumage move northwards with the sea-ice breakout in February.

It is believed this timing has evolved to ensure the young chicks are able to feed independently and close to the nesting site, when the food supply peaks in January.

Cold climate adaptations

To deal with the extended time in extreme cold, the Emperor Penguin has developed a number of physiological and behavioural adaptations:

  • A thick and relatively stiff 30 mm layer of feathers that provide the primary insulation. This layer is mechanically strengthened by short, strong feathers, ensuring relative immunity to ruffling (and hence heat loss) by all but the strongest of winds. The temperature gradient across this feather layer can be as much as 60°C.
  • A layer of blubber or fat, that provides additional insulation, although its main role is as an energy store. The temperature drop across this layer is typically no more than 5°C.
  • An efficient body shape, with a relatively low surface area to volume ratio.
  • A highly developed counter current heat exchange vascular system, that allows the skin and appendage temperatures to be lowered without, excessive heat loss.
  • Efficient metabolism, which allows a low breathing rate, to reduce heat loss through the lungs. An elaborate heat exchanger system in the nasal passages, which also reduces heat loss by using the heat of exhalation to warm incoming air.
  • To reduce the impact of wind, a sheltered site is selected for the rookery. However, site selection is not that simple, for a completely sheltered site will allow wind driven drift snow to settle. Therefore sites require sufficient wind scouring to prevent drift snow build-up.
  • The Emperor Penguins always stands in the cold, even though the prone position is probably the more stable and comfortable. This prevents the feather layer being squashed, which would significantly reduce its effectiveness as insulation. Further, while standing, the emperors rests back on its tarsi or heels to minimise the ground contact area.
  • In the cold, the Emperor Penguins will stand in a compact huddle, whether in a group of ten or many hundreds of birds. This social thermo-regulation reduces the total exposed surface area of the group and the total heat loss by up to 40%. Each penguin leans forward on a neighbour. The outside birds tend to face into the huddle and move slowly forward and induce a slow churning action. This churning gives all birds a turn on the inside, and the benefits of this behaviour.
  • The incubating egg is placed on the feet and completely covered with an inverted brooding pouch. In a huddle, this location is near optimal. Avoiding the need to build a nest also saves energy.
  • Emperor Penguins are very tolerant birds with no defined territory. They also mate for life. This behaviour is both energy and time efficient.
No other animal has such a highly developed set of cold weather survival skills as the Emperor Penguin. Some animals of the arctic region come close, but their strategy is the escape the cold by hibernation in snow caves or by migration.

Interesting Emperor Penguin Facts

  • The Emperor Penguin has been recorded diving to depths of 535 meters and for staying submerged for up to 22 minutes. This information was obtained from a small data logger fitted with a pressure sensor mounted on the leg of an Emperor Penguin.
  • A well fed Emperor Penguin weighs in at around 40kg. By the time the male bird has incubated the egg and returned to sea, its weight may be as low as 20kg.
  • Emperor Penguin eggs are large - about 120mm long and weighing 600gm. They take about 65 days to incubate.
  • While a little clumsy on land, the Emperor Penguin is a fast and agile swimmer, capable of speeds of up to 40kph.
  • On land the adult Emperor Penguin has no predators. In the water, the Emperor is a popular meal for the Leopard Seal and the Killer Whale.
  • There are believed to be about 400,000 Emperor Penguins in the 35 known rookeries in Antarctica.