The Snares penguin (Eudyptes robustus) is an endemic penguin species that breeds only on the Snares Islands, located south of New Zealand. Although its population appears stable, with approximately 25,000 breeding pairs, threats such as the decline in food sources due to climate change, entanglement in fishing nets, oil pollution associated with shipping traffic, and an increase in severe weather events make the species' future fragile. Consequently, it is listed as ‘Vulnerable’ on the IUCN Red List and is protected in New Zealand under the status ‘At Risk – Naturally Uncommon’.

The species' distribution is limited solely to the Snares Islands; therefore, environmental changes or individual events occurring within its habitat have the potential to disproportionately impact the entire population.

Morphological Characteristics and Systematic Position

Physical Description

The snared penguin (Eudyptes robustus) is a medium-sized crested penguin with an average length of 51–61 cm and a mass of 2.8–3.4 kg. The back, head and upper beak are dark blue-black; during moulting/seasonal change, this darkness tends to turn brown. The belly is bright white. The feet and legs are pinkish-white above, and blackish-brown behind the tarsi, on the soles and on the front of the webbing. The yellow crest starts near the nostrils, passes over the eyes and spreads horizontally or hangs slightly behind the eyes. The eyes are reddish-brown in colour. The beak is large and orange-brown in colour; there is a visible patch of bare skin at the base of the beak.

Taxonomy and Evolution

The Snares penguin (Eudyptes robustus) belongs to the genus Eudyptes and is closely related to other ‘crested’ penguins within the genus (such as the Fiordland, rockhopper, and macaroni penguins). The newly discovered fossil species Eudyptes atatu lived approximately 3 million years ago (Pliocene epoch), indicating that the bill structure (deep-billed) of current crested penguins has evolved up to this time; this also indicates that the Eudyptes lineage has undergone adaptations over the last few million years in response to changes in food sources and the ocean ecosystem. Molecular clock analyses suggest that the divergence between the Megadyptes and Eudyptes lineages occurred approximately 15 million years ago, during the Middle Miocene period, while the speciation within Eudyptes spread across the Late Miocene-Pliocene periods.

^{Snares Penguins (Flickr)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The species establishes dense colonies on rocky island chains in the Snares Islands, south of New Zealand, such as North East Island, Broughton Island, and the Western Chain; most colonies are located under scrubby tree cover (e.g., Bird Daisy Olearia lyallii) or dense shrubbery. During the breeding season, males head eastwards from the island towards marine areas during the incubation period; during foraging trips, more productive water bodies such as the Subtropical Front (STF) are 200-300 km away. Females, especially when caring for young chicks, make shorter trips; they typically feed in areas with a radius of 50-100 km, lasting three to seven days. Dive durations and depths vary depending on the temperature and vertical distribution of water masses in the region; while most dives by juveniles feeding occur at depths of 18-30 m and last ~50-80 seconds, dives by males in more distant and colder waters can extend to 120 m.

Nutritional Ecology

The majority of its diet consists of krill (such as Nyctiphanes australis); cephalopods such as small fish and squid are consumed more when krill abundance decreases or during juvenile feeding periods. Individuals hunt in pelagic zones near the coastal shelf rather than the open sea, typically actively foraging in the middle layers of the water column, with dominant behaviour observed in cut-circular or shallow surface fish shoals or coordinated movements with sudden dives. Dive durations are generally short to medium; adults engage in more frequent and shorter dives during the juvenile feeding phase, while those not caring for juveniles may exhibit deeper and relatively longer underwater periods.

Reproductive Biology

The species is monogamous, returning each year to the same breeding colony and often to the same nest; the bond between pairs and their fidelity to the nest increases breeding success each season. The breeding season begins between September and February in the Snares Islands, south of New Zealand; two eggs are usually laid at the end of September, approximately 4-5 days apart. The eggs are incubated by both parents for 31-37 days, and the male parent protects the chicks for the first three weeks after hatching (the ‘guard’ period).

Following this period, the chicks enter the ‘nursery’ stage; that is, several chicks gather in small groups while the parents go out to sea to forage. The chicks are usually ready to fly from the nest (fledging) at around 11 weeks, during which time moulting (transition from down to juvenile feathers) occurs. Adult individuals enter the moulting period after the breeding season in March-April; this process lasts several weeks, and stored fat reserves are critical for survival during this time.

Conservation Status

The species is listed as Vulnerable on the IUCN Red List due to its limited breeding range on the Snares Islands. The extent of occurrence and breeding colonies being confined to a single island group creates vulnerability to arbitrary changes and random threats. The population size is relatively high, at around 25,000 breeding pairs; however, when assessed in conjunction with the risks posed by its restricted distribution, this number is still far from the thresholds that would place the species in the Critically Endangered category. Current data indicate that the population trend is largely stable, with any possible small-scale fluctuations showing no significant decline.^【1】