The emperor penguin (Aptenodytes forsteri) on sea ice in Antarctica and is the largest of all penguin species. Its life cycle is closely linked to the harsh conditions of Antarctica and is notable for its unique breeding strategy, which occurs particularly in the middle of winter. Adult individuals can weigh over 40 kg and reach a height of approximately 120 cm. Although the total population of the species has remained relatively stable since the mid-20th century, accelerated climate change, sea ice melt and associated breeding habitat loss in recent decades pose a serious threat. Current estimates indicate approximately 230–280 thousand breeding pairs; since 2012, based on climate models and observations, the species has been listed as ‘Vulnerable’ (VU) on the IUCN Red List.

Morphological Characteristics and Systematic Position

Physical Description

The emperor penguin is the largest penguin species, averaging 110–120 cm in height and weighing between 22–45 kg. The upper body is dark black, while the underbody is bright white; characteristic features include broad yellowish-orange patches on the sides of the neck and feathers that fade to pale yellow towards the throat. The head and chin being completely black is among the distinguishing morphological features of the species. There is no obvious sexual dimorphism in adults; males tend to be only slightly larger and heavier than females. The wing bones are densified into powerful, paddle-like flippers; these flippers provide propulsion underwater and also support a balanced stance on land. The feathers are extraordinarily densely arranged and, together with a layer of fat, provide both waterproofing and critical thermal insulation in Antarctic conditions.

Taxonomy and Evolution

Taxonomically, it is most closely related to the king penguin (Aptenodytes patagonicus) within the genus Aptenodytes. Fossil records indicate that the genus originated in the Late Miocene and Early Pliocene (approximately 5–10 million years ago) and that its ancestors evolved by adapting to cold marine environments around Antarctica and the Southern Ocean. Molecular phylogenetic studies reveal that the emperor penguin diverged from the King penguin approximately 1–2 million years ago; this divergence occurred in parallel with the formation of the Antarctic sea ice cover and the expansion of ice-covered coastal regions.

^{Emperor penguin chick (Pexels)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The species forms large colonies on permanent and temporary sea ice along the Antarctic coast; the largest known breeding areas are on Ross Island, Halley, and Pointe Géologie. In colony selection, relatively flat areas with little wind and ice movement, snow and ice thickness, and proximity to chick-feeding routes are key factors. It spends most of its marine life in open waters 50–120 km from the ice edge; most dives occur at depths of 150–250 m, lasting 3–6 minutes, and most foraging activity targets pelagic prey such as fish, krill, and squid.

Feeding Ecology

The majority of its diet consists of fish, particularly Antarctic mesopelagic species such as Antarctic toothfish (Pleuragramma antarcticum) and krill (Euphausia superba); squid and other pelagic invertebrates are important substitute sources when primary prey stocks are depleted. Individuals typically hunt by schooling in the middle and lower parts of the water column, preying on small fish and krill groups. Adults often exhibit synchronised diving in loose schools of 10–50 individuals; this “cooperative hunting pattern” increases hunting efficiency per unit time by compressing prey and directing them towards the surface.

Reproductive Biology

Emperor penguins are monogamous, with pairs returning to the same colony and often the same nest each year. The breeding season begins in the middle of the Antarctic winter; egg-laying usually occurs between May and June. The pair incubates a single egg for approximately 64 days; during this time, the male fasts, enduring the snow and ice while carrying the egg on his feet, as the female goes to sea to feed and later returns. During the first weeks after hatching, the chick is protected by its parents; this is followed by a few weeks of a “nursery” phase, during which the chicks remain in supervised groups. The chicks fledge and enter the sea within 115–130 days; they return to the colony at approximately 4 years of age, having acquired their adult plumage. The moulting period occurs once a year for each individual, during which they remain on land for about three weeks without feeding; sufficient fat reserves are vital during this process.