Blue penguin

Blue penguin, (Eudyptula minor), species of penguin (order Sphenisciformes) characterized by its diminutive stature and pale blue to dark gray plumage. It is the smallest of all known penguin species, and it is the only species of the genus Eudyptula. There are, however, six subspecies: E. minor novaehollandiae inhabits mainland Australia, Tasmania, and southeastern New Zealand, while E. minor minor, E. minor iredelai, E. minor variabilis, E. minor albosignata, and E. minor chathamensis are native to the islands of New Zealand.

Scientists presented evidence for two genetically distinct lineages of the subspecies E. minor novaehollandiae in 2015—one restricted to New Zealand, and another occurring in both Australia and in the Otago Peninsula region of southern New Zealand. Additional studies conducted in 2015 examined feather coloration and vocalization patterns that appeared to differ between the two lineages, which appeared to suggest the possibility of two distinct blue penguin species; however, these studies were inconclusive. In addition, a 2017 study that investigated skeletal dissimilarities between the two lineages noted that the differences between the two were great enough to separate blue penguins into two distinct species. A growing number of researchers have recommended that the Australian lineage be elevated to full species status, as E. novaehollandiae, while the northern New Zealand lineage would remain E. minor. Despite such mounting evidence, such a change remains a matter of debate, since other researchers have cited the need for additional evidence that lays out the morphological, behavioral, and ecological differences between the two groups.

Physical features

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Across all subspecies, adults average about 25–30 cm (about 10–12 inches) in length and weigh between 1 and 1.5 kg (about 2.2 and 3.3 pounds), with males being slightly longer and heavier than females. The color of the plumage covering the top of the head, neck, back, and tops of the flippers ranges from indigo to gray, which contrasts with the white undersides. Juveniles are similar to adults in size, but their feathers are lighter in color. The downy feathers of chicks are colored black and brown.

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Predators and prey

Fish, such as anchovies and pilchards (sardines), are staples of the diet; however, blue penguins also eat squid and crustaceans, including krill. Blue penguins are preyed upon by fur seals (Arctocephalus), killer whales (Orcinus orca), and sharks at sea. On land, blue penguins are also vulnerable to skuas (Catharacta) and introduced predators—such as rats, foxes, dogs, and cats. Eggs and chicks are sometimes claimed from nesting sites by skuas and gulls.

Nesting and breeding

Although the length of the breeding season varies by subspecies and geography, it generally occurs between June and December. Breeding pairs tend to nest in hidden areas that are relatively free of mammalian predators—such as on cliff crevices, in ground burrows, in caves, or under vegetation. Compared with other penguin species, most blue penguins are monogamous; pair breakups are uncommon, occurring only after unsuccessful nesting attempts. Breeding pairs also tend to return to the same nests year after year, and some pairs occupy the same nest year-round.

If mating is successful, a clutch of two eggs is produced. Each parent takes a turn incubating the eggs, while the other returns to sea to feed. This pattern continues after the eggs hatch some 35–37 days later, at which point the parents take turns supplying the chicks with food. The parents also take turns guarding the chicks until the chicks are 18–38 days old. Unlike other penguin species, however, older blue penguin chicks tend to remain in the nest during the day when both parents are out hunting. In general, they do not form “crèches” (groups) with chicks from other nests; however, some studies note that crèches may form among blue penguin chicks that nest in large caves. Fledging, the stage in which the young transition to adulthood, takes place when the chicks are between 50 and 65 days old. During this stage, the young forage in the sea for the first time. Although some may leave the nest during this period, most will remain with their parents before becoming fully independent a few weeks later. Most males and females reach sexual maturity at age three. While the life span of the blue penguin is generally six to seven years, some studies note that a few individuals can live as long as 25 years in the wild.

Conservation status

Since 1988 the blue penguin has been listed as a species of least concern on the International Union for Conservation of Nature’s Red List of Threatened Species. Ecologists base this classification on the species’s high numbers and extremely large geographic range. Although a definitive population count has not been performed, several studies estimate the population at more than one million blue penguins worldwide, with the majority located in Australia. On the other hand, the population of some colonies has declined from the effects of introduced predators, increased competition with commercial fishing for food resources, and habitat fragmentation brought about by building and road construction.

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