Pinguino africano

Identificazione

African penguins grow to 60–70 cm (24–28 in) tall and weigh between 2.2–3.5 kg (4.9–7.7 lb). The beak length of the African penguin varies, usually growing between 20–30 cm (7.9–11.8 in). They have a black stripe and black spots on the chest, the pattern of which is unique to each penguin, like human fingerprints. The sweat glands above the eyes cool the birds' blood and as the temperature rises, increased blood flow causes the glands to get pinker. This species exhibits slight sexual dimorphism; the males are slightly larger than the females and have longer beaks. Juveniles do not possess the bold, delineated markings of the adult, but instead have dark upperparts that vary from greyish-blue to brown; the pale underparts lack both spots and the band. The beak is more pointed than that of the Humboldt penguin. The African penguin's colouring is a form of protective colouration known as countershading. The white undersides of the birds are difficult to spot by predators under the water and the penguins' black backs blend in with the water when viewed from above.<p>African penguins resemble and are thought to be related to the Humboldt, Magellanic and Galápagos penguins. African penguins have a very recognisable appearance, with a thick band of black that is in the shape of an upside-down horseshoe. They have black feet and black spots that vary in size and shape between individuals. Magellanic penguins share a similar bar marking that often confuses the two; the Magellanic has a double bar on the throat and chest, whereas the African has a single bar. These penguins have the nickname "jackass penguin", which comes from the loud penguin noises they make.

Tassonomia

In 1747, the English naturalist George Edwards included an illustration and a description of the African penguin in the second volume of his A Natural History of Uncommon Birds. He used the English name "The Black-Footed Penguins". Edwards based his hand-coloured etching on two preserved specimens that had been brought to London. He suspected that they had been collected near the Cape of Good Hope. When in 1758 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the tenth edition, he placed the African penguin with the wandering albatross in the genus Diomedea. Linnaeus included a brief description, coined the binomial name Diomedea demersa and cited Edwards' work. The African penguin is now placed with the banded penguins in the genus Spheniscus that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson. The genus name Spheniscus is from Ancient Greek word σφήν (sphēn) meaning "wedge" and is a reference to the animal's thin, wedge-shaped flippers. The specific epithet demersus is Latin meaning "plunging" (from demergere meaning "to sink").<p>Banded penguins are found mainly in the Southern Hemisphere with the Humboldt penguin and Magellanic penguins found in southern South America and the Galápagos penguin found in the Pacific Ocean near the equator. All are similar in shape, colour and behaviour.

Nome scientifico

Spheniscus demersus

Autorità

(Linnaeus, 1758)

Ordine

Sfenisciformi

Famiglia

Spheniscidae

Genere

Spheniscus

Areale e habitat

The African penguin is only found on the southwestern coast of Africa, living in colonies on 24 islands between Namibia and Algoa Bay, near Port Elizabeth, South Africa. It is the only penguin species that breeds in Africa and its presence gave name to the Penguin Islands.<p>Two colonies were established by penguins in the 1980s on the mainland near Cape Town, namely Boulders Beach near Simon's Town and Stony Point in Betty's Bay. Mainland colonies likely became possible only in recent times due to the reduction of predator numbers, although the Betty's Bay colony has been attacked by leopards. The only other mainland colony is in Namibia, but it is not known when it was established.<p>Boulders Beach is a tourist attraction due to the beach, swimming and the penguins. The penguins will allow people to approach them as close as a meter.<p>Breeding populations of African penguins are being kept in numerous zoos worldwide. No colonies are known outside the southwestern coast of Africa, although vagrants (mostly juveniles) may occasionally be sighted beyond the normal range.<p>Roughly 4 million African penguins existed at the beginning of the 19th century. Of the 1.5 million African penguins estimated in 1910, only some 10% remained at the end of the 20th century. African penguin populations, which breed in Namibia and South Africa, have declined by 95% since pre-industrial times.<p>Today, their breeding is largely restricted to 24 islands from Namibia to Algoa Bay, South Africa, with the Boulders Beach colony being an exception to this rule.<p>The total population fell to approximately 150,000–180,000 in 2000. Of those, 56,000 belonged to the Dassen Island colony and 14,000 to the Robben Island colony. The colony at Dyer Island in South Africa fell from 46,000 in the early 1970s to 3,000 in 2008.<p>In 2008, 5,000 breeding pairs were estimated to live in Namibia.<p>In 2010, the total African penguin population was estimated at 55,000. At the rate of decline seen from 2000 to 2010, the African penguin is expected to be extinct in the wild by 2026.<p>In 2012, about 18,700 breeding pairs were estimated to live in South Africa, with the majority on St. Croix Island in Algoa Bay.<p>The total breeding population across both South Africa and Namibia fell to a historic low of about 20,850 pairs in 2019.

Areale riproduttivo

AF : coastal s Namibia and s South Africa

Areale non riproduttivo

to c Namibia, se Africa

Migrazione

Resident species

Comportamento

African penguins forage in the open sea, where they feed on pelagic fish such as sardines (including the blue pilchard), Cape horse mackerels, red-eye round herrings and anchovies (specifically the European anchovy and the Southern African anchovy) and marine invertebrates such as squids and small crustaceans, primarily krills and shrimps. Penguins normally swim within 20 km (12 mi) of the shore. A penguin may consume up to 540 grams (1.19 lb) of prey every day, but this may increase to over 1 kg (2.2 lb) when raising older chicks.<p>Due to the marked decline of sardines in the waters near its habitat, African penguins' diet has shifted towards anchovies to some extent, although available sardine biomass is still a notable determinant of penguin population development and breeding success. While a diet of anchovies appears to be generally sufficient for the penguins, it is not ideal due to anchovies' lower concentrations of fat and protein. The Penguin's diet changes throughout the year; as in many seabirds, it is believed that the interaction of diet choice and breeding success helps the penguins maintain their population size. Although parent penguins are protective of their chicks, they will not incur nutritional deficits themselves if food is scarce and hunting requires a greater time or energy commitment. This may lead to higher rates of brood loss under poor food conditions.<p>When foraging, African penguins carry out dives that reach an average depth of 25 m (82 ft) and last for 69 seconds, although a maximum depth of 130 m (430 ft) and duration of 275 seconds has been recorded.<p>The African penguin is monogamous; it breeds in colonies and pairs return to the same site each year. It has an extended breeding season, with nesting usually peaking from March to May in South Africa and November to December in Namibia. A clutch of two eggs is laid either in burrows burrowed in guano or nests in the sand under boulders or bushes. Incubation is undertaken equally by both parents for around 40 days. At least one parent guards the chicks for about one month, whereafter the chicks join a crèche with other chicks and both parents spend most of the day foraging in the sea.<p>Chicks fledge at 60 to 130 days, the timing depending on environmental factors such as the quality and availability of food. The fledged chicks then go to sea on their own, where they spend the next one to nearly two years. They then return to their natal colony to moult into adult plumage.<p>When penguins moult, they are unable to forage in the sea as their new feathers are not yet waterproof; therefore, they fast over the entire moulting period. African penguins typically take around three weeks to moult and lose about half of their body weight by burning up their fat reserves in the process.<p>African penguins spend most of their lives at sea until it comes time for them to lay their eggs. Females remain fertile for about 10 years. Due to high predation on the mainland, African penguins will seek protection on offshore islands, where they are safer from larger mammals and natural challenges. These penguins usually breed during the winter when temperatures are cooler. African penguins often will abandon their eggs if they become overheated in the hot sun and abandoned eggs never survive the heat. The eggs are three to four times bigger than chicken eggs. Ideally, the eggs are incubated in a burrow dug into the guano layer (which provides suitable temperature regulation), but the widespread human removal of guano deposits has rendered this type of nest unfeasible in many colonies. To compensate, penguins burrow holes in the sand, nest under rocks or bushes or make use of nest boxes if they are provided. The penguins spend three weeks on land caring for their offspring, after which chicks may be left alone during the day while the parents forage. The chicks are frequently killed by predators or succumb to the hot sun. Parents usually feed hatchlings during dusk or dawn.<p>In 2015, when foraging conditions were favourable, more male than female African penguin chicks were produced in the colony on Bird Island. Male chicks also had higher growth rates and fledging mass and therefore may have higher post-fledging survival than females. This, coupled with higher adult female mortality in this species, may result in a male-biased adult sex ratio and may indicate that conservation strategies focused on benefiting female African penguins may be necessary.<p>The average lifespan of an African penguin is 10 to around 25 years in the wild and up to 30 in captivity.<p>The primary predators of African penguins at sea include sharks and fur seals. While nesting: kelp gulls, Cape genets, mongooses, caracals and domestic cats and dogs may prey on the penguins and their chicks. Mortality from terrestrial predators is higher if penguins are forced to breed in the open in the absence of suitable burrows or nest boxes.

Conservazione

Tendenza della popolazione

declining