Scientific name: Eudyptes chrysocome
Physical description and related species
Rockhopper penguins are the smallest of the crested penguins at between 2.3 and 2.7 kg. Males are larger than females.
There are curently three recognised subspecies, although some may be separate species. Their taxonomy is in doubt and requires further study.
Distribution and abundance
Rockhopper penguins are the most widespread of the crested penguin, with a circumpolar distribution. They are found on islands near the Antarctic Polar Front to those near the subtropical convergence in the South Atlantic and Indian Oceans.
Conservation status: vulnerable
At a number of sites (Falkland and Campbell Islands, Tristan da Cunha and the Antipodes) the populations have declined substantially. At Campbell Island the decline has been in tbe order of 94%. The speculated reason for these declines is rises in sea surface temperature (due to global warming) which has affected the prey stocks of rockhopper penguins.
The population at Macquarie Island is estimated to be in the order of 100,000 to 500,000 individuals. A thorough census is required to establish its true extent and whether it is similarly declining.
The population status of the species at other sites is largely unknown.
Rockhopper penguins are very similar in their breeding biology and foraging behaviour to the royal penguins, although have a slightly shorter breeding season.
Two eggs are laid, with the smaller first egg never producing a chick to fledging.
Rockhopper penguins are very synchronised in their breeding cycle both within a colony and across years. Males return to the island in mid-October and females a few days later. Nests are re-established (with most returning to the same nest sites and mates) and two eggs laid.
Females take the first incubation shift while males go to sea to forage after having fasted for approximately four weeks. On their return the females depart for a foraging trip. They return as the chicks hatch. Females provide all food for the chick when it is young and being guarded by the male, but once chicks enter a creche, both parents forage.
Chicks fledge at the end of February. At this time adults go to sea to fatten for the moult, which they undertake in early March. After finishing the moult they depart the island in late April.
Diet and feeding
Rockhopper penguins eat predominantly euphausiids, myctophid fish and squid. The prey types they eat overlap a great deal with royal penguins, but rockhopper penguins eat more euphausiids and fewer fish (euphausiids 58%, fish 23% and the remainder squid and other crustaceans). The diet also changes marginally over the breeding season, between colonies and years.
Rockhopper, like royal penguins, are migratory and depart Macquarie Island at the end of the breeding season. Where they go during this period is also unknown. During the breeding season they feed in the Polar Frontal Zone in similar waters to royal penguins, although they do not travel as far. The places they feed change with the stage in the breeding season.