Emperor penguins (Aptenodytes forsteri) and Adelie penguins (Pygoscelis adeliae) both belong to taxonomic family Spheniscidae. These flightless birds have adapted to become extremely agile and adept in the water. Many similarities exist between the two species, but they have a range of differences, too.
At first glance, emperor and Adelie penguins look similar. Both have that distinctive penguin shape, with long bodies, flipperlike wings and long beaks. They're both black on their backs, heads, wings and tails, and white on their breasts and stomachs. The main difference comes when comparing their relative sizes. Emperor penguins measure around 45 inches tall and weigh between 48 and 80 pounds. Adelie penguins measure roughly 27 inches tall and weigh between 8 and 11 pounds.
Both emperor and Adelie penguins live exclusively in the Antarctic. The largest populations of Adelie penguins can be found in the Ross Sea, whereas emperor penguins are rarely found outside the 66th and 78th latitudes. Adelie penguins tend to live on large, coastal ice shelves but move to ice-free beaches to make their nests. Emperor penguins, on the other hand, almost never nest on land, preferring to do so on ice platforms, sometimes as far as 50 miles from open water.
As both emperor and adelie penguins hunt in the ocean, their diets are fairly similar. Both species eat a range of fish, crustaceans, cephalopods and amphipods. The main difference is that emperor penguins tend to have a more varied diet. Adelie penguins feed primarily on krill, as this is an abundant food source in the areas in which they live. They also eat some Antarctic silverfish, lantern fish, squid and more.
Social Structure and Reproduction
Although not much is known about their social structure, both emperor and adelie penguins live in large colonies and are known to be extremely social creatures. Their colonies can contain thousands of members living and hunting together. During the breeding season, males and females of both species form monogamous pairs and raise their chicks together. Emperor penguins are likely to pair with different mates the next breeding season; only about 15 percent pair with the same mate the following year. Adelie penguins, meanwhile always breed with the same mate as long as they both return to the same nesting ground.