The application of gentoo to the penguin is unclear. Gentoo was an Anglo-Indian term to distinguish Hindus from Muslims. The English term may have originated from the Portuguese gentio. Some speculate that the white patch on the bird's head was thought to resemble a turban. It may also be a variation of another name for this bird, "Johnny penguin", Johnny being Juanito in Spanish and sounds vaguely like gentoo. The Johnny rook, a predator, is likely named after the Johnny penguin. The specific namepapua is a misnomer; in the original description, Johann Reinhold Forster, a naturalist who had circumnavigated the world with Captain James Cook, mistakenly assumed that the species occurred in Papua, the closest gentoos actually being over 6000 km to the south. There are no penguins in New Guinea. Others trace the error to a "possibly fraudulent claim" in 1776 by French naturalist Pierre Sonnerat, who also alleged a Papuan location for the king penguin despite never having been to the island himself.
Taxonomy
The gentoo penguin is one of three species in the genus Pygoscelis. Mitochondrial and nuclearDNA evidence suggests the genus split from other penguins around 38 million years ago, about 2 million years after the ancestors of the genus Aptenodytes. In turn, the Adelie penguins split off from the other members of the genus around 19 million years ago, and the chinstrap and gentoo finally diverged around 14 million years ago. Two subspecies of this penguin are recognised: Pygoscelis papua papua and the smaller Pygoscelis papua ellsworthi.
Description
The gentoo penguin is easily recognized by the wide white stripe extending like a bonnet across the top of its head and its bright orange-red bill. It has pale whitish-pink webbed feet and a fairly long tail – the most prominent tail of all penguin species. Chicks have grey backs with white fronts. As the gentoo penguin waddles along on land, its tail sticks out behind, sweeping from side to side, hence the scientific name Pygoscelis, which means "rump-tailed". Gentoos reach a height of, making them the third-largest species of penguin after the emperor penguin and the king penguin. Males have a maximum weight of about just before molting, and a minimum weight of about just before mating. For females, the maximum weight is just before molting, but their weight drops to as little as when guarding the chicks in the nest. Birds from the north are on average heavier and taller than the southern birds. Southern gentoo penguins reach in length. They are the fastest underwater swimmers of all penguins, reaching speeds of up to. Gentoos are well adapted to extremely cold and harsh climates.
Breeding
The breeding colonies of gentoo penguins are located on ice-free surfaces. Colonies can be directly on the shoreline or can be located considerably inland. They prefer shallow coastal areas and often nest between tufts of grass. In South Georgia, for example, breeding colonies are 2 km inland. In colonies farther inland, where the penguins nest in grassy areas, they shift location slightly every year because the grass will become trampled over time. Gentoos breed on many sub-Antarctic islands. The main colonies are on the Falkland Islands, South Georgia and the South Sandwich Islands, and Kerguelen Islands; smaller colonies are found on Macquarie Island, Heard Islands, Crozet Islands, South Shetland Islands, and the Antarctic Peninsula. The total breeding population is estimated to be over 600,000 birds. Gentoos breed monogamously, and infidelity is typically punished with banishment from the colony. Nests are usually made from a roughly circular pile of stones and can be quite large, high and in diameter. The stones are jealously guarded and their ownership can be the subject of noisy disputes and physical attacks between individuals. They are also prized by the females, even to the point that a male penguin can obtain the favors of a female by offering her a choice stone. Two eggs are laid, both weighing around. The parents share incubation, changing duty daily. The eggs hatch after 34 to 36 days. The chicks remain in the nests for around 30 days before joining other chicks in the colony and forming crèches. The chicks molt into subadult plumage and go out to sea at around 80 to 100 days.
Diet
Gentoos live mainly on crustaceans, such as krill, with fish making up only about 15% of the diet. They are, however, opportunistic feeders, and around the Falklands are known to take roughly equal proportions of fish, squat lobsters, and squid.
Physiology
The gentoos' diet is high in salt as they eat organisms with relatively the same salinity as sea water, and this can lead to complications associated with high sodium concentrations in the body, especially for gentoo chicks. To counteract this, gentoos as well as many other marine bird species have a highly developed salt gland located above their eyes that takes the high concentration of sodium within the body and produces a highly saline-concentrated solution that drips out of the body from the tip of the beak. Gentoo penguins do not store as much fat as the Adelie penguin, their closest relative: gentoos require less energy investment when hunting because the net gain of energy after hunting is greater in gentoos than Adelies. As embryos, gentoos require a lot of energy in order to develop. Oxygen consumption is high for a developing gentoo embryo. As the embryo grows and requires more oxygen, the amount of consumption increases exponentially until the gentoo chick hatches. By then, the chick is consuming around 1800 mL O2 per day.
Predators
In the sea, leopard seals, sea lions, and killer whales are all predators of the gentoo. On land, no predators of full-grown healthy gentoo penguins exist. Skuas and giant petrels regularly kill many chicks and steal eggs; Petrels will kill injured and sick adult gentoos. Various other seabirds, such as the kelp gull and snowy sheathbill, will also snatch chicks and eggs. Skuas on King George Island have been observed attacking and injuring adult gentoo penguins in apparent territorial disputes.
Conservation status
, the IUCN Red List lists the gentoo as least concern, although rapid declines in some key areas are believed to be driving a moderate overall decline in the species population. Examples include Bird Island, South Georgia, where the population has fallen by two-thirds over 25 years.
Influence
The Linux distribution Gentoo Linux is named after the Gentoo penguin. This is a nod to the fact that the penguin is the fastest swimming penguin, as Gentoo Linux aims to be a high performance operating system.
