Gentoo penguin

Name and taxonomy

The scientific name of the gentoo penguin is Pygoscelis papua. Pygoscelis means rump-tailed. The name fits the way the long tail sweeps from side to side as the bird walks. Johann Reinhold Forster gave the first description in 1781. He set the type locality in the Falkland Islands.

The species name is an error. Forster believed the bird lived in Papua, and no penguin has ever lived in New Guinea. The nearest gentoos are over 6,000 km to the south, on Macquarie Island. Some writers blame a doubtful claim made in 1776 by the French naturalist Pierre Sonnerat. He put the king penguin in the same place, and he had never been there.

The English word gentoo is also unclear. It was an Anglo-Indian term that marked out Hindus from Muslims. It may come from the Portuguese gentio, and the white head patch may have suggested a turban. Another idea traces it to Johnny penguin, an old sailors' name for the bird. The Johnny rook, a bird of prey that hunts near the colonies, probably took its name from that.

Evolution and relatives

Three species make up the genus Pygoscelis, and the gentoo is one of them. The other two are the Adelie penguin and the chinstrap penguin. DNA puts the split of the genus from other penguins at about 38 million years ago. That is roughly 2 million years after the line that led to the emperor and king penguins. The Adelie parted from the rest about 19 million years ago. The chinstrap and the gentoo separated about 14 million years ago.

Taxonomists once recognised only two subspecies. A study in 2020 argued that the gentoo is four separate species that look much alike. The proposed names cover northern, southern, eastern and South Georgia birds. The International Ornithological Congress took the results in 2021 but kept them as subspecies. A 2026 study of ten colonies again proposed four species, and it added the Kerguelen birds. The question is probably not settled yet.

Appearance

An adult measures 70 to 90 cm long and weighs 4.5 to 8.5 kg. Weight swings hard through the year. A male peaks near 8.5 kg just before the moult and drops to about 4.9 kg before mating. A female peaks at 8.2 kg and can fall to 4.5 kg while she guards the chicks. Northern birds average 700 g heavier and 10 cm longer than southern ones.

The head is black with two white wedges around the eyes, joined by a band over the crown. The bill is orange-red, and the colour comes from carotenoid pigments in the krill. The webbed feet are pale and carry long black claws. The tail holds 14 to 18 feathers and runs about 15 cm long. No other penguin has a tail that long, and the group is called the brush-tailed penguins.

The back is black and the front is white, a pattern known as countershading. The feathers are very fine, and a square inch of skin can carry up to 70 of them. Oil from a gland near the tail keeps the plumage waterproof. Males are larger than females in bill length, flipper length and height. A chick keeps grey down until its first moult at about 14 months.

Habitat and range

The gentoo penguin lives only in the Southern Hemisphere, between 45 and 65 degrees south. Only about 13% of the world total lives south of the Antarctic pack ice. The Falkland Islands hold around 40% of all gentoos. Other main colonies sit on South Georgia, the South Sandwich Islands and Kerguelen. Smaller groups breed on Macquarie, Heard, the Crozet Islands, the South Shetlands and the Antarctic Peninsula.

Colonies always sit on ice-free ground. Some are right on the shore and some are well inland, up to 2 km on South Georgia. Birds pick flat ground near 115 metres above the sea, where the snow melts first. A high, flat site is less likely to flood when the melt starts. North-facing slopes are preferred, which is thought to be about catching the sun.

The one thing every colony needs is small pebbles, usually under 5 centimetres across. Inland colonies nest between tufts of grass. Those colonies shift a little each year, because the birds trample the grass flat. The species is recorded in 20 countries on GBIF.

Diet and feeding

Gentoo penguins live on fish, crustaceans and cephalopods. The mixture changes sharply through the year. In February and March crustaceans supply about 10% of what a gentoo eats. From March to June that share rises to about 75%. From June to October grey rockcod supply 90% of what the birds eat. Cephalopods stay near 10% all year round.

Around the Falklands the birds take fish, squat lobsters and squid in roughly equal shares. They are opportunists and switch to whatever is close and plentiful. Most feeding happens in shallow water near the colony. A typical dive reaches only 3 to 20 metres, though some go to 70 metres. The longest recorded dive lasted two minutes. Metabolism slows under water, which stretches the time a bird can stay down.

The gentoo is the fastest underwater swimmer of all penguins, at up to 36 km/h. Seawater comes in with the food, so the diet is very salty. A gland above the eyes strips the salt out and drips brine from the bill tip. Parents bring food back and bring it up again for the chicks.

Behaviour and social life

Gentoo penguins breed in colonies that can hold over 2,000 pairs. Nests sit about a metre apart. A bird defends only the square metre around its own nest. Stones are the currency of the colony, and birds guard and steal them. A male can win a female by offering her a good stone.

A neighbour that comes too close gets a jab of the bill and a low hiss. Two birds may lock bills and try to twist each other away. Fights with bill and flipper happen, but they are rare.

Most gentoos stay near the breeding ground all year. They move only when ice closes the site. From January the adults make long feeding trips and put on weight fast. That period runs about 55 days and prepares them for the moult. The moult itself takes 25 days, during which the bird cannot swim and must fast. A moulting gentoo loses about 200 grams a day.

Communication and senses

The best known call is a loud trumpet, given with the head thrown back. Males call at a higher pitch and at greater volume than females. A bird returning from the sea points its bill up and squawks to announce itself. The mate on the eggs answers with a loud display or with a bow and a low hiss. The changeover on the nest usually takes about three minutes.

A mild threat draws a low hiss and a closer one draws grunts. Chicks beg with high chirps and use a whistle call until their first moult. A chick can pick out its own parents among thousands of calling adults. Bill rubbing and face rubbing appear to strengthen the bond between a pair.

Sight appears to be the leading sense in the water. The retina is most sensitive to green, blue and violet, the colours that reach depth. The same eye works poorly once the bird comes ashore.

Reproduction and life cycle

A male picks a flat patch with little snow and stands over it. He points his bill straight up and calls to bring females in. A female who approves joins him in trumpeting or bowing. Pairs stay together for the season, and some bonds last for life. The divorce rate is under 20 percent, which is low for a penguin. A female that changes mate usually picks one with a better breeding record.

Both birds build the nest, a shallow bowl of stones. It stands 10 to 20 cm high and measures about 45 cm across. A medium nest can hold over 1,700 pebbles, some of them stolen. Laying starts between June and mid-August and ends between late October and late November. The female lays two greenish-white eggs three days apart. Each egg weighs around 130 g.

Both parents incubate and swap duty every day. The eggs hatch after 34 to 36 days, usually together or a day apart. A newly hatched chick weighs about 96 grams and is very weak. Parents guard it in the nest for about 30 days. The chicks then gather with others in a crèche while both parents fish.

Young birds moult into subadult plumage and go to sea at 80 to 100 days. They reach independence between 85 and 105 days. A gentoo can breed at two years old, but most wait until three or four. If a clutch is lost, the female can lay again later in the same season. A wild bird lives about 13 years on average. The oldest bird on record, a zoo penguin called Olde, reached 41 years.

Predators and threats

No land animal takes a healthy adult gentoo. The danger is in the water. Leopard seals wait off the colony and catch birds as they come and go. They take most chicks in the days when the young first enter the sea. Sea lions, Weddell seals, fur seals and orcas all take gentoos as well.

Brown skuas are the main killers of eggs and chicks on land. They work the edge of the colony, where a chick stands alone. A crèche makes it hard to pick out one bird, so it works as a defence. Giant petrels kill chicks and finish off sick adults. Kelp gulls and snowy sheathbills also snatch eggs and young. Skuas on King George Island have injured adult gentoos in territorial disputes.

Crowded colonies carry heavy loads of fleas and ticks. The tick Ixodes uriae attacks bare skin on the feet, face and ear canals of chicks. Several tapeworms live in the gut and arrive with the crustaceans the birds eat.

Population and conservation

The IUCN listed the gentoo as Least Concern in 2019, with a stable trend. Animal Diversity Web gives a world total of about 628,000 birds. The Australian Antarctic Program counts roughly 387,000 breeding pairs. No other penguin of the sub-Antarctic islands has a smaller total than that.

Numbers are rising quickly in the maritime Antarctic. As the region warms, the birds settle ground further south that they could not use before. Some long-held sites are falling fast at the same time. On Bird Island, South Georgia, the colony lost two thirds of its birds over 25 years.

Pollution, fishing, hunting and visitor traffic all press on the species. Protected areas cover breeding ground on Macquarie Island and Heard Island. Longer monitoring of the colonies is the measure most often proposed. iNaturalist holds 5,588 observations of the species.

Relationship with humans

Sealers once boiled penguins down for oil to burn. Hundreds of thousands died, and some colonies never recovered. People also used gentoo skins for caps, clothes, slippers and purses. Sailors and islanders gathered the eggs in quantity into the late 1980s.

None of that trade appears to continue today. Farm animals have trampled nests on some islands. Tourism probably brings more people to the colonies now than any other activity. That traffic counts as one of the pressures on the species. The gentoo does no harm to people at all.

In culture and myth

The gentoo appears to carry two old confusions in its name. One placed the bird in New Guinea and the other borrowed a word from British India. Falkland sailors called it the Johnny penguin, and a local falcon became the Johnny rook.

The bird gave its name to Gentoo Linux. Daniel Robbins first called that project Enoch Linux and then renamed it. He picked the bird for its speed in the water, which no other penguin matches. The system builds its software from source and tunes it to each machine for speed. A penguin is also the general mascot of Linux.

Six gentoos appeared in the 2011 film of Mr. Popper's Penguins. The script named them Captain, Lovey, Loudy, Bitey, Stinky and Nimrod. The species is probably the penguin most visitors to the Falklands meet.