Humboldt penguin

The Humboldt penguin (Spheniscus humboldti) is a South American penguin living mainly in the Pinguino de Humbold National Reserve in the North of Chile, although its habitat comprises most of coastal Chile and Peru.[2] Its nearest relatives are the African penguin, the Magellanic penguin and the Galápagos penguin. The Humboldt penguin and the cold water current it swims in both are named after the explorer Alexander von Humboldt. The species is listed as vulnerable by the IUCN with no population recovery plan in place.[3] The current population is composed of 32,000 mature individuals and is going down.[4] It is a migrant species.[4]

Humboldt penguin
At Islas Ballestas, Peru
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Sphenisciformes
Family: Spheniscidae
Genus: Spheniscus
Species:
S. humboldti
Binomial name
Spheniscus humboldti
Meyen, 1834
Distribution of the Humboldt penguin. 80% of the world's population lives in the protected areas of the Northern Chilean regions III and IV

Humboldt penguins are medium-sized penguins, growing to 56–70 cm (22–28 in) long and a weight of 3.6-5.9 kg (8-13 lbs).[5][6] They have a black head with a white border that runs from behind the eye, around the black ear-coverts and chin, and joins at the throat. They have blackish-grey upperparts and whitish underparts, with a black breast-band that extends down the flanks to the thigh. They have a fleshy-pink base to the bill. Juveniles have dark heads and no breast-band. They have spines on their tongue which they use to hold their prey.

Humboldt penguins nest on islands and rocky coasts, burrowing holes in guano and sometimes using scrapes or caves. In South America the Humboldt penguin is found only along the Pacific coast,[7] and the range of the Humboldt penguin overlaps that of the Magellanic penguin on the central Chilean coast. It is vagrant in Ecuador and Colombia.[8] The Humboldt penguin has been known to live in mixed species colonies with the Magellanic penguin in at least two different locations at the south of Chile.[9][10]

The Humboldt penguin has become a focus of ecotourism over the last decades.[11]

Etymology

Both the Humboldt penguin and the Humboldt current were named after Alexander von Humboldt. It is known in Peru as the "pajaro-niño", which translates to "baby-bird", due to their waddling gait and flightless wings held out suggesting the image of an infant toddling on the beach.[12]

Distribution and habitat

The Humboldt penguin is a top predator endemic to the west coast of South America.[13][14]

The Humboldt penguin's breeding distribution ranges from southern Chile along the dry and arid coastal regions of the Atacama Desert to subtropical Isla Foca in north Peru. Its range is restricted to the coast and offshore islands affected by the Humboldt current, which provides a continuous supply of nutrients and food, thus supporting huge populations of seabird.[15] In Chile, the most important breeding colony is at Isla Chañaral.[13]

Ecology

Diet

The Humboldt penguin feeds predominantly on pelagic schooling fish.[16] The consumption of cephalopods and crustaceans vary between populations.[17] Northern colonies consume primarily garfish, whilst southern populations primarily consume anchovy, Araucanian herring and silver-side.[17] There are seasonal differences in the Humboldt penguin's diet that reflect the changes in availability of fish species across seasons.[17]

Foraging behaviour

The Humboldt penguin is a visual hunter.[18] Humboldt penguins leave their islands for foraging after sunrise and different populations have different preferred foraging distances from the colony.[16] Their foraging rhythm depends on the light intensity.[19] They spend more time foraging during overnight trips.[20] Fish are mostly seized from below through short, shallow dives.[16]

The foraging range of Humboldt penguins is between 2 and 92 km from Pan de Azúcar, with 90% of the foraging being from a range of 35 km around the island and 50% from a range of 5 km.[17] The maximum depth reached is 54m.[14]

Failed breeders take longer foraging trips with longer and deeper dives.[21] They also dive less often than breeding penguins.

Vocalisation

The Humboldt penguin has different calls that it uses to communicate in different ways. The function of its calls are consistent among Spheniscus species.

If an individual comes too close to an adult Humboldt penguin, the Yell is a warning call which is followed by pecking or chasing if ignored.[22] A higher density of penguins leads to more territorial and aggressive behaviours, which leads to more Yells.[22]

The Throb is a soft call between pairs at the nest, used by incubating birds when their mates return to the nest.[22]

The Haw is a short call given by juveniles alone in the water and by paired birds when one is on the water and the other is on land.[22] It has significant individual variation in duration and frequency.[22]

The Bray is a long call used to attract a mate and advertise a territory during the pre-laying and pre-hatching periods.[22] It is an individually distinct call in all variables: syllables per call, duration, inter-syllable intervals, duration of syllables and frequency.[22] When calling, the bird points its head upwards and flaps its flippers slowly when calling.[22]

The Courtship Bray is similar to the Bray, however a different posture is assumed and is given synchronously by pairs during the pre-laying period: the birds stand together pointing their necks and head up, with flippers out to the side.[22]

The Peep is given by chicks begging for food.[22]

Moulting

Most penguins moult between mid-January and mid-February, however the initiation varies with latitude and favourable conditions such as food abundance.[23][24] Humboldt penguins are confined to land until they finish moulting.[13] They become hyperphagic during the pre-moulting period.[24] The feathers are lost and replaced within 2 weeks.[25]

Sex dimorphism

The sex of the Humboldt penguin cannot be recognised via differences in plumage, as they are monomorphic. The male is heavier and larger than the females.[26] Their sex can be determined via head width and bill length; the male has a longer bill than the female.[26]

Courtship

During courtship, the Humboldt penguins bow their heads to each other and exchange mutual glances with each eye, alternatively.[27] In the ecstatic display to attract a partner, the bird extends its head vertically, collapses its chest, flaps its wings and emits a loud call resembling the braying of a donkey.[25] The mutual displaying consist of the pair standing side by side and repeating the actions of the ecstatic display.[25]

Reproduction

The Humboldt penguin nests in loose colonies, with most pairs laying two eggs of the same size 4 days apart that require 41 days of incubation.[28][14] Their breeding schedule is adjusted depending on the abundance of food.[24] They breed immediately after moulting, when food is abundant and solar radiation is reduced.[24]

The Humboldt penguin lay eggs from March to December, but also with peaks in April and August–September, due to individuals having a second clutch.[28][24] Half of the females successfully have two clutches per year and most were double broods.[27][28][24] If pairs lose their eggs during the first breeding season, they lay a new clutch within 1–4 months.[28] The incubation shifts last, on average, 2.5 days, before one parent takes over and allows the other to forage.[20] There are no differences in the contribution to provisioning from the male and female parents.[20]

Chicks hatch generally 2 days apart.[28] Chicks are semi-altricial and nidicolous and guarded by one parent while the other forages.[14] Chicks are fed only once every day.[28] Chicks are left unattended at the nest site after a certain age and both parents forage simultaneously.[14]

Breeding sites

The historical breeding sites of this species are burrows on guano layers.[27] Nests of the Humboldt penguin can also be found at caverns, hollows, cliff tops, beaches and scrapes covered by vegetation.[12][28] They also nest at few Peruvian islands where true soil can be found for digging.[27] The majority of penguins breed on cliff tops.[28]

Migration

Humboldt penguins are sedentary during the breeding season, staying in proximity to their nests and show fidelity to breeding site.[14][28] They can cover large distances, particularly in response to food shortages or changes in environmental conditions.[29][14] They are a true migrant between Peru and Chile.[29]

Threats

El Niño-La Niña dynamics

The ecosystem of the Humboldt current is affected by the El Niño phenomenon. During the El Niño, upwelling of nutrient-rich bottom water in the south-eastern Pacific Ocean is depressed, as well as sea surface temperature anomaly (SSTA) value increases.[30][14] Massive mortality, especially of juveniles, nest desertion and lack of reproduction occurs.[30] Humboldt penguins migrate south as marine productivity decreases, following the anchovy stocks.[14] Humboldt penguins expend more time and energy foraging as SSTA increases.[14]

Fisheries

The estimated energetic demands of the total Humboldt penguin population during breeding season sums up to 1,400 tons of fish.[17] The Humboldt penguin depends on commercially exploited, schooling prey species.[17] This makes them susceptible to changes in prey stocks due to non-sustainable fisheries management.[17] They are also susceptible to entanglement in fishing nets.[31]

Human presence

Humboldt penguins are extremely sensitive to human presence, with little habituation potential.[11] Passing at a 150m distance from an incubating Humboldt penguin provokes a response, which is the greatest response distance reported for penguins to date, making it the most timid penguin species so far studied.[11] Humboldt penguins need up to half an hour to recover to normal heart rates after human approach, however, this time decreases with repeated visitation.[11] Cumulative stress by frequent visits and delayed return of foraging partners leads to nest desertion, consequently causing decreased breeding success at frequently visited sites.[11][19]

Habitat disturbance and feral species

The introduction of feral goats on the Puñihuil islands had a detrimental impact on the Humboldt penguin population.[9] The feral goats browse the vegetation the penguins use to build their nests and they can lead to collapse to dirt burrows.[9] The connection of the island to the mainland also led to the movements of mammals onto the island.[9]

In central Chile, European rabbits and Norway rats graze on the vegetation.[32] Norway rats and black rats also predate on eggs.[33] Feral cats and dogs consume chicks, fledgelings and adult Humboldt penguins.[32]

History of Population Decline

Over-exploitation of guano

The historical breeding grounds for the Humboldt penguin were guano layers which covered islands of the Peruvian and northerly Chilean coasts in which the birds could burrow.[27] The guano, a rich fertiliser and source of income for the Peruvian Government, and eggs of the Humboldt penguin were regularly sought after.[34][12][27] The birds were also frequently killed by fishermen and guano workers for their oil and skin.[12] The decline of the Humboldt penguin population is attributed to the harvest of guano in the 1800s, which led to the destruction of breeding grounds and to human disturbance.[30][12]

1982-83 El Niño phenomenon

Before the 1982-83 El Niño event, the total number of individuals of Humboldt penguin individuals was estimated to be 20,000.[30] The 1982-83 El Niño phenomenon led to a major decline in the Humboldt penguin population.[30] The combination of an environment changed by human developments as well as the long duration and strong intensity of the event that year led to major effects on the fecundity and survival of the Humboldt penguins.[30] The consequences were a 65% decline in the Humboldt penguin population, migration towards the south and the failure of the 1982 class of hatchlings.[30] The surviving population in 1984 was estimated to be between 2,100 and 3,000 penguins and all were adults.[30]

Conservation

Due to a declining population caused in part by over-fishing, climate change, and ocean acidification, the current status of the Humboldt penguin is threatened.[35] Humboldt penguins were given legal protection in 1977 by the Peruvian Government and listed in Appendix I of the Convention of International Trade of Endangered Species (CITES).[36] Both Peru and Chile have implemented the CITES under national law.[36] It is categorised as vulnerable due to extreme population size fluctuations, clustered distribution and the major threats to the species not being ameliorated over time.[36][4][37] In August 2010 the Humboldt penguin of Chile and Peru, was granted protection under the U.S. Endangered Species Act.[35] Most penguins breed within protected areas.[37]

Peruvian legislation categorises the species as endangered and prohibits the hunting, possession, capture, transportation and export of the bird for commercial purposes.[37] Chile implemented a 30-year hunting ban in 1995 forbidding hunting, transport, possession and commercialisation of penguins.[37]

In 2017 a large mining project proposed by the company Andes Iron in Chile was vetoed due to the possible environmental impact on the penguins.[38]

In captivity

In addition to their home waters near South America, Humboldt penguins can be found in zoos all around the world, including Spain, Germany,[39] India, Ireland,[40][41] Japan,[42] the United Kingdom,[43] the United States[44] and other locations.

Escape from Tokyo Zoo

One of the 135 Humboldt penguins from Tokyo Sea Life Park (Kasai Rinkai Suizokuen) thrived in Tokyo Bay for 82 days after apparently scaling the 4-metre-high wall and managing to get through a barbed-wire fence into the bay.[45] The penguin, known only by its number (337), was recaptured by the zoo keepers in late May 2012.[46]

USA discovery

In 1953, a Humboldt penguin was found in The Bronx, USA. It is not known whether the animal had escaped from a private collection or whether it was a vagrant but the local zoo's population was fully accounted for.[47]

Same-sex raising of young

In 2009 at the Bremerhaven Zoo in Germany, two adult male Humboldt penguins adopted an egg that had been abandoned by its biological parents. After the egg hatched, the two penguins raised, protected, cared for, and fed the chick in the same manner that heterosexual penguin couples raise their own offspring. A further example of this kind of behavior came in 2014, when Jumbs and Kermit, two Humboldt Penguins at Wingham Wildlife Park became the center of international media attention as two males who had pair bonded a number of years earlier and then successfully hatched and reared an egg given to them as surrogate parents after the mother abandoned it halfway through incubation.[48]

in captivity at Brookfield Zoo

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