Gentoo penguin
Gentoo penguin on shingle beach, Ardley Island, Antarctica. @ C.Michael Hogan
The Gentoo penguin (scientific name: Pygoscelis papua) is one of seventeen species of flightless birds in the family of penguins. It is one of three "Brush-tailed penguins" in the genus 'Pygoscelis, which also includes the Adelie and the Chinstrap penguins.
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Conservation Status  |
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Scientific Classification Kingdom: Animalia |
The Gentoo penguin is characterized by its erect posture, triangular white patches above the eyes, bright orange-red bill, and bold black and white colouration patterning. P.papua is the swiftest swimmer of all penguin species, with a broad circumpolar distribution within the Southern Ocean . A common ancestor to all species within the genus Pygoscelisis dated to approximately 20 million years before present.
Contents
Description
Gentoo penguins have black heads and distinct triangular white patches above each eye usually extending over the head. They have a body mass ranging between 5.0 and 6.2 kilograms (kg). They stand from 51 to 71 cm tall and have a relatively long tail. Juveniles have smaller, less distinct white patches and sometimes a gray throat. Males and females are similar in size and appearance.
Two sub-species have been recognized, Pygoscelis papua ellsworthi and Pygoscelis papua papua. P.p. ellsworthi penguins are smaller in size, with longer feathers, a shorter bill, smaller feet and smaller wings.
Behavior
Throughout the year adults can be found on breeding islands indicating that they are relatively sedentary. They exhibit a strong diurnal pattern in their diving behavior. Deep diving begins near sunrise and finishes at sunset. Diving at night is less common and is often shallow. Dive time duration of up to seven minutes have been recorded. Dive depths range from 40 to 210 meters (m).
Individuals swim at 1.04 meters per second and have a maximum potential foraging range of about 26 kilometers (km) for single day trips. They tend to forage within 14 km of the colony with a mean range of 5.4 km.
Reproduction
Males display to establish a nest site and attract a mate. Females choose a male and his territory. Nests are made of circular piles of stones, tussock grass, or moss. Females fast for five days before egg laying. A clutch of two eggs is produced with an interval of three to four days between them. The incubation period is about 36 days.
The first egg laid is larger than the second one and usually hatches first. Egg weight varies with age of breeding and nest location. Young first time breeders typically lay smaller eggs and have lower breeding success compared to older experienced birds. The breeding season is from spring to autumn. Sexual maturity is normally attained at the age of six years. Gentoo are the least abundant of penguin species with a total breeding population of approximately 314,000 pairs.
Distribution
Gentoo colony on Ardley Island, Antarctica. Source: C.Michael Hogan
Gentoo penguins are distributed in a broad circumpolar manner in the Southern Ocean, especially the Bellingshausen Sea and Amundsen Sea. Breeding areas include temperate and Antarctic islands to a latitude of 65 degrees south on the Antarctic Peninsula. Specific breeding locations include coastal areasof the Falkland Islands (United Kingdom), South Georgia, Kerguelen Islands (France), Crozet Islands (France), Heard Island (Australia), MacQuarie Island (Australia), McDonald Islands (Australia), South Sandwich Islands, South Shetland Islands, South Orkney Islands, Marion Island (South Africa), Prince Edward Island (South Africa), Martillo Island (Argentina) and the Antarctic Peninsula. Some non-breeding sightings have been reported as far north as waters of New Zealand, although these observations are not fully authenticated.
Habitat
This species is terrestrially typically found on bare hillsides and beaches close to their breeding colonies, and thus their chicks can be fed frequently. Breeding colonies may often occur on shingle beaches, where the availability of small stones and pebbles afford good opportunistic nest arrangement substrates.
Prey and predators
Gentoo Penguins take both small plankton and large prey, especially squid and fish. In Antarctic regions approximately 85 percent of the caloric intake is from small crustaceans or krill, whereas sub-Antarctic feeding is dominated by fish as well as large invertebrates. Dominant fish prey taxa are of the genus Gymnoseopelus and Paranotothenia magellanica. Both pelagic and benthic prey are eaten but benthic species comprise a larger proportion of the diet. In the Falklands, a higher dietary content of large prey is evinced, notably Patagonotothen sp., Thysanopsetta naresi, Micromesistius australis, crustaceans (Munida gregaria) and squid (Loligo gahi, Gonatus antarcticus, Moroteuthis ingens).Females tend to eat more krill than males. Males tend to eat more fish than the females. The Gentoo is capable of securing larger prey than that taken by other penguin species as a consequence of the large size and elongated bill of the Gentoo. Chief marine predators are the Leopard seal, Orca and some seal lion and fur seal species from the family Otariidae. There are no natural terrestrial mammalian predators, although some human natives of the Falklands are known to have historically harvested Gentoo eggs. Major avian predators are Brown Skuas, which prey on eggs and chicks, and Sheathbill, Caracaras and Dominian gulls which prey on eggs. Other terrestrial predators include kelp gulls and feral cats. It has been estimated that total annual energy budget of a 6.2 kg breeding Gentoo Penguin is 1517 megajoules, which is equivalent to the consumption of 292 kg of prey.
Evolution
A common ancestor of all penguin and albatross species has been postulated to have existed in Gondwana approximately 71 million years ago (Mya), when Australia, Antarctica and South America were attached. (Baker et al. 2006) Common ancestry to all extant penguin genera was deduced to have existed at approximately 39 to 41 Mya. These timelines were established by DNA molecular sequencing studies, but are also supported by fossil evidence. Appearance of the genus Pygoscelis occurred considerably before present, with breeding colonies at least as early as the Pleistocene in the far north as New Zealand, due to the warmer weather of that era. The species within the genus have evolved during several climate oscillations involving glacial advance and retreat, leading to species adaptability to climate change. A common ancestor to all the penguin species is suggested as late as 40 Mya, when genus Aptenodytes diverged as the basal lineage; moreover, while the common ancestor for genus Pygoscelis is evidenced at 20 Mya based upon genomic sequencing; furthermore, the Chinstrap and Gentoo, which are closely related within the genus, have a suggested common ancestor at around 15 Mya.
Conservation status
According to the IUCN Red List, Gentoo penguins are Near Threatened. Approximately one fourth of the extant population is within the Antarctic Peninsula, with the remainder at sub-Antarctic islands. There were an estimated minimum 317,000 breeding pairs as of 2007, chiefly occurring in the Falkland Islands, South Sandwich Islands, South Shetland Islands, Macquarie Island, Heard Island, Kerguelen Islands and South Georgia, with the Falkland and South Georgia populations each estimated at around 115,000 breeding pairs; however this estimate may exceed actual current population numbers, due to the recent declining trend for the species. Gentoo population declines have been widely documented over the last few decades. For example the Bird Island, South Georgia population diminished by twenty percent between 1985 and 2005. South Georgia observations noted that scarcity of krill was strongly correlated with decrease in breeding success, with breeding rates falling by ninety percent in the worst years.
On Marion Island the Gentoo population declined by approximately forty percent between 1994 and 2005, attributed again to food shortage. Dramatic declines in the Falkland colonies occurred in the period 2002 to 2003; it has been suggested that ocean algal blooms were responsible for this unusual mortality, since large numbers of Gentoos arrived on the beaches partially paralysed, and swiftly succumbed; in addition, this was the same period where massive losses in Patagonian fisheries occurred, which deaths were traced to red tide or algal blooms. Furthermore, the behavior pattern noted in the Gentoo deaths is identical to the neurological toxicity known to be associated with red tides.
To balance the dialog, it should be noted that Gentoo populations have the capability of rapid rebuilding. The 2007 population is not dissimilar to the mid 1980s, although intermediate declines of as much as one third were observed within that span of time. Historically colonies have been affected by egg collecting and capture of adults for extraction of oil. Historic exploitation is particularly noted in the Falkland Islands and South Georgia. Specific Gentoo population declines on Marion Island between 1975 and 1985 have been attributed to the presence of feral cats, although that hypothesis has not been clearly proven The Antarctic Treaty was signed in 1959 by twelve nations. Among other things, the treaty made it illegal to harm Gentoo penguin species or their eggs. Every individual Gentoo collected with a permit must be approved by and reported to the Scientific Committee for Antarctic Research. Nevertheless, sub-Antarctic populations have recently been decreasing at a significant rate. Protection of habitat began in early 1900's. In 1924 the French declared the Kerguelen Islands off the coast of Antartica a national park. Gentoo species include marine pollution and overfishing practices which harvest considerable amounts of species fundamental to the Gentoo diet.
Economic Importance for Humans
Gentoo penguin skin has been exploited to produce clothing and accessories such as caps, slippers and purses. The feathers have been used for clothing and decorations. Their fat layer has also been exploited to extract oil. In earlier times rural human populations in the Falklands harvested Gentoo eggs as a source of dietary protein; these practices have currently subsided to a great extent. The total economic value of the species is far greater than any imputed current economic benefit; in addressing the total economic benefit one considers the existence benefit (value placed on the species for observation and for willingness to preserve the species) as well as the legacy benefit, or that value for future generations in supplying enjoyment as well as genetic resources which can prove valuable in scientific research and pharmaceutical sources.
References
- Pygoscelis papua (J. R. Forster, 1781) Encyclopedia of Life (accessed March 11, 2009)
- Species 2000 & ITIS Catalogue of Life: 2009 Annual Checklist. Bisby FA, Roskov YR, Orrell TM, Nicolson D, Paglinawan LE, Bailly N, Kirk PM, Bourgoin T, Baillargeon G., eds (2009), Species 2000: Reading, UK.
- ARKive
- Animal Diversity Web, University of Michigan Museum of Diversity
- WoRMS, World Registry of Marine Species
- International Union for the Conservation of Nature: Pygoscelis papua IUCN Red List] (September, 2007)
- BirdLife International (April, 2003)
- Global Register of Migratory Species (March, 2008)
- International Penguin Conservation (April, 2003)
- Animal Diversity Web (April, 2003)
- E.M.van Zinderen Bakker Jr. 1971. A behaviour analysis of the gentoo penguin. In Marion and Prince Edward Islands, edited by E.M.van Zinderen Bakker Jr.
- G.A.Knox. 2007. Biology of the Southern Ocean
- CRC Press. 621 pages *Ian Strange. 1972. The Falkland Islands
- David and Charles Publishers. 236 pages
- L.Davis and J.Darby. 1990. Penguin Biology. Academic Press, San Diego, California
- Dietland Müller-Schwarze. 1984. The behavior of penguins: adapted to ice and tropics. SUNY Press. 193 pages
- David G.Ainley. 2002. The Adelie penguin: Bellweather of climate change. Columbia University Press.
