Aptenodytes forsteriemperor penguin

Ge­o­graphic Range

Em­peror pen­guins (Apten­odytes forsteri) are found through­out the Antarc­tic con­ti­nent and sub-Antarc­tic is­lands. In breed­ing months (April to No­vem­ber), em­peror pen­guin colonies are found be­tween 66° and 78° south lat­i­tude, along the Antarc­tic coast­line. One colony is lo­cated on the Antarc­tic penin­sula, which is on the west­ern base. Em­peror pen­guins have been recorded on the Islas Malv­inas, and are oc­ca­sional vis­i­tors to Tierra de Fuego (South Amer­ica’s south­ern­most tip) and Isla de Los Es­ta­dos (18km east of Ar­gentina). (Coria and Mon­talti, 2000; Ray­mond, et al., 2015)

Habi­tat

Em­peror pen­guins are ma­rine birds that lives ex­clu­sively in the Antarc­tic. Win­ter tem­per­a­tures there range from -40 to 0°C, with wind chills reach­ing -60°C. Dur­ing their breed­ing sea­son, em­peror pen­guins con­gre­gate on dense sta­ble ice at­tached to the coast­line of Antarc­tica. About 7 to 8 weeks after ju­ve­niles hatch, they leave their colonies and mi­grate to­ward open ocean areas. Out­side of breed­ing sea­son, they spend most of their time in sea­son­ally-packed ice zones, where open sea is eas­ily avail­able for for­ag­ing. Colonies mi­grate to ice shelves dur­ing breed­ing sea­son, where ice cliffs and ice­bergs serve as pro­tec­tion against cross winds. (Kooy­mana, et al., 1990; Ray­mond, et al., 2015; Thiebot and Le­scroel, 2013)

  • Terrestrial Biomes
  • icecap
  • Average elevation
    0 m
    0.00 ft

Phys­i­cal De­scrip­tion

Em­peror pen­guins are the largest sea birds in the Antarc­tic, stand­ing 101 to 132 cm tall. They have wingspans rang­ing from 76 to 89 cm. These pen­guins have black and white bod­ies with stiff black wings. Their back, head, chin, throat, and the dor­sal parts of their wings are black. Their un­der­sides, or ven­tral sides, are com­pletely white up to their necks. They have au­ric­u­lar (ear-re­gion) patches of or­ange and yel­low that fade to­wards their shoul­ders. This yel­low fades to white around the top por­tion of their chest. They also have patches of or­ange and yel­low on their heads and breasts. Em­peror pen­guins have beaks that are long and black, with pink­ish-or­ange stripes along their lower mandibles. Em­peror pen­guins weigh 25 to 45 kg as adults. They gain and lose weight rapidly dur­ing breed­ing and feed­ing sea­sons. On av­er­age, fe­males tend to weigh 18 kg less than males.

When they are born, em­peror pen­guins have gray skin with no feath­ers and weigh around 315 g. Gray feath­ers fill in after the first cou­ple of weeks of birth, after which a black crown of feath­ers going from their bill to the back and sides of their head de­vel­ops. Around the same time, white cheeks and a white chin ap­pear. As ju­ve­niles, em­peror pen­guins are gray­ish-blue, aging as de­vel­op­ing their dis­tinct black-and-white pat­terns as they ma­ture. (Bowles, 1991; Chere, 2008; Kooy­mana, et al., 1990)

  • Sexual Dimorphism
  • male larger
  • Range mass
    25 to 45 kg
    55.07 to 99.12 lb
  • Range length
    101 to 132 cm
    39.76 to 51.97 in
  • Range wingspan
    76 to 89 cm
    29.92 to 35.04 in

Re­pro­duc­tion

Em­peror pen­guins have a monog­a­mous mat­ing sys­tem. A long courtship pe­riod be­gins, last­ing up to 6 weeks, and en­com­passes about 16% of the total breed­ing cycle. Mate pair­ing usu­ally oc­curs in 82% of males and 56% of fe­males within 24 hours of ar­rival to breed­ing grounds. Males and fe­males use vocal calls to find mates. After they bond with a part­ner, em­peror pen­guins no longer vo­cal­ize. This pre­vents dis­tur­bances by other in­di­vid­u­als seek­ing mates. Vocal com­mu­ni­ca­tion re­turns once fe­males lay their eggs. In­di­vid­ual fe­males lay one egg per mat­ing sea­son. (Ancel, et al., 2013; Maho, 1977)

Em­peror pen­guins have an­nual breed­ing cy­cles that are in sync with Antarc­tic sea-ice cy­cles. From Jan­u­ary to March, adults store en­ergy in fat for the up­com­ing breed­ing sea­son, where they fast for a pe­riod of months. Pen­guins ar­rive at breed­ing grounds on sea-ice in early-mid April at the onset of the Antarc­tic win­ter. Pen­guins reach re­pro­duc­tive ma­tu­rity be­tween 4 to 6 years old. Fe­males lay a sin­gle egg in late April or May and pass the egg off to their mate al­most im­me­di­ately. Fe­males then travel ap­prox­i­mately 50 to 120km back to the ocean to find food. Eggs weigh around 450 g – just 2% of the body mass of an adult fe­male. Be­cause they in­cu­bate eggs for a long pe­riod with no food, males lose roughly 40% of their total body mass. Chicks hatch in mid-July, weigh­ing about 315 grams. Be­cause of the harsh con­di­tions, males keep eggs in spe­cial brood pouches. Males feed hatch­lings by pro­duc­ing a nu­tri­ent-rich, milky sub­stance in their esoph­a­gus until fe­males re­turn. De­pend­ing on how far moth­ers have to travel for food, their re­turn may be be­fore the chicks hatch or up to a month there­after. Fe­males lo­cate their mates upon re­turn via vocal searches. Once fe­males re­turn, they take over car­ing for young. After roughly 4 months of fast­ing, males re­turn to the ocean to eat. Fe­males feed their young by re­gur­gi­tat­ing food from their stom­achs. Chicks stay in­side adult brood pouches until they are about a month old. At this age, they start to be­come in­de­pen­dent and in­creas­ingly spend more time out­side of brood pouches. Maho (1977) re­ported chick mor­tal­ity rates of over 90%, with causes in­clud­ing star­va­tion, preda­tors, and harsh weather con­di­tions. By the time chicks are 5 months old they are com­pletely in­de­pen­dent from their par­ents. Chicks molt at this age and are ap­prox­i­mately 50% the size of a full grown adult. Molt­ing is vital for any chance of sur­vival. Chicks leave their par­ents and go off on their own with other chicks. Par­ents also molt and re­turn to sea to start stor­ing up en­ergy for the next breed­ing sea­son. Em­peror pen­guins have a low mate fi­delity rate. Bried et al. (1999) re­ported that only 15% of mates stayed to­gether for mul­ti­ple years, with a max­i­mum time of 4 years. (Ancel, et al., 2009; Ancel, et al., 2013; Bried, et al., 1999; Maho, 1977)

  • Breeding interval
    Emperor penguins breed once yearly.
  • Breeding season
    April-December, Antarctic winter
  • Average eggs per season
    1
  • Average time to hatching
    65 days
  • Average fledging age
    5 months
  • Average time to independence
    5 months
  • Range age at sexual or reproductive maturity (female)
    4 to 6 years
  • Range age at sexual or reproductive maturity (male)
    4 to 6 years

Em­peror pen­guins rely on their par­ents until in­de­pen­dence – around 5 months of age. Males in­cu­bate and pro­tect eggs in their brood pouches, a spe­cial­ized skin fold on their lower ab­domens. They do this for roughly 65 days, or until fe­males have re­turned. When chicks are born, they live solely un­der­neath the brood pouches of the males. They are fed a nu­tri­ent-rich, milky sub­stance that is se­creted in the esoph­a­gus. When the fe­males re­turn, they take over car­ing and feed­ing their off­spring by re­gur­gi­tat­ing food from their stom­achs. Both males and fe­males take turns going to and from the ocean to for­age, bring­ing their off­spring food until they are 5 months old. At this point, chicks leave their par­ents and molt their ju­ve­nile feath­ers in prepa­ra­tion to start div­ing for their own food. (Ancel, et al., 2009; Bried, et al., 1999; Maho, 1977)

  • Parental Investment
  • male parental care
  • female parental care
  • pre-hatching/birth
    • provisioning
      • male
    • protecting
      • male
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifes­pan/Longevity

Em­peror pen­guins have a lifes­pan ex­pectancy in the wild of 15 to 20 years, but some re­searchers sug­gest that in­di­vid­u­als have lived to up to 50 years. How­ever, re­search sug­gests that only 1% of pen­guins reach such an age. Pen­guins in cap­tiv­ity have a lifes­pan of 20 to 34 years.

De­pend­ing on en­vi­ron­men­tal and cli­mate fac­tors, sur­vival rates of chicks in their first year varies, with 20% of chicks mak­ing it past the first year on av­er­age. Maho (1977) re­ported chick mor­tal­ity to be over 90% in their first year, with causes in­clud­ing star­va­tion, pre­da­tion, and harsh weather con­di­tions. An­nual sur­vival rates for adult em­peror pen­guins are around 95.1%. An­nual av­er­age sea sur­face tem­per­a­ture is a fac­tor that has been shown to in­flu­ence adult sur­vival. Em­peror pen­guins sur­vived less when sur­face tem­per­a­tures were higher, roughly be­tween -24°C and 10°C. (Ain­ley, et al., 2012; Bar­braud and Weimer­skirch, 2001; Maho, 1977)

  • Range lifespan
    Status: captivity
    50 (high) years
  • Typical lifespan
    Status: wild
    15 to 20 years
  • Typical lifespan
    Status: captivity
    20 to 34 years

Be­hav­ior

Em­peror pen­guins dis­play com­mon be­hav­iors char­ac­ter­is­tic of many seabird species, how­ever there are be­hav­iors unique to this species. Dur­ing breed­ing and in­cu­ba­tion pe­ri­ods in harsh Antarc­tic weather con­di­tions, groups of pen­guins hud­dle as a way to con­serve en­ergy. Hud­dles may be small – less than 200 birds – or as large as 5,000 or 6,000 birds. The av­er­age du­ra­tion of hud­dles av­er­ages 1.6 hours. Pen­guins in hud­dles make small, con­tin­u­ous move­ments, al­ter­nately get­ting closer to each other and break­ing apart. This pre­serves en­ergy and al­lows these pen­guins to fast for long pe­ri­ods of time. Ancel et al. (2009) re­port that 84% of mate pairs stay to­gether dur­ing hud­dling events. Ex­actly how part­ners stayed to­gether is not known. Chicks in groups, known as a crèche, also hud­dle to stay warm and con­serve en­ergy.

Em­peror pen­guins also lie down, which helps lower meta­bolic rate and con­serve en­ergy in harsh Antarc­tic con­di­tions. This in­di­vid­ual be­hav­ior de­creases the amount of body sur­face area ex­posed to cold air, min­i­miz­ing heat loss due to high-speed winds. Ground-level snow also acts like a wind bar­rier. Dur­ing in­cu­ba­tion pe­ri­ods, males re­main nearly mo­tion­less for days at a time to de­crease their meta­bolic rates. Their stance has adapted in such way to min­i­mize heat loss. They stand on 3 rest­ing points: their 2 heels, and tail. The plan­tar sur­faces of their feet do not touch the ground, min­i­miz­ing heat loss to the ground. The rest of their body is sit­u­ated in such way to pre­vent freez­ing. They tuck their heads to their chests and press their flip­pers tightly against their bod­ies. In breed­ing sea­son, mat­ing pairs use vocal songs as a demon­stra­tion of their part­ner­ship. Pen­guins use these vocal songs to lo­cate their mates when they re­turn from the ocean dur­ing breed­ing sea­son. Chicks also use calls to lo­cate their par­ents. (Ancel, et al., 2009; Bried, et al., 1999; Maho, 1977)

Home Range

No home range has been pub­lished for em­peror pen­guins, and An­drews et al. (2008) re­port that that they don't have one. They do not de­fend a ter­ri­tory. (Ancel, et al., 2013; An­drews, et al., 2008)

Com­mu­ni­ca­tion and Per­cep­tion

Em­peror pen­guins are a rel­a­tively vocal bird that use dif­fer­ent fre­quen­cies for mate pair­ing, mate recog­ni­tion, and off­spring/par­ent recog­ni­tion. Most vocal com­mu­ni­ca­tion is trans­mit­ted through a pair of dif­fer­ent fre­quen­cies. Dis­play calls are di­rected to­wards spe­cific in­di­vid­u­als, for ex­am­ple in-be­tween mates. Mates rely on these spe­cial­ized vocal calls dur­ing the breed­ing sea­sons to lo­cate each other, be­cause they spend the ma­jor­ity of their time apart. Par­ents and off­spring also use calls to iden­tify each other. Chicks also use high fre­quency whis­tles to tell their par­ents when they are hun­gry. In order for chicks to be fed, they must rec­og­nize and re­spond to their par­ents calls. Non-ver­bal move­ments are also used for com­mu­ni­ca­tion. Par­ents teach their off­spring how to swim and feed. Em­peror pen­guins also a non-ver­bal pos­ture to com­mu­ni­cate be­tween other in­di­vid­u­als. They fre­quently stand in an ob­vi­ous pos­ture with their bills turned up and wings slightly out in order to avoid ag­gres­sion. (Bried, et al., 1999; Burns and Kooy­man, 2001; Maho, 1977; Young, 1994)

  • Other Communication Modes
  • mimicry

Food Habits

Em­peror pen­guins are car­niv­o­rous and pri­mar­ily feed on fish, crus­taceans, and mol­luscs. They feed on fish and krill the most, as they are most abun­dant in the ocean sur­round­ing Antarc­tica. Em­peror pen­guins have a rough and spiky-tex­tured tongue, which helps them catch and eat slip­pery fish and squids more eas­ily. Prey abun­dance varies from lo­ca­tion to lo­ca­tion, but some re­search has found that the Antarc­tic sil­ver­fish (Pleura­gramma antarcticum) is one of the most fre­quently con­sumed species. Fish from the fam­ily No­totheni­idae are also con­sumed as a sta­ple of their diet. Mol­luscs such as the glacial squid (Psy­chro­teuthis glacialis), hooked squid (Kon­dakovia longi­mana), and the Antarc­tic krill (Eu­phau­sia su­perba) are also eaten reg­u­larly. They feed in the open wa­ters of the ocean sur­round­ing Antarc­tica, or un­der­neath sea ice. They can dive to depths of up to 500 m. They can stay under for over 15 min­utes and may travel up to 1000 km in one dive. Stay­ing in the sea for un­nec­es­sary lengths of time in­creases their chance to be at­tacked by prey, so they tend to stay closer to the sur­face as long as food is plen­ti­ful. They can travel up to 20 km/hr in the water, how­ever they gen­er­ally travel around 10 km/hr. Some ob­ser­va­tions sug­gest that groups of pen­guins co­or­di­nate their dives and hunt co­op­er­a­tively. An adult pen­guin eats 2 to 3 kg per day. How­ever, be­fore the long fast­ing breed­ing sea­son, they tend to eat up to 6 kg per day. Chicks rely solely on their par­ents for food for the first 5 months of their lives, and typ­i­cally re­quire an av­er­age of 84 kg of food dur­ing those months. (Ain­ley, et al., 2012; Ancel, et al., 2009; LaRue, et al., 2015; Lengagne, et al., 2001)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Pre­da­tion

Em­peror pen­guins are one of the top preda­tors in the Antarc­tic ma­rine en­vi­ron­ment. Killer whales (Or­ci­nus orca) have been ob­served to prey on em­peror pen­guins, some­times ha­rass­ing them for fun. Leop­ard seals (Hy­drurga lep­tonyx) are also ma­rine preda­tors of pen­guins, and have been ob­served to kill em­peror pen­guins. How­ever, re­search shows that em­peror pen­guins are not a part of their sta­ple diet. Be­cause of their large size, em­peror pen­guins may be un­fa­vor­able to killer whales and leop­ard seals, pro­vided smaller pen­guins are abun­dant. How­ever, ob­ser­va­tions by Kooy­mana et al. (1990) did ob­serve adults and chicks being heav­ily preyed upon by leop­ard seals. This may have been be­cause few other food sources were avail­able. Seabirds called skuas (Ster­co­rar­ium par­a­siti­cus) are also known to steal and eat em­peror pen­guin eggs and chicks. Lit­tle is known about how pen­guins pro­tect them­selves from preda­tors. Most em­peror dives are shal­low and fairly quick, which makes it harder for preda­tors to reach them be­fore they are out of the water again. In ad­di­tion to a large pointed beak, their feath­ers and shape of their body also likely func­tion as pro­tec­tion from preda­tors. With black backs and white bel­lies, em­peror pen­guins are coun­ter­shaded. This makes it harder to dis­tin­guish their form while they are swim­ming. (An­drews, et al., 2008; Chere, 2008; Kooy­mana, et al., 1990; Maho, 1977)

Ecosys­tem Roles

Bar­bosa and Pala­cios (2009) found that wild em­peror pen­guins are a com­mon host for sev­eral gas­tro-in­testi­nal par­a­sites, in­clud­ing the tape­worms Tetra­both­rius wright and Paror­chites zed­eri.

Klenin­ertz et al. (2014) found that 26% of a small pop­u­la­tion of em­peror pen­guins at the Atka Bay in Antarc­tica were par­a­sitized by a par­a­sitic ne­ma­tode or round­worm of the fam­ily Cap­il­lari­idae, along with tape­worms in the gen­era Tetra­both­rius and Di­phyl­loboth­rium. Paror­chites zed­eri was found in their feces. The par­a­sitic louse species Aus­tro­go­niodes maw­soni has also been found to use em­peror pen­guins as a host. (An­drews, et al., 2008; Bar­bosa and Pala­cios, 2009; Chere, 2008; Klein­ertz, et al., 2014; Kooy­mana, et al., 1990; Maho, 1977)

Com­men­sal/Par­a­sitic Species

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Re­searchers study em­peror pen­guins in order to un­der­stand the phys­i­cal and be­hav­ioral adap­ta­tions that allow them to with­stand ex­tremely cold tem­per­a­tures. Em­peror pen­guins also at­tract tourists to the Antarc­tic. Many or­ga­ni­za­tions and com­pa­nies offer day trips to var­i­ous areas for em­peror sight­see­ing in­clud­ing overnight trips. (Ray­mond, et al., 2015; Thiebot and Le­scroel, 2013)

  • Positive Impacts
  • ecotourism
  • research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known neg­a­tive im­pacts of em­peror pen­guins on hu­mans.

Con­ser­va­tion Sta­tus

Em­peror pen­guins are con­sid­ered a near threat­ened species on the IUCN red list. Their pop­u­la­tions are pro­jected to rapidly de­cline about 27% over the next three gen­er­a­tions (ap­prox. 61 years) due to cli­mate change. Cur­rently, the pop­u­la­tion is con­sid­ered sta­ble, with ca. 476,000 in­di­vid­u­als. The list­ing sta­tus of em­peror pen­guins is under re­view to be re-listed as threat­ened or en­dan­gered by the U.S. Fish and Wildlife Ser­vice. There is on­go­ing in­ter­na­tional re­search of em­peror pen­guins to pre­dict what will hap­pen to these birds if the cli­mate con­tin­ues to change. Re­searchers pre­dict that, be­tween the years of 2025 and 2052, all em­peror pen­guin colonies north of 67°S will have dis­ap­peared due to lack of sea ice, caused by a warm­ing cli­mate.

Human prox­im­ity also poses a threat to em­peror pen­guins. Dur­ing the sum­mer months, when em­peror pen­guins are for­ag­ing at sea, the great­est amount of tourism takes place. On­go­ing re­search is ex­am­in­ing ori­gins of dis­eases in­clud­ing in­fec­tious bur­sal dis­ease virus, New­cas­tle dis­ease, and avian in­fluenza. Many re­searches sus­pect that these dis­eases were brought to Antarc­tica by hu­mans that are now harm­ing pen­guins and other Antarc­tic an­i­mals. (Ain­ley, et al., 2012; Bar­braud and Weimer­skirch, 2001; Boersma, 2008)

Con­trib­u­tors

Sarah Wilber (au­thor), Rad­ford Uni­ver­sity - Fall 2015, Karen Pow­ers (ed­i­tor), Rad­ford Uni­ver­sity, April Tin­gle (ed­i­tor), Rad­ford Uni­ver­sity, Cari Mc­gre­gor (ed­i­tor), Rad­ford Uni­ver­sity, Zeb Pike (ed­i­tor), Rad­ford Uni­ver­sity, Jacob Vaught (ed­i­tor), Rad­ford Uni­ver­sity, Galen Bur­rell (ed­i­tor), Spe­cial Pro­jects.

Glossary

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

acoustic

uses sound to communicate

bilateral symmetry

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

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.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

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.

female parental care

parental care is carried out by females

iteroparous

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).

male parental care

parental care is carried out by males

mimicry

imitates a communication signal or appearance of another kind of organism

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polar

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.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

visual

uses sight to communicate

Ref­er­ences

Ain­ley, D., G. Kooy­man, P. Trathan, E. Woehler. 2012. "Apten­odytes forsteri" (On-line). The IUCN Red List Of Threat­ened Species. Ac­cessed No­vem­ber 04, 2015 at http://​www.​iucnredlist.​org/​details/​full/​22697752/​0.

Ancel, A., C. Gilbert, M. Beaulieu. 2013. The long en­gage­ment of the em­peror pen­guin. Polar Bi­ol­ogy, 36/4: 573-577.

Ancel, A., M. Beaulieu, Y. Maho, C. Gilbert. 2009. Em­peror pen­guin mates:Keep­ing to­gether in the crowd. Pro­ceed­ings of the Royal So­ci­ety B, 276/1665: 2163-2169.

An­drews, R., R. Pit­man, L. Bal­lance. 2008. Satel­lite track­ing re­veals dis­tinct move­ment pat­terns for type b and Type c killer whales in the south­ern Ross Sea, Antarc­tica. Polar Bi­ol­ogy, 31/12: 1461-1468.

Bar­bosa, A., M. Pala­cios. 2009. Health of Antarc­tic birds: A re­view of their par­a­sites, pathogens, and dis­eases. Polar Bi­ol­ogy, 32/8: 1095-1115.

Bar­braud, C., H. Weimer­skirch. 2001. Em­peror pen­guin and cli­mate change. Na­ture, 32/410: 183-186.

Boersma, D. 2008. Pen­guins as ma­rine sen­tinels. Bio­Science, 58/7: 597-607.

Bowles, A. 1991. Recog­ni­tion of fa­mil­iar calls by the em­peror pen­guin (Apten­odytes forsteri)−how im­por­tant are call tim­ing, spec­tral char­ac­ter­is­tics, and fre­quency mod­u­la­tion?. The Jour­nal of Acousti­cal So­ci­ety of Amer­ica, 90/4: 2335.

Bried, J., F. Jiguet, P. Jou­ventin. 1999. Why do Apten­odytes pen­guins have high di­vorce rates?. The Auk, 116/2: 504-512.

Burns, J., G. Kooy­man. 2001. Habi­tat use by Wed­dell seals and em­peror pen­guins for­ag­ing in the Ross Sea, Antarc­tica. In­te­gra­tive and Com­par­a­tive Bi­ol­ogy, 42/1: 90-98.

Chere, Y. 2008. Iso­topic niches of em­peror and Adélie pen­guins in Adélie Land, Antarc­tica. Ma­rine Bi­ol­ogy, 154/5: 813-821.

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