Penguins in the southern hemisphere

Many times at zoos and aqariums, polar bears and penguins are found displayed next to one another, but don't be fooled into believing that penguins and polar bears actually live together in the wild. Polar bears live in the far north and penguins reside in the southern hemisphere. Within the southern hemisphere they occur over a wide range of latitudes, from the equator to 78°S. Different penguin species are found along the coasts of South America, Africa, Australia, New Zealand, Antarctica, and on a number of Antarctic islands. Because they cannot fly, penguins must live in areas where food is plentiful and reliable in nearby waters.

The Southern Ocean:
The Southern Ocean is an ideal home for penguins because of the year-round abundance of food provided by the important ocean process of upwelling.

Water Flow:
The Southern Ocean is full of cold water that continually circles Antarctica in an easterly direction. Water circulation is driven by fierce winds, and as the water travels, it flows around over a dozen island clusters surrounding Antartica.

Upwelling:
Upwelling occurs when water from below the surface layer of the ocean rises to the surface and brings with it nutrients such as phosphate, nitrate, and silicate. These nutrients are taken up by microscopic algae, called diatoms, which combine the nutrients with energy absorbed from sunlight in order to grow. Diatoms serve as a rich food source for green plankton organisms, which make up the base of the ocean's food pyramid. Ocean areas rich in diatoms and plankton support large numbers of all organisms that are higher up on the food chain. For example, krill, the favorite food of many penguin species, feed heavily on diatoms.

Upwelling Locations:
Upwelling occurs wherever surface waters move away from coastlines. In the southern hemisphere, this occurs in many areas inhabited by penguins. Where the circumpolar current hits the southern tips of Africa and South America, the current splits and streams up the western coast of the two continents. Along South America, the current which moves water offshore is called the Humboldt Current and along Africa, it is called the Benguela Current. These two nutrient rich currents support three species of penguins. The Antarctic Convergence, which encircles the Antarctic continent between 50 and 60 degrees south, is also another location where penguins reside. At this site, cold Antarctic waters combine with warm, salty waters of the Atlantic, Indian, and Pacific oceans causing sinking and mixing of water that brings nutrients to the surface.

Penguins and Upwelling:
Upwelling is necessary for penguin survival because nutrient rich upwelled waters generate plankton and diatoms, which support krill and fish that penguins feed on. The importance of upwelling to penguins can be observed during El Niño periods and is part of the reason why penguins can survive in the southern hemisphere.

El Niño:
Scientists know that upwelling is important to penguin survival because during episodes when upwelling is greatly decreased, like during El Niño, many penguins die of starvation. A strong El Niño from October 1982-July 1983 reduced the population of Galapagos penguins by 77%. An El Niño episode brings warm water southward along the coast of South America, preventing cold water upwelling in areas offshore of Peru, Chile, and the Galapagos Islands. This change causes plankton production to drop, resulting in a decline in plankton and fish that feed penguins.

Northern vs. Southern Hemisphere:
Upwelling made it possible for penguins to become flightless birds in the southern hemisphere in the course of evolution. While the northern hemisphere does have many upwelling sites, they are highly unpredictable and change locations as the wind and ocean currents move. This unpredictable nature of northern upwelling sites means that sometimes food sources are located very far from land. In order to reach large distant food sources, penguins would sometimes need to travel distances farther than those journeyed in the southern hemisphere. Since chick survival is directly related to how long a parent must spend away from the nest foraging, chick survival would decline in the northern hemisphere because of long parent absences. This is compared to the southern hemisphere, where travel distances are more or less constant from season to season. With this high risk to survival in the northern hemisphere, it is clear that penguins adapted to the southern hemisphere, where they could be assured greater success in raising young.

Birds in the North:
Penguins do not live in the northern hemisphere, but this does not mean that other swimming birds are absent there. Swimming and diving birds that live in the northern hemisphere are part of the auk family. They can survive in the face of unpredictable food sources because they, unlike penguins, can fly.

Auks:
There are 22 kinds of auks in the northern hemisphere and they live in colonies, swim, dive, eat the same food, and look similar to penguins. These similarities make this group of birds the ecological equivalent of the penguin in the north. Members of the auk family are birds like puffins, murres, and auklets, which are often mistaken for penguins. In fact, murres are often referred to as the "northern penguin".

Flight:
Despite similar appearance and behaviors, auks differ from penguins because they can fly. Flight allows these birds to undertake long journeys to upwelling sites without the risk of being absent from the nest for too long. While auks are are not the best or furthest flyers because their wings are so small, they can at least fly for brief periods, which takes less energy than swimming. Flight allows auks to survive in the northern hemisphere and the only way penguins could do the same would be to learn how to fly.