Southern rockhopper penguin

 The southern rockhopper penguin (Eudyptes chrysocome) is a species of rockhopper penguin, that is sometimes considered distinct from the northern rockhopper penguin. It occurs in subantarctic waters of the western Pacific and Indian Oceans, as well as around the southern coasts of South America.

                                       

Rockhopper penguins are known to have complex foraging behaviors. Influenced by factors such as sea ice abundance, prey availability, breeding stage, and seasonality, rockhopper penguins must be able to adapt their behavior 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 away from their colonies when foraging. Females typically forage during the day in 11-12h 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 behaviors 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.

Description

This is the smallest yellow-crested, black-and-white penguin 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 southern rockhopper penguin group has a global population of roughly 1 million pairs. About two-thirds of the global population belongs to E. c. chrysocome which breeds on the Falkland Islands and on islands off Patagonia. These include most significantly Isla de los Estados, the Ildefonso Islands, the Diego Ramírez Islands and Isla Noir. E. c. filholi breeds on the Prince Edward Islands, the Crozet Islands, the Kerguelen Islands, Heard Island, Macquarie Island, Campbell Island, the Auckland Islands and the Antipodes Islands. Outside the breeding season, the birds can be found roaming the waters offshore 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.

Benthic and pelagic dives

Rockhopper penguins are known to employ two different types of dives when foraging, pelagic and benthic dives. Pelagic dives are typically short and relatively shallow and used very frequently. Benthic dives are much deeper dives near the seafloor (up to 100 m deep) that typically last longer and have longer bottom time. Penguins performing benthic dives typically only perform a few depth wiggles (changes in depth profile) at their maximum depth. at an average speed of range of 6.9–8.1 kilometres per hour (6,900–8,100 m/h). Although deeper dives tend to be a bit longer than shallow dives, foraging rockhoppers will minimize their travel time when performing benthic dives to gain maximum efficiency. Benthic dives in particular show a stronger correlation to full stomachs than pelagic dives. Emperor penguins, gentoo penguins, yellow-eyed penguins and king penguins also use this deep-dive technique to obtain food.

Prey availability is dependent on many factors, such as current climate and conditions of the area. Typically, females will bring back a majority of crustaceans and occasionally some fish for their young. The female's foraging success directly affects chick growth. If food is scarce, females are able to fast for very long periods of time and sometimes will only forage for the chick's benefit.

Dive limitations

Because foraging conditions and outcomes are so variable, several factors can limit foraging practices. The timing of breeding, incubation and brooding periods greatly affect foraging time, as females are unable to leave broods for long periods of time. Females during the brooding period will follow a much more fixed foraging schedule, leaving and returning to the colony at roughly the same time each day. When not in breeding season, females have much more variability in the length of foraging trips. If females have low energy levels because they are fasting while provisioning chicks, they may make several short foraging trips instead of one longer one.

While benthic dives are efficient and favorable for rockhoppers, they present physiological limitations such as limits in lung capacity, which affects duration of dives. The longest aerobic dive rockhoppers can perform is about 110 seconds long, but dives can last upwards of 180–190 seconds.