By Devon Phelan
Geographic Range
Rockhopper penguins are found on islands in the southern ocean, such as the Falkland Islands. They occur farther north than many other penguin species.
Biogeographic Regions:
neotropical 
(native ); atlantic ocean (native ).
Habitat
Rockhopper penguins are found in high grasses called tussocks, where they make burrows and nest. As their name implies, they live on rocky shorelines.
These animals are found in the following types of habitat:
temperate ; terrestrial ; saltwater or marine .
Terrestrial Biomes:
savanna or grassland .
Aquatic Biomes:
coastal .
Physical Description
(70.4 to 105.6 oz)
(21.65 in)
Rockhopper penguins measure about 55 centimeters in length and weigh around 2.5 kilograms. These birds stand upright on two short feet. Their legs are set far back on the body. The waterproof coat, composed of feathers that average 2.9 centimeters in length, is white on the underside and bluish-black on the top. The head has bright yellow plumage on the brow; the yellow feathers extend along the sides. The top of the head has spiked black feathers. The wings are strong, stiff, narrow and flipper-like. Rockhopper penguins have tiny eyes.
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Sexual dimorphism: sexes alike.
Reproduction
Rockhopper penguins breed once yearly.
Mating calls, which are species specific, are called "ecstatic vocalization." This draws attention to the bird and announces its intentions. Penguins mate with the same partners from previous years. (Williams, 1981)
Mating systems:
monogamous .
Rockhopper penguins typically mate in the early spring or late summer, enabling the young to go to the sea in the mid-summer. They mate in vast colonies and lay up to two eggs, although sometimes pairs "adopt" a third egg. The first egg is usually 20-50% smaller than second one. The small egg is usually lost, although it is capable of maturing into a normal bird. Adopted eggs are also typically lost. After each egg is laid, it is turned over to the male who sits on it and keeps it in his brood pouch for the next four months until it hatches. (Williams, 1981)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous .
While the male penguin sits on the incubating egg, he is nourished by the female, or else he fasts for the entire period. If the female does not return with food for the chick once it has hatched, the male produces "penguin's milk" from his digestive system and regurgitates it for the baby.
Parental investment:
precocial ; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (protecting: male); pre-weaning/fledging (provisioning: male, female, protecting: male).
Lifespan/Longevity
The average lifespan of a rockhopper penguin is 10 years.
Behavior
Penguins are very sociable animals. It is very rare to see one alone. Rockhopper penguins are the most aggressive, as well as the most numerous, penguins. They hide their heads under their wing while they rest. Rockhopper penguins leave the breeding colony in late summer or fall and spend 3-5 months at sea, where they find food. Penguin wings are used exclusively for swimming, these sea birds do not fly.
Key behaviors:
natatorial ; diurnal ; motile ; territorial ; social ; colonial .
Communication and Perception
Their loud cry, "ecstatic vocalization", is used to announce their presence, attract a mate, or announce the boundaries of their territory. As well as vocalizing, these birds shake their heads and cause their yellow eyebrows to fly into a "halo" in order to attract a mate.
Food Habits
Rockhopper penguins eat primarily krill (Euphausiacea). They also eat squid and other crustaceans. They make daily trips to the sea to forage.
Primary Diet:
carnivore (eats non-insect arthropods).
Animal Foods:
fish; aquatic crustaceans.
Economic Importance for Humans: Positive
Penguins are a tourist attraction, and they are one of the main reasons people travel to the Falkland Islands and other habitats of these penguins.
Conservation Status
It is estimated that rockhopper penguins have undergone a decline of more than 30% in their total population size over the past 30 years. For this reason, they are classified as vulnerable by the IUCN. If the decline continues, they may be uplisted to endangered in the near future. Threats to rockhopper penguin populations include commercial fishing, which reduces the amount of available prey, and oil spills. (Bingham, 2002; BirdLife International, 2004; Ryan and Cooper, 1991)
Other Comments
Rockhopper penguins keep warm by their well-developed fat layer and system for maintaining heat.
Contributors
Devon Phelan (author), University of Michigan.
Tanya Dewey (editor), Animal Diversity Web, University of Michigan Museum of Zoology.
