The southern rockhopper penguin (Eudyptes chrysocome) is the smallest species of rockhopper penguin and breeds on sub-Antarctic islands around Antarctica, particularly in areas such as the Falkland Islands, South Georgia, Heard Island, and Campbell Island. This species, which once had a population of 2.5 million individuals, is now reported to be rapidly declining and is listed as ‘Vulnerable’ on the IUCN Red List.

The feeding habits of rockhopper penguins are affected by climate change in the oceans. In particular, rising sea temperatures are affecting the food sources of these penguins, negatively impacting their breeding success. These threats necessitate measures to protect the species.

Morphological Characteristics and Systematic Position

Physical Description

The southern rockhopper penguin (Eudyptes chrysocome) is the smallest species of the rockhopper penguin genus. Adult individuals are recognized by their height, ranging from 41 to 58 cm, and body weight, ranging from 2 to 3.8 kg. The body structure is covered with grey-blue feathers on the head and back; the abdominal region is white. Bright yellow feathers starting just above the eyes and extending backwards are one of the most distinctive features of this species. Additionally, there are black, spiky feathers on the top of the head. The eyes are reddish-brown, the beak is orange-red, and the legs and feet are pinkish in color. Sexual dimorphism, i.e. physical differences between males and females, is not pronounced in this species. However, males are generally slightly larger than females.

The feathers of rockhopper penguins are waterproof and covered with a thick layer of oil. This feature allows them to stay underwater for long periods and survive in cold waters. Their wings are strong and rigid, providing propulsion while swimming. When moving on rocky terrain, they advance with a ‘hopping’ motion, unlike terrestrial penguins, which have earned them the name ‘rockhopper’. Overall, the southern rockhopper penguin is a species known for its colorful and striking plumage, compact build, and ability to survive in harsh environments.

Taxonomy and Evolution

The southern rockhopper penguin (Eudyptes chrysocome) is the smallest species of the rockhopper penguin genus (Eudyptes) and is currently represented by three distinct taxa: E. c. chrysocome (Falkland Islands and islands at the southern tip of South America), E. c. filholi (sub-Antarctic islands in the Indian and Pacific Oceans) and E. moseleyi (Tristan da Cunha and Gough Islands). Molecular phylogenetic analyses indicate that these three taxa diverged approximately 0.97 million years ago. This divergence may have developed in parallel with environmental factors such as changes in sea temperatures and differences in ocean currents. Fossil records indicate that the origin of rockhopper penguins dates back approximately 5–7 million years, to the Late Miocene epoch. This early evolutionary process laid the foundation for penguins' adaptation to ocean ecosystems.

^{Southern Rockhopper Penguins (Pexels)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The southern rockhopper penguin (Eudyptes chrysocome) forms colonies on rocky islands in the sub-Antarctic and southern oceans, particularly on the Falkland Islands, Heard Island, Macquarie Island, the Crozet Islands and Campbell Island. This species prefers to nest on steep slopes and rocky coastal strips in direct contact with the sea. Nesting areas are typically located at elevations of 0–100 metres above sea level and are mostly in direct contact with the sea. Colonies are concentrated in rocky areas and regions close to the sea.

Southern rockhopper penguins spend a large part of their marine life in coastal waters. Their average diving depths range from 10–25 metres, although some individuals can dive to depths of up to 100 metres. Dive durations are typically 30–120 seconds, but can extend to 171 seconds. These penguins leave their colonies in the morning and spend most of the day feeding at sea. Many individuals spend the night at sea after returning from the ocean, demonstrating the species' ability to hunt at night. While feeding, they search for food in underwater currents and on the ocean floor.

Nutritional Ecology

The southern rockhopper penguin (Eudyptes chrysocome) is an important part of marine ecosystems due to its feeding habits and foraging strategies. A large part of this species' diet consists of krill (especially Euphausia lucens), cuttlefish and other crustaceans. Fish consumption is low and generally includes cold-water fish such as Notothenia and Myctophidae. When foraging, Southern rockhopper penguins typically feed in areas close to the seabed, performing benthic dives. These dives involve horizontal movements along the seabed rather than vertical movements in the water column. This allows them to efficiently catch their prey by cornering them.

Group hunting also plays an important role in this species' feeding strategy. Individuals form loose flocks of 20–200 individuals and perform synchronised dives, herding their prey and dragging it to the water's surface. This cooperative hunting method increases the catch per unit time.

Reproductive Biology

The southern rockhopper penguin (Eudyptes chrysocome) is a monogamous species, continuing to breed with the same mate each year. The breeding season varies depending on the geographical location; for example, the breeding season begins in October in the Falkland Islands, while the date may differ in other regions. Pairs usually lay two eggs; the first egg is small and light, while the second egg is large and heavy. The B-egg usually hatches first. The incubation period varies between 32–34 days, and both parents participate in this process.

After hatching, the chick is protected by the father for the first 24–26 days; the mother feeds at sea during this time. At 24–26 days old, the chick enters the ‘nursery’ stage; during this period, both the male and female parents feed the chick. The pup leaves the nest after approximately 60–130 days and returns to the colony after 12–22 months of ocean migration, having acquired its adult plumage. During the annual moulting period, individuals fast on land for two to three weeks; sufficient fat reserves are important during this process.

Conservation Status

The southern rockhopper penguin (Eudyptes chrysocome) was last assessed on the IUCN Red List of Threatened Species in 2020. The species' populations have declined rapidly from their high abundance in the first half of the 20th century to the present day, showing a decline of over 30% in the last three generations. Although some colonies appear to have stabilised, mass mortality events, thought to be related to food availability issues linked to changes in water temperature, occur frequently enough to prevent population recovery. Consequently, the population trend is predicted to continue declining rapidly in the future, and the species is classified as Vulnerable.