The North Rockhopper Penguin (Eudyptes moseleyi) is a penguin species that breeds only on seven islands in the South Atlantic and Indian Oceans, and therefore has a limited distribution. These islands include Tristan da Cunha, Gough, Amsterdam and Saint Paul. The main concentration of the global population is observed on Tristan da Cunha and Gough Islands. According to recent global assessments, the total number of individuals is estimated to be approximately 270,000 pairs. When examining current data on the islands, it was reported that in 2009 there were 83,000 pairs on Middle Island, 25,000 pairs on Nightingale, 54,000 pairs on Inaccessible, and 6,700 pairs on Tristan. The 2006 estimate for Gough Island is 64,700 pairs. In addition, there are 24,890 pairs on Amsterdam Island and 9,023 pairs on St. Paul Island, which belongs to France, in the South Indian Ocean. ^【1】  This species was previously considered to be the same species as the southern rockhopper penguin (Eudyptes chrysocome) based on genetic analyses conducted in 2006, but has since been classified as a separate species due to morphological and behavioural differences.

Morphological Characteristics and Systematic Position

Physical Description

The Northern Rockhopper Penguin (Eudyptes moseleyi) averages 42–45 cm in length and weighs 2.4–4.3 kg, making it smaller than other rockhopper penguin species. Its body structure is covered with black feathers on the head and back, and white feathers on the abdomen and chest. It has a reddish ring around the eyes, a feature that distinguishes it from other rockhopper penguin species. Its beak is orange-reddish in colour and thicker and heavier in males than in females.

A striking feature of the Northern Rockhopper Penguin is the long, yellow and black feathered ‘punk’ crown-like structure on its head. These feathers reflect the species' name, ‘rockhopper’, facilitating their movement by hopping across rocky terrain. Young individuals have black back and white belly feathers similar to adults, with pale eyes and beaks. Over time, the yellow feathers on their heads become more prominent and they take on their adult form.

Taxonomy and Evolution

The genus Eudyptes is the most diverse genus of penguins, with between 6 and 8 extant species. Rockhopper penguins are divided into three main groups: E. moseleyi, which inhabits warm subtropical waters, and E. chrysocome and E. filholi, which inhabit cold sub-Antarctic waters. Molecular phylogenetic studies indicate that E. moseleyi diverged from the E. chrysocome and E. filholi species approximately 3 million years ago. This divergence developed in parallel with the species' adaptation processes to different ocean currents and marine ecosystems.

The fossil records of the genus Eudyptes shed light on the evolutionary history of the species. For example, the species Eudyptes atatu lived approximately 3.2 million years ago and is considered the earliest known species of this genus. The existence of this species indicates that the evolutionary history of rockhopper penguins dates back a long time and that they diversified over time by adapting to different ecosystems.

^{Northern Rockhopper Penguin (Pixabay)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The Northern Rockhopper Penguin (Eudyptes moseleyi) is a penguin species with a limited distribution, breeding only on seven islands in the South Atlantic and Indian Oceans. These islands include Tristan da Cunha, Gough, Amsterdam and Saint Paul. The species' breeding grounds are located between 37° and 40° south latitude. During the breeding season, the Northern Rockhopper Penguin builds its nest at sea level or on rocky slopes. On Gough Island, nests are found on open rocky beaches, while on Nightingale and Inaccessible Islands, they are located under dense, tall grass cover. Materials such as grass, twigs, feathers, and stones are used to build the nest.

It spends much of its marine life in the 30 km of coastal waters surrounding its breeding colonies. Most dives occur at depths of 10–25 metres and last between 90 and 120 seconds. During these dives, it feeds on marine life such as krill, fish, squid and octopus. During the breeding season, the Northern Rockhopper Penguin travels from the sea to land to reach its breeding grounds. Males usually arrive before females and settle in the breeding areas. The social structure and behaviour of the species play an important role during mating and the care of the young. 

Nutritional Ecology

A large part of their diet consists of marine life such as krill, small fish, squid and octopus. However, small pelagic fish such as sardines and anchovies also feature among the fish species they consume. These prey are preferred, especially during periods when stocks are abundant. Northern Rock Penguins typically catch their prey by swimming in the middle and upper parts of the water column. This strategy aims to dominate fish shoals, compressing the prey and directing it towards the water surface. This makes catching prey more efficient. Adult Northern Rock Penguins usually perform synchronised dives in loose flocks of 20 to 200 individuals during feeding. These cooperative dives enable the prey to be compressed and directed towards the water surface, allowing each individual to obtain more prey per unit of time.

Reproductive Biology

Northern Rockhopper Penguins gather in colonies for breeding. These colonies are typically found in rocky areas and regions up to 170 metres above sea level. The breeding season may vary depending on the geographical location of the colonies. For example, in the colonies on the Tristan da Cunha archipelago, the breeding season begins in late July or early August. They return to the same nest each year to breed, indicating that the species is monogamous and that pairs form long-term bonds.

Northern Rockhopper Penguins lay two eggs each breeding season. The first egg is usually small, while the second is large and heavy. The laying process can take approximately four to five days, during which the female incubates the first egg after laying it and then lays the second egg. The incubation period is usually 32 to 34 days, during which both parents take turns incubating the eggs. The second egg is usually laid before the first, and this plays a role in the growth process of the chicks.

Baby penguins are protected by only one parent during the first few weeks after hatching. During this period, feeding and protecting the chicks requires great care. At the end of the first month, the chicks gather in groups called ‘nurseries’. During this period, the chicks' social interactions increase and the parents go out to sea for long periods to feed. The chicks leave the nest after approximately 10 weeks. This process marks the period when the chicks gain independence and adapt to life at sea.

Although penguins appear to be extremely well adapted to life at sea, they are dependent on land for reproduction, raising their young, and moulting.^【2】 During the annual moulting period, which lasts approximately 25 days, Northern Rock Penguins cannot hunt or feed because they remain on land; sufficient fat reserves are important during this process. During moulting, old feathers are shed and new feathers grow. ^【3】 This process enables penguins to regain their waterproofing properties and thermoregulation (the ability of an organism to maintain its body temperature within certain limits, even if the ambient temperature varies) capacities. Moulting usually begins after the breeding season and plays a role in the species' survival strategies.

Conservation Status

The northern rockhopper penguin (Eudyptes moseleyi) was last assessed on the IUCN Red List of Threatened Species in 2020. The species is classified as Endangered due to a rapid decline in population over the last three generations (approximately 30 years), a limited distribution range, and increasing threats from land and sea. Although the exact causes of the decline are not fully understood, changes in the marine environment, such as rising sea temperatures, the decline or displacement of prey species, disease, and oil pollution, are thought to have contributed to this process.