The western rockhopper penguin (Eudyptes chrysocome) is a species of rockhopper penguin. It occurs in subantarctic waters around the southern coast of South America and nearby islands. The western rockhopper penguin was formerly considered to be conspecific with the eastern rockhopper penguin (Eudyptes filholi) of the western Pacific and Indian Oceans, with the combined species then known as southern rockhopper penguin. These two taxa together had previously also been considered conspecific with the northern rockhopper penguin (E. moseleyi).
Taxonomy
In 1743 the English naturalist George Edwards included an illustration and a description of the western rockhopper penguin in the first volume of his A Natural History of Uncommon Birds. Edwards based his hand-coloured etching on a preserved specimen owned by Peter Collinson. When in 1758 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the tenth edition, he placed the western rockhopper penguin with the red-billed tropicbird in the genus Phaethon. Linnaeus included a brief description, coined the binomial name Phaethon demersus and cited Edwards' work. The use of Linnaeus' binomial name was not adopted by later ornithologists, because he had already used the specific demersa for the African penguin which he placed with the wandering albatross in the genus Diomedea. The western rockhopper penguin was formally described in 1781 by the German naturalist Johann Reinhold Forster under the binomial name Aptenodytes chrysocome. The species is now placed in the genus Eudyptes that was introduced by the French ornithologist Louis Pierre Vieillot in 1816. The genus name combines the Ancient Greek eu meaning "fine" with dyptes meaning "diver". The specific epithet chrysocome is from the Ancient Greek khrusokomos meaning "golden-haired" (from khrusos meaning "gold" and komē meaning "hair"). The species is monotypic; no subspecies are recognised. It was formerly treated as conspecific with the eastern rockhopper penguin with the English name "southern rockhopper penguin" for the combined species. It is now considered as separate based on a molecular phylogenetic study published in 2021. The two species differ in their distribution; the western species is found in Cape Horn, South America and the Falkland Islands while its eastern counterpart occupies the Southern Indian and Pacific Ocean. The eastern rockhopper penguin can also be distinguished by its pink margins around the bill. The northern rockhopper penguin lives in a different water mass from the western and eastern rockhopper penguins, separated by the Subtropical Front, and differs genetically from them. Therefore, northern birds are also now separated, as E. moseleyi. The rockhopper penguins are closely related to the macaroni penguin (E. chrysolophus) and the royal penguin (E. schlegeli). Interbreeding with the macaroni penguin has been reported at Heard and Marion Islands, with three hybrids recorded there by a 1987–88 Australian National Antarctic Research Expedition.
Description
This is the smallest of the yellow-crested, black-and-white penguins in the genus Eudyptes. It reaches a length of 45–58 cm (18–23 in) and typically weighs 2–3.4 kg (4.4–7.5 lb), although there are records of exceptionally large rockhoppers weighing 4.5 kg (9.9 lb). It has slate-grey upper parts and has straight, bright yellow eyebrows ending in long yellowish plumes projecting sideways behind a red eye.
Ecology The western rockhopper penguin group has a global population of roughly 1 million pairs. It breeds on the Falkland Islands and on islands off Patagonia. Outside the breeding season, western rockhopper penguins can be found roaming the waters offshore from their colonies. These penguins feed on krill, squid, octopus, lantern fish, mollusks, plankton, cuttlefish, and mainly crustaceans. A rockhopper penguin named 'Rocky' in Bergen Aquarium in Norway lived to 29 years 4 months. It died in October 2003. This stands as the age record for rockhopper penguins, and possibly it was the oldest penguin known.
Behaviour
Their common name refers to the fact that, unlike many other penguins, which get around obstacles by sliding on their bellies or by awkward climbing using their flipper-like wings as aid, rockhoppers will try to jump over boulders and across cracks. This behaviour is by no means unique to this species however; the other "crested" penguins in the genus Eudyptes also hop around rocks. But the rockhopper's congeners occur on remote islands in the New Zealand region, whereas the rockhopper penguins are found in places that were visited by explorers and whalers since the Early Modern era. Hence, it is this particular species in which this behaviour was first noted.
Their breeding colonies are located from sea level to cliff-tops and sometimes inland. Their breeding season starts in September and ends in November. Two eggs are laid but only one is usually incubated. Incubation lasts 35 days and their chicks are brooded for 26 days.
Variation in foraging behaviour Rockhopper penguins are known to have complex foraging behaviour. Influenced by factors such as sea ice abundance, prey availability, breeding stage, and seasonality, rockhopper penguins must be able to adapt their behaviour to fit the current conditions. Rockhopper penguins employ different strategies according to their conditions. When making foraging trips, rockhoppers typically leave and return to their colonies in groups. One study showed they are known for going up to 157 km (98 mi) away from their colonies when foraging. Females typically forage during the day in 11–12 hour trips consisting of many dives, but they will occasionally forage at night. Night dives are typically much shallower than day dives. Dives typically last around 12h, but can be up to 15hrs, with penguins leaving the colony around dawn (04:00) and returning at dusk (19:00).
Rockhopper penguins employ different strategies and foraging behaviour depending on the climate and environment. A main factor is food location. Subantarctic penguins must dive for longer periods of time and much deeper in search of food than do species in warmer waters where food is more easily accessible.
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