Emperor penguins (Aptenodytes forsteri) are the most well-known penguins living in Antarctica– they star in March of the Penguins and are one of the continent’s best examples of adaptation to its extreme environment. They are the largest species of penguin, reaching up to 122 cm (48 inches) tall and weighing from 22-45 kg (49-99 lb), although they weigh only 11 ounces at birth. During the rearing of their young, males and females lose weight because they are incubating eggs and caring for their offspring instead of feeding themselves– in fact, males lose an average of 15 kg (33 lb)– almost 40% of their body weight! Males will fast for 4 months while the females are out foraging for food (Williams 1995); when females return to take over caring for the newly hatched chick, males travel up to 100 km across the ice before they reach water, where they can finally find their food. There are many risks to a young penguin, and fewer than 20% survive their first year (Williams 1995).
When penguins molt, their new feathers coming in are not initially waterproof, so the penguins cannot swim until the feathers have gained their waterproof coating. During this time, since they are unable to hunt for food, they must conserve energy, and they become quiescent for weeks on end. They do not move even when people are nearby. During our stay at McMurdo, four emperor penguins found their way to the road near Pegasus, the landing strip, and stationed themselves there during their molt. Because they were just off the road, we could see them closely when driving by. Of course, we are still not allowed to approach them, and must maintain a distance great enough that they hardly notice us. Fortunately, I have a nice zoom lens!
Emperor penguins breed on the sea ice during the Antarctic winter (they are the only penguin species to brave the harsh winter during their breeding season), which makes it difficult for scientists to locate penguin colonies. In the winters, temperatures reach -50 C and winds can reach up to 200 km per hour! During this time, males huddle together in huge groups so that they are somewhat sheltered from the wind. They take turns being on the outside of the huddle and then rotate in towards the protected center. Conditions are inhospitable, but breeding during the coldest part of the year assures that chicks will be born to more favorable weather, and will be more likely to survive. Colonies may move from year to year, so monitoring them over time is problematic. Furthermore, without knowing the number and location of colonies, it is difficult to assess how penguins are responding to climate change, overfishing, and other environmental changes. So how can we estimate where breeding colonies are found? By looking for penguin poo. Scientists are actually able to find penguin colonies from space by locating guano stains in the snow by satellite!
Emperor penguins are highly adapted to living in such cold environments: they have four layers of feathers and large fat stores to keep them warm. They store extra fat above their feet where they keep the egg and hatched chick– this can keep the egg at a constant temperature, sometimes up to 70 degrees C warmer than outside! They also have a circulatory system in which arterial blood traveling towards the feet and flippers is cooled by venous blood running towards the body’s core. By first cooling the blood before it reaches the feet, this maintains the feet at a cooler temperature than the rest of the body, and excessive heat loss by feet touching the ice is avoided. Cold air they breathe is warmed as soon as in enters the body in much the same way, but passing closely by warm air coming out.
Penguins are adept swimmers and divers–they can dive down to 550 meters (over 1650 feet)! They can even stay there for over 20 minutes while they forage for food. This is astounding for several reasons, one of which is the sheer amount of pressure created at such depths: even at depths of just 366 meters (1200 feet), pressure exerted is equal to 40 times that at the surface (Owen 2004). This means air in the lungs is restricted to 1/40 the volume on land! Scientists have determined some of the reasons why penguins can dive so deep, although not all adaptations for the process are known.
Penguins’ bones are solid, without the large air pockets found in other birds’ bones. This prevents direct damage to the bones. Penguins can remain deep underwater because of a special type of hemoglobin that functions at low oxygen levels. While diving, penguins’ body temperature remains the same, but their heart rate can decrease to 15 beats per minute! This reduces their metabolism so they do not need to consume as much oxygen (which is less abundant at great depths). Furthermore, penguins cut off blood supply to all non-essential organs, which not only conserves oxygen, but also prevents nitrogen levels in the blood from rising to dangerous levels. These adaptations can be studied for use in medical practice in humans; for example, during heart attacks, oxygen supply to organs is cut off, and understanding how bodies deal with depleted oxygen may improve health of heart attack survivors (Owen 2004).
Emperor penguin fun facts: Their preferred food is fish, but they will also eat krill and squid. They have backwards-facing barbs on their tongues to prevent prey from escaping. They have sophisticated communication systems which allow for individual identification of young and mates. At 100 feathers per square inch, they have the highest feather density of any bird species (Hile 2004). Like many species in polar regions, emperors may be sensitive to changes in climate because of their dependence on sea ice.
sources: British Antarctic Survey 2009. Scientists map penguins from space by locating their feces. ScienceDaily. Accessed February 23, 2010 at http://www.sciencedaily.com/releases/2009/06/090602122621.htm.
Cherel, Y. and F. Freby 1994. Daily body mass loss and nitrogen excretion during molting fast of macaroni penguins. The Auk 111 (2): 492-495.
Dewey, T. 1999. “Aptenodytes forsteri” (On-line), Animal Diversity Web. Accessed February 12, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Aptenodytes_forsteri.html.
Drisdelle, R. 2006. How do penguins keep warm? http://birds.suite101.com/article.cfm/how_do_penguins_keep_warm_
Hile, J. 2004. Emperor penguins: uniquely armed for Antarctica. National Geographic Channel, http://news.nationalgeographic.com/news/2004/03/0329_040329_TVpenguins.html
Le Maho, Y.; P. Delclitte, and J Chatonnet (1976). “Thermoregulation in fasting emperor penguins under natural conditions”. Am. J. Physiol. 231 (3): 913–922.
Aptenodytes forsteri, Emperor Penguin – MarineBio.org. Retrieved Saturday, February 27, 2010, from http://marinebio.org/species.asp?id=534.
Owen, J. 2004. “Penguin Ranch” reveals hunting, swimming secrets. National Geographic Society.
Williams 1995. The penguins.