There are 17 species of penguins in the world and they have various qualities in common. They are all found in the southern hemisphere, although one species, the Galapagos penguin, actually ranges a few miles north of the equator. However, in spite of what most people believe, less than half of the penguin species actually live in Antarctic waters.
Penguins are the most aquatic of the sea birds, and they generally spend most of their lives at sea (except when molting or rearing young). All penguins are flightless and adapted for life in cold water, so even those found in the low latitudes are dependent upon cold water currents for their livelihood.
The wings of penguins are much reduced, but are stiff, flat, tapered, and pointed in order to propel the birds through the heavy medium of water almost as though they were flying. They swim by flapping their wings underwater rather than paddling with their feet. Penguins are evolved from flying ancestors and have very well-developed pectoral muscles attached to a large keel on the sternum, like aerial flyers, which facilitates their being fast and powerful swimmers. They have taken ecological niches unfilled by flying birds.
Except for the feet and perhaps bare patches on the face, the entire body is covered with small, dense, overlapping, scale-like feathers, and there is a downy tuft at the base of each feather which increases the heat retention abilities even more. Feathers account for about 80% of the penguins' insulative properties, while fat provides the other 20%. Penguins have very high internal body temperatures (about 38° C, or 101° F), as well as high metabolic rates. With all this taken into account it is easy to understand how the Antarctic species in particular can survive, and even thrive, in a cold, harsh climate.
Penguins have dense, solid bones, and no air sacs, in order to counteract buoyancy, and they float very low at the water's surface. Their bodies are very streamlined, so the animals expend little energy for either floating or submerging. Most penguins can submerge for five to seven minutes, but the largest species (the emperor penguin) can submerge for up to 18 minutes. Studies have shown the emperor penguin can dive to at least 265 m (875 ft), but most other species do not normally go deeper than about 70 m (230 ft). The maximum speed quoted for penguins in the water is usually exaggerated, because their small size makes them appear faster than they really are. The maximum speed is probably about 24 km/hr (15 mph).
Being marine predators, adult penguins exhibit the typical marine predator color design…a dark dorsal surface and a light ventral surface. The are slight variations on this theme, but this countershaded pattern makes it more difficult for their prey and their predators to detect them when they are in the water.
Although the various penguin species obviously have many similarities, they constitute four different genera (Spheniscus Eudyptes Aptenodytes and Pygoscelis)that have evolved slightly different patterns of behavior. During our expeditions to Antarctica and southern-most South America, we generally observe penguins from all four groups, often as many as eight species.
In Tierra del Fuego and the Falkland Islands, we can see the Magellanic (Spheniscus magellanicus), rockhopper (Eudyptes crestatus), and king (Aptenodytes patagonica) penguins. The Magellanic penguin is of the group most people are familiar with in public oceanaria…the little man in the tuxedo. It is a rather small, black and white animal that grows to a length of about 70 cm (28 in). Like all members of this genus, it has a prominent black band that crosses the chest and extends down the two flanks, as well as a white stripe around each cheek and a pinkish bare patch of exposed skin near each eye that is used for thermoregulation.
The rockhopper penguin is in the crested penguin group and has two very obvious narrow bands of yellow feathers that extend from the base of the red, stout bill over the eyes and off to the sides as loose plumes. Otherwise, they are the basic black and white penguin design. It is a small penguin that stands less than 60 cm (24 in). The rockhopper penguin typically nests on steep, rocky shorelines with direct access to the sea, although the chosen sites often involves a lengthy, difficult climb to reach, which forces it to hop on the rocks and boulders…hence the appealing name.
King penguins were once very numerous in the Falkland Islands, but they were nearly extirpated in the 19th and early 20th centuries for their oil. A few colonies have become reestablished in recent decades, but their numbers are still very low here. It is a very large animal that can be 100 cm (about three feet) in length. The king penguin is a very colorful and attractive animal with a dark,bluish-gray back, white front with a yellow-orange throat patch and an orange, upside-down, teardrop-shaped marking on each side of the black head. The beak is long, curved, and pointed.
Around the Antarctic Peninsula, we commonly see gentoo (Pygoscelis papua), Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis Antarctica), emperor (Aptenodytes forsteri), and rarely Macaroni (Eudyptes chrysolophus) penguins. The Pygoscelid or brush-tailed penguins are all really quite similar in their markings and habits, but they are easily differentiated. The gentoo is the largest of this group and stands about 80 cm (32 in) tall. It is a basic black and white penguin, but has a prominent white triangular patch above each eye and brilliant orange-red markings on either side of the beak, and a black throat. It is interesting to note that this species is the least common of the Antarctic penguins, but has been spreading farther southward in the peninsular region within recent years, probably because of the increase in average temperature, extended breeding season, and less sea ice now found there.
Adélie penguins are entirely black and white, with no bright colorful markings.It does have an obvious white ring around the eye, as well as black throat. It reaches a length of about 65 cm (about 25 in). This species commonly forms huge colonies during the breeding season, often numbering in the hundreds of thousands.
The Chinstrap penguin is very similar to the Adélie penguin in markings and size, except the adult chinstrap has a white throat with a thin black line delineating the bottom edge of where the black throat marking would be…if it were similar to an Adélie. Like the Adélie, this species also commonly forms huge colonies…sometimes numbering in hundreds of thousands or even millions.
Sighting the emperor penguin is always an exciting event. This is the largest penguin, standing at nearly 120 cm (about four ft), and is usually encountered singly or in small groups on sea ice. It is closely related to the king penguin and has a somewhat similar appearance, although it is much more massive for its size than the king. It also has a similar marking and color scheme compared to the king penguin, but the colors are more subdued. Most of the individuals we see resting on ice flows are juveniles and have not yet attained their brightest coloration.
On South Georgia, we can see king (A. patagonica), gentoo (P. papua), chinstrap (P. Antarctica), and Macaroni (Eudyptes chrysolophus) penguins. The Macaroni penguin is a boisterous, scrappy little crested penguin that looks very much like the rockhopper penguin, except the Macaroni’s crest is gold in color, and considerably thicker. This is the commonest penguin in Antarctica, but it typically places its colonies along steep, rocky shorelines (like the rockhopper), usually on isolated, storm-tossed islands that make observation somewhat difficult.