Seventeen species of penguins live around the world, most in the cooler waters of the Southern Hemisphere. Body structure is similar among the species, but size varies. A little blue penguin (Eudyptula minor) weighs about 3 pounds, whereas an emperor penguin can reach 100 pounds or more. Penguins live on a seafood diet, which varies with the changes in seasons. Their remarkable diving abilities allow them to obtain seafood throughout the ocean.
Krill are very small shrimplike creatures, about 2 inches long, found throughout the Earth's oceans. Krill congregate in groups so large that they can be discerned from space. Most life forms in the Antarctic would disappear without krill in the ecosystem. Hundreds of different animals rely on krill as a dietary staple, including macaroni, Adelie and chinstrap penguins.
All penguins eat small fish, some more than others. Only about 4 percent of the chinstrap penguin's diet consists of fish. About 90 percent of an emperor penguin's diet is fish. They catch and eat fish with powerful beaks and backward-facing barbs of their tongues. Penguins favor small schooling fish like sardines, smelt, herring and anchovies.
Gentoo, emperor and rockhopper penguins, among others, eat squid as they become seasonally available. Squid are soft-bodied cephalopods with large brains, eight arms and two hearts. Penguins increase the number of squid they eat as the prey become more plentiful in the summer months. They eat juvenile squid and small squid including the arrow and the greater hooked.
Sometimes, penguins eat crustaceans, invertebrates with hard exoskeletons and segmented bodies and more than four pairs of jointed appendages. Shrimp, crab and sand hoppers are crustaceans. Adult penguins can dive as deep as 330 feet to retrieve small crustaceans, but they generally have to dive no deeper than around 150 to 165 feet.
Chinstrap penguins have been known to eat amphipods, which resemble shrimp. They do not have a hard covering over the thorax, unlike most crustaceans. Amphipods, a dominant fauna on the underside of sea ice, provide food for penguins, fish, seals and other birds. These tiny creatures inhabit nearly all aquatic habitats.
- British Antarctic Survey: Penguins
- New England Aquarium: Penguin Species
- National Geographic: Krill
- Penguin Husbandry Manual: Chapter 5, Diet and Nutrition
- University of Washington: Chinstrap Penguin
- University of Washington: Emperor Penguin
- Marine Education Society of Australasia: Crustaceans
- Encyclopedia Britannica: Chinstrap Penguin
- University of Florida: Amphipods
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Based in Michigan, Keri Gardner has been writing scientific journal articles since 1998. Her articles have appeared in such journals as "Disability and Rehabilitation" and "Journal of Orthopaedic Research." She holds a Master of Science in comparative medicine and integrative biology from Michigan State University.