The chinstrap penguin (Pygoscelis antarcticus) is a species that breeds in colonies spread across the Southern Ocean, primarily on the Antarctic Peninsula and neighbouring islands. Its most distinctive feature is the thin black line that runs across the lower part of its head. With a global population exceeding 8 million, this species is a member of the ‘Pygoscelis trio’ along with the Adélie and Gentoo penguins. Its diet consists mainly of Antarctic krill (Euphausia superba); therefore, its population dynamics are closely linked to krill abundance and distribution. Since the 1980s, local declines have been recorded in some areas due to climate change, reduced sea ice, and pressure on krill stocks from commercial fishing. However, as the species still forms large and widespread colonies globally, it is classified as ‘Least Concern’ (LC) on the IUCN Red List.

Morphological Characteristics and Systematic Position

Physical Description

The chinstrap penguin is a medium-sized penguin, measuring 68–76 cm in length and weighing 3.5–5 kg. The back of the body is dark black, while the belly and throat are white; a thin black feather stripe running from one side of the head to the other, just below each reddish eye and joining under the beak, allows for individual identification. Male and female chinstrap penguins are monomorphic (identical in appearance); it is difficult to distinguish them without non-morphological clues. The wing bones have thickened into strong flippers that provide propulsion during swimming; the feathers are densely arranged and coated with oil, providing both waterproofing and thermal insulation.

Taxonomy and Evolution

Taxonomically, within the genus Pygoscelis, they are close relatives of the Adélie and Gentoo penguins. The southernmost parts where Chinstrap Penguins live, the South Sandwich Islands, South Orkney Island, South Shetland Islands, and the western Antarctic Peninsula up to 64°S, overlap with the northernmost parts of the Adélie Penguins. Where the species overlap, colonies are usually entirely of a single species or have species-specific clusters within larger colonies. In larger, mixed colonies, it is rare for more than two penguin species to breed.

The taxonomic history of the Palaeeudyptes genus is complex. Antarctic material assigned to this genus has been divided into two species: P. klekowskii and P. gunnari. The New Zealand record for Palaeeudyptes is more complex. The holotype specimen of Palaeeudyptes antarcticus is a tarsometatarsus with a large portion of metatarsal II missing. Names such as Marples (1952), Brodkorb (1963), and Simpson (1971) assigned numerous specimens to this taxon in their examination of New Zealand fossils. A combined (DNA + morphology) analysis yielded a tree consisting of 4308 steps. The topology of the fossil taxa (excluding the fossil species of Spheniscus) is identical to that obtained from the morphological analysis. All extant genera are monophyletic in the robust consensus tree of the combined analysis. All analyses supported a similar phylogenetic hypothesis and placed Aptenodytes as the sister clade to all other extant penguin species. It differs from other clades containing the genera Pygoscelis, Spheniscus + Eudyptula, and Megadyptes + Eudyptes.

Reconstructions of ancestral distributions identified the coastal regions of Australia, New Zealand, and nearby islands as the most likely habitat of the ancestor of extant penguins. The genus Aptenodytes (king penguins) was established in Antarctica, and the reconstructed ancestral Pygoscelis species (chinstrap, Adélie, and gentoo) colonised the Antarctic Peninsula shortly after Aptenodytes.

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Ecology, Behaviour and Life Cycle

Habitat and Distribution

The chinstrap penguin forms colonies in areas stretching from the northern coasts of the Antarctic Peninsula to the South Orkney and South Shetland Islands. Colony selection is largely dependent on ice-free, dry, and steeply sloping areas. They spend most of their marine life in waters close to colonies, typically feeding within a few dozen kilometres of the coast. Most dives occur at depths of 10–40 metres and last 30–60 seconds, though they can occasionally dive to depths of up to 70 metres.

Feeding Ecology

Over 90% of their diet consists of Antarctic krill (Euphausia superba); fish and small cephalopods are secondary and seasonal prey. Individuals typically target krill swarms in the middle of the water column, circling around dense swarms to exert feeding pressure. Adults, particularly during the breeding season, perform synchronised dives in loose groups that can number in the hundreds; this “cooperative shoaling strategy” increases energy efficiency by compressing krill swarms and making them more accessible.

Reproductive Biology

Chinstrap penguins are monogamous, and pairs typically return to the same nesting area each year. The breeding season mostly occurs between November and March; two eggs are laid in simple nests made of stones and gravel within colonies. Partners take turns incubating the eggs, and the chicks hatch after approximately 37 days. For the first 3–4 weeks after hatching, the chicks are protected in the nest by one of the parents, then enter a communal rearing phase known as a crèche. The chicks leave the nest after 50–60 days and head for the sea; after spending their early years roaming the open ocean, they return to breeding colonies once they have acquired their adult plumage. During the annual moulting period, they remain on land without feeding for several weeks; during this time, their previously stored fat reserves are vital for survival.

Conservation Status

The chinstrap penguin (Pygoscelis antarcticus) was last assessed on the IUCN Red List of Threatened Species in 2020. This assessment noted that the species has a fairly wide distribution range and therefore does not approach the thresholds for the Vulnerable category in terms of distribution size. It was also emphasised that the population trend is increasing and therefore does not reach the Vulnerable level in terms of the population trend criterion. Due to the high population size, it was stated that the species does not fall into any threat category in terms of the population size criterion. For these reasons, the species is classified as Least Concern.