, or more commonly known as gentoo penguins, are exclusively found in the Southern Hemisphere between 45 and 65 degrees south latitude. Within this range, gentoos are found on the Antarctic Peninsula as well as many sub-Antarctic islands. Only about 13% of all gentoo penguins live south of the Antarctic ice pack.
Gentoo penguins typically are found along the shoreline. This allows the penguins to be able to quickly access food while remaining close to their nest. They prefer elevations close to 115 meters above sea level along the shore because the snow in these areas tends to melt first. The higher the altitude, the decreased likelihood of nest-flooding as the snow starts to melt during the summer. The terrain in these areas is also flat which helps to stabilize their nests. Gentoo penguins prefer north-facing locations for nesting, which is thought to be linked to absorbing solar radiation. The main feature of gentoo habitats is the prevalence of small pebbles, typically under 5 centimeters in diameter. These pebbles are the main building blocks in creating a sufficient nest to hold the eggs during breeding season.
Gentoo penguins also spend some of their day underwater for feeding excursions. These aquatic trips are typically short; the longest dive on record is only two minutes long. Gentoos typically dive down only 3 to 20 meters, with occasional deeper dives up to 70 meters. (Adams and Brown, 1983; Quintana, 2001)
Like all penguin species, the ventral side of gentoo penguins is white while the dorsal side is black. This color pattern is known as countershading. This adaptation is useful while swimming underwater; the lightly colored ventral side helps penguins blend in with the sky for predators or prey that are looking up. The dark dorsal side blends in with the ocean floor for predators or prey looking down.
The major difference between gentoo penguins and other penguin species are their head markings. Gentoos feature two white wedges around their eyes that are connected by a medium-sized line across the tops of their heads. Their heads are mostly covered in black feathers but small flecks of white feathers can also be found.
The feathers of gentoos are very fine; every square inch of their body can be covered with up to 70 feathers. Gentoos are part of a group called the "brush-tail penguins" which characterizes their tails as having longer feathers than those of other penguin species. Their tails consist of 14 to 18 feathers and are about 15 centimeters long. Because gentoos are aquatic, they must make their feathers waterproof. Using their bills, they do so by covering their feathers with oil found in the uropygial gland near the base of their tails.
Of the 17 penguin species, gentoo penguins are the third largest in size. They stand roughly at 76 centimeters when they reach adulthood. Depending on the time of the year, they can weigh anywhere from 4.5 to 8.5 kilograms. Heavier weights are seen during their month-long molting phase.
Their feet are stout, fat, and webbed. They are bright orange with long black claws extending from the webbing. The beak of a gentoo is partially black but has a bright dark-orange to red spot on either side. The color of the spot is attributed to the carotenoids absorbed from the krill they eat.
There is very little difference between the males and females. The main characteristic differentiating between the sexes is size. Males are significantly larger than females in almost all respects such as bill length, flipper length, and height.
Gentoo penguins look very similar from the time they hatch until their first molt which occurs at around 14 months. Chicks have downy-gray feathers and a weak, dull-colored bill. The white wedges around the eyes are noticeable at a young age; however, they are not as well-defined or connected along the top of their head like the adults. (Cuervo, et al., 2009; McMillan, 1993; Naveen, 1999; Renner, et al., 1998; Williams, 1995)
Females' choice of male mates is based on male behaviors. First, the male gentoos find the best spot for a potential nest. The prime areas are those that are flat with little to no snow or ice. Once a potential nest site is chosen, the males point their bills vertically in the air and bellow out calls. The calls announce to the females to come and investigate their nest site. If a female waddles by and "likes" the nest site, the male and female will mutually display by trumpeting or bowing.
Gentoo penguins are monogamous during a breeding season, with some pair bonds lasting a lifetime. "Divorces" (the breaking of pair-bonds) do occur between breeding seasons. In this case, females choose a new partner that has displayed greater reproductive success. As colonial breeders, direct observation of nesting success is possible. The divorce rate in gentoos is less than 20 percent, which is relatively low compared to other penguin species. The benefit to a monogamous relationship is that mates do not have to expend time and energy finding new mates each year. (Croxall and Davis, 1999; Frédérique, et al., 1998; Williams, 1995)
Gentoo penguins can begin breeding at two years of age, although most don't until they are about three or four. Living in colonies, gentoo penguins can gather in groups of over 2,000 pairs at one breeding site. At the beginning of the breeding season, nests are built by the parents. Gentoo nests are spaced about a meter apart. The egg-laying season for P. papau begins from June to mid-August and usually finishes in late October to late November.
After the nest has been completed, the female will stay at the nest and lay her egg 5 days post-breeding. A second egg is laid three days later. The eggs are spherical and greenish-white. The weight of the first egg in relation to the second egg varies between nesting locations, but on average egg weight is 125 grams. There have been rare cases where one or three eggs were laid.
If the set of eggs is lost, gentoo penguins can lay a second set of eggs during the same breeding season. These eggs are laid near the end of the breeding season when the female regains sufficient energy. The downside to a late laying is reduced energy, causing a late molting period. Females do not have enough energy to begin their molt right after breeding and therefore delay molting. This, in turn, delays egg-laying the following year. Indeed, the female may not have enough energy to lay a clutch the next year.
The eggs are incubated for an average of 35 days before hatching. Although the eggs are laid days apart from each other, they typically hatch on the same day or one day apart. The chicks are frail and weigh about 96 grams. The chicks stay at the nest for the first 75 days until they are ready to fledge and visit the ocean for the first time. During this fledging period, gentoo chicks make an average of 5 trips to sea. The young reach independence 20 days post-fledging. (Bost and Jouventin, 1990; McMillan, 1993; Williams, 1995)
Both parents are involved in nest-building. The nest is bowl shaped with a wide edge and a hollow center. Nest size ranges between 10 to 20 cm in height and around 45 cm in diameter. Nests are made from small stones found around the nesting site, including stones stolen from other nests. Medium-sized nests can contain over 1,700 pebbles. Although pebbles are the main component of nests, sometimes molted feathers, twigs, and vegetation are used.
Members of both sexes defend their nests from other birds that come too close. P. papau will stick out its bill toward the invader and let out a low hiss. Competition for territory exists between two adjacent nests in which parents will turn their neck towards their neighbor and try to grab and twist their bill. Although rare, fighting with bills and flippers has been observed.
The female lays two eggs within 3 days of each other. The eggs are kept safely under the male or female for the 35 days of incubation. For the first three to four weeks, the chicks are guarded in the nest. The parents take turns getting food and regurgitating it for the chicks. Near the end of this stage, the chicks begin to move short distances away from the nest and form groups with other chicks (creches). These groups serve to protect against predators while both parents to forage for the growing young. The young fledge at 70 days old and will enter the sea for the first time. Both parents will still feed their chicks (although not as often) during the fledging period. Feedings have occasionally been recorded post-independence. (Gales, et al., 2009; McMillan, 1993; Naveen, 1999; Polito and Trivelpiece, 2008; Spilsbury and Spilsbury, 2004; Williams, 1995)
On average, gentoo penguins live to be 13 years old. Most deaths occur within the first year of life, with only a 30 to 50 percent chance of surviving until the next year. Beyond the first year, survival increases to an annual rate of 80 percent.
In captivity, the mean life span for P. papau is 10.5 years. Some individuals have lived to be older; however there are many deaths due to weather patterns (for outside exhibits) and for not maintaining a sufficient diet for the penguins. (Gailey-Phipps, 1978; Gilpin, 2007; Williams, 1995)
Gentoo penguins are highly territorial of their nests. For the most part, gentoo penguins live in the same place that they breed. The main reason for moving locations is because of ice formation during the winter months, in which case they will move to an ice-free location.
After the chicks have fledged and made their final departure from the nesting site, adult gentoos begin their annual molt. The pre-molt period begins in January when the adults go out to sea for long foraging trips. They make frequent trips and rapidly gain weight to reach maximum mass at this point of the year. Molting is an energy intensive event, and penguins must gorge themselves to build up fat reserves. This pre-molt period lasts for around 55 days. The actual molting stage lasts 25 days. During this time, P. papau cannot make forages out to sea and must fast, losing about 200 grams a day. Gentoos typically move away from the nesting site to molt. (McMillan, 1993; Williams, 1995)
Gentoo penguins do not defend any territory except the area directly around the nest, averaging 1 square meter in size. (McMillan, 1993)
Visually speaking, gentoo penguins see excellently underwater, although they are impaired when on land. Their retinas are very sensitive to the colors seen underwater such as green, blue, and purple. However this vision becomes impaired once they reach the surface of the water.
Gentoo penguins communicate with each other through a squawking vocalization. These calls typically are higher pitched and louder in males. Gentoos vocalize for a variety of reasons for example, when a male or female returns after feeding they will point their beaks straight up into the air and bellow out squawks to announce their return.
During incubation the parents take turns sitting on the eggs. When the other parent returns (mainly from feeding), a series of displays ensue. The arriving penguin does either a loud display in which he/she bellows out into the air or can do a bowing display in which the penguin bows down to the nest and gives a low hissing sound. Either of these displays communicates to the penguin on the egg that the returning penguin is ready to watch over the nest. The change-over of the nest between parents usually takes three minutes. Sometimes, the displays are reciprocated by the current incubator.
At times during the mating season, the male will rub the female's face and then the two of them will rub their bills together. Also, when one returns to the breeding ground with a stone to use for the nest, the other will bow repeatedly to accept the stone. These displays likely serve to strengthen the pair bond.
Gentoo penguins will also make sounds when another penguin is encroaching on its territory. Gentoos will make low hissing sounds if the interaction is not a high threat level. As a threat looms closer, gentoos will let out grunts.
Chicks communicate with their parents when they want food with high-pitched chirping sounds. In other situations, chicks make a modified whistle call until they reach their first molt where they develop the adult call. Chicks can distinguish their parents call apart from the calls of the thousands of other gentoos that may be nesting within the colony. Like all birds, gentoo penguins perceive their environments through visual, auditory, tactile, and chemical stimuli. (McMillan, 1993; Müller-Schwarze and Müller-Schwarze, 1980; Naveen, 1999; Williams, 1995)
Gentoo penguins are carnivores and mainly consume fish, crustaceans, and cephalopods. Different times of the year mark different percentages of their diet. Krill (Euphausia vallentini) and shrimp (Nauticaris marioni) make up most of the crustacean diet. In February and March, crustaceans make up about 10% of their diet but from March to June it jumps to 75%. All other times of the year, crustaceans are absent from their diet.
From June to October, rockcod (Lepidonotothen squamifrons) make up 90% of their diet, but they also consume unicorn icefish (Channichthys rhinoceratus). Cephalopods only make up 10% of their diet during the year. The main types of cephalopods foraged on are octopi and sometimes small squid. The seasonal diet variation is due the presence of other penguin species during breeding season, seasonal migration of prey, as well as the availability of prey at varying depths. Most other penguins forage in deeper waters which will push some prey species closer to shore and into the prime range for gentoos.
Gentoo penguins feed in shallow regions. When they are underwater, their metabolic rate slows down enabling them to stay underwater for longer periods to forage.
Young chicks are at much greater risk of predation than adults. Brown skuas (Catharacta lonnbergi) are the main predators of penguin chicks. Skuas mainly feed on the chicks and eggs found along the edge of the population which are perceived as weak and solitary. The formation of chick crèches act as an anti-predator-defense. Skuas are less likely to attack the crèches of gentoo chicks because it is hard to distinguish where one chick is within a group.
In the water, waddell seals (Leptonychotes weddellii) have been seen feeding on gentoos. Leopard seals (Hydrurga leptonyx) will travel in the gentoo breeding grounds and attack penguins leaving and returning to the colony. They are most often seen eating chicks as they first enter the water during fledging. Other species of seals such as fur seals from the genus Arctocephalus and southern sea-lions from the genus Otaria have been observed eating gentoos, although their impact on the population is unknown.
The main adaptation to evade predators is countershading. Aquatic predators can look down and see the black dorsal side of the gentoo, which blends in with the ocean floor. Likewise, seals looking up see the white ventral side, which blends in with the light from the sky. (Cobley and Bell, 1998; Emslie, et al., 1995; McMillan, 1993; Williams, 1995)
Gentoos live in colonies with other gentoos, but are also known to live in colonies with other penguin species. Although the species all forage in the ocean, different species are partitioned to forage at different depths or distances. P. papau do not negatively affect other penguin species since they mainly forage right offshore.
Because gentoos live in large colonies with thousands of birds, flea and tick prevalence is high. Fleas from the genus Parapsyllus are common. The most prevalent tick is Ixodes uriae, which mainly affects the exposed skin of chicks such as ear canals, feet, and faces.
Cestodes, members of the genus Tetrabothrius, have been found in the intestines of Pygoscelis papau but little is known about their life cycle. The cestodes are found in various crustaceans that make up the gentoos' diet. Members of the genus Corynosoma also have been reported in gentoos.
Parorchites zederi, another species of cestode, latches onto the inside of gentoos' intestines. These parasites create small pouches in the intestines and insert their pseudoscoleces ("false heads") in them to feed. The areas that P. zederi latch onto increase in volume due to the creation of more intestinal cells and blood flow to the area increases. (Duignan, 2001; Tzvetkov, et al., 1999; Williams, 1995)
Penguins have been hunted for their blubber, which can be purified to oil and used for fuel. Hundreds of thousands of penguins were killed for their blubber, with some breeding colonies becoming obsolete. Gentoo skins are also collected and used to make caps, clothes, slippers, and purses. In the late 1980's, egg collecting was popular by sailors and by locals. These eggs also were consumed in large quantities. (Johnson, 1981; Peterson, 1979; Williams, 1995)
There are no known adverse effects of Pygoscelis papau on humans.
The worldwide gentoo penguin population is stable with around 628,000 individuals. Some of these colonies are increasing moderately while others are declining rapidly. The constant, and sometimes drastic, changes in population size has gentoos listed as "Near Threatened" on the IUCN Red List. There are currently no conservation efforts in action, although some proposals suggest extending long-term observations on breeding colonies to limit disturbances of nesting sites. Protected areas have been set up in gentoo breeding grounds, including those on MacQuarie Island and Heard Island. ("Pygoscelis Papau", 2010; Schafer, 2000)
Kiersten Newtoff (author), Radford University, Karen Powers (editor), Radford University, Rachelle Sterling (editor), Special Projects.
lives on Antarctica, the southernmost continent which sits astride the southern pole.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an animal that mainly eats fish
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sight to communicate
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