Ornithology

Black-footed penguin

Content Cover Image

African penguins (By Charlesjsharp (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons)

Also known as the 'African Penguin' or 'Cape Penguin', and 'Jackass Penguin', the Black-footed penguin (scientific name: Spheniscus demersus) is one of seventeen species of flightless birds in the family of penguins (Spheniscidae). It is one of four co-called "Banded Penguins" in the genus Spheniscus, which also includes the Humboldt, Magellanic and Galapagos penguins.

 

caption Source Silvie Hojná, Petr Bašus/BioLib/Encyclopedia of Life

 

Conservation Status

 

Scientific Classification

Kingdom: Animalia (Animals)
Phylum:--- Chordata
Class:------ Aves (Birds)
Order:-------- Sphenisciformes
Family:-------- Spheniscidae (Penguins)
Genus:--------- Spheniscus (Banded Penguins)
Species:-------- Spheniscus demersus (Linnaeus, 1758)

Like all penguins, the Black-footed penguin is characterized by its erect posture, torpedo-shaped body, webbed feet, stiff wings (flippers) and an excellent swimming ability, but an awkward movement on land. In common with many other seabirds, penguins possess a counter shading pattern of dark back and white undersides.  This counter shading coloration of dark above and white below makes these seabirds difficult to see from above, the black back blending with the dark sea, while the pale undersides make the birds difficult to see against the sky from below. 

Description

The Black-footed penguin is a medium-sized penguin, about 70 cm (27.6") in height (with males on average being slightly larger than the females), and the only penguin species breeding on the African continent. As with the other members of the genus, there is a dark horseshoe mark on the chest, extending down the sides towards the feet, as well as a speckling of black spots over the white underparts, the number and pattern of which are unique to each bird and are used for identification of individuals.  Occasionally there is a narrow, throat band.  The face is predominantly black, bordered by white on the eyebrows and around the edge of the cheeks.  There is a patch of bare pink skin above each eye and bill, which, along with panting, is thought to aid the bird in losing heat when it is out of the water for prolonged periods.  The chunky bill is black with a paler vertical band towards the tip, while the feet are primarily black. The eyes are hazel. 
Hatchlings are covered in a layer of gray fluffy down, which molts to a bluish-gray second down.  Juvenile plumage is sooty black on the back and around the face, whilst the belly is white.  It takes two or three years for the birds to develop the characteristic adult black-and-white plumage and the striking facial pattern.   These penguins are also known as 'jackass penguins' due to the loud, braying calls that they make on the breeding grounds.

Reproduction

Breeding can occur at any time of year, but varies with location and occurs more frequently from May to July in South Africa and in November to January in Namibia. Breeding sites are on 24 islands between Namibia and Port Elizabeth, South Africa and at three mainland beach sites.

In the Black-footed Penguin, females become sexually mature at about three years of age and males at about four years.  These penguins are usually monogamous. About 80 to 90% of pairs remain together in consecutive breeding seasons, and some are known to have remained together for over 10 years.  During courtship and when pair-bonding, they bray and flap their wings in unison, moving their heads back and forwards as they call, often pointing at the ground.

Black-footed penguins form loose colonies, with pairs returning to the same site year after year. Nests are built in burrows or depressions under boulders and bushes, where they will receive some protection from the sun, and thus avoid the harshest of temperatures. Where there is not much vegetation, they will make their nests in hardened guano.

Black-footed penguins lay two or three eggs at a time, and occasionally second broods have been recorded. Both parents share in the incubation of the eggs, with shifts of one to two days.  Penguins have a bare patch of skin on the lower abdomen (known as the 'brood patch'), which allows greater transfer of heat to the eggs. Incubation lasts for a period of about 40 days.

Once the eggs have hatched, the adults continue to guard the chicks until they are about 30 days old, regurgitating food straight from their stomachs after returning from foraging trips.

Unlike other penguin species, the Black-footed Penguin does not have a strict crèche stage because of the isolative behavior during mating and nesting of the species.  Chicks that are left alone often gather together forming a crèche of up to five birds for general protection. Adults continue to feed their offspring until the chicks fledge, which occurs when the birds reach 70-80 days old.

caption Source: A. Pingstone

At this time the chicks (now immature birds) leave land and remain at sea for 12-24 months. Then they usually return to the land site where they hatched and molt into the familiar black and white plumage of adults.

Only about 40% reach maturity.

Longevity

The life span of a black-footed Penguin in the wild is about 10-11 years of age.  However, some individuals have been known to live as long as 24 years, for instance in collections (e.g. zoos, aquaria): in an environment where protection is given against the elements, disease and predators, animals tend to have longer lifespans, although this doesn't exclude the possibility of the occasional wild individual living to such an age.

Behavior

Adapted for their aquatic lifestyle, Black-footed penguins have been recorded swimming at speeds of 7.4 kilometers per hour (4.6 mi/hr) underwater and can travel a distance of about 30 kilometers (18.6 miles) in a single trip, although the average range covered is about 18 km;  average dives last for 2.5 minutes, and can reach depths of 130 m (426.5 feet).

Black-footed Penguins are very efficient navigators. After months at sea they can find their way back to their original nesting site. Three Black-footed Penguins that were fitted with tracking devices and experimentally relocated to another area, swam 1,287 km (800 miles) back to their breeding site in just one month.

Penguins have waterproof coats that need to be constantly maintained through preening, when they use their bill to apply an oily substance secreted from the uropygial gland, at the base of the tail. Molt occurs yearly to maintin the condition of this coat, at which time these birds come ashore, taking about 20 days to replace their feathers: during this period, they are unable to feed.

caption Black-footed Penguin. Source: Wayne/Encyclopedia of Life

When foraging at sea, the adults live either singly or in small groups of up to 15 birds, most groups consisting of less than five birds.When foraging, breeding birds range about 20km (12.4 miles) from their breeding island, with those with chicks being found within 18km (11.2 miles) of the breeding grounds.  Non-breeding birds forage wider, most occurring within 40km (24.9 miles), but some individuals can be found as far as 90km (55.9 miles) from the nesting grounds.

Although usually silent at sea, individuals will communicate with each other through a series of honks or growls, particularly in fog or at night.. The common name "Jackass Penguin" comes from the loud braying call that the birds make on the breeding grounds.

Although appearing clumsy when walking on land, it is in the sea that these birds show themselves to be the masters of their environment, being very skillful swimmers. African Penguins swim an average of 7.7 km per hour underwater (4.4 mi/hr), but only 1.5 km per hour (0.9 mi/hr) at the surface, an average traveling speed of about 5km per hour (3.1 mi/hr).  As with all penguins, these birds swim by using their feet as rudders and their wings as flippers, although they do paddle with their feet when swimming at the surface. Diving, they streamline their body by drawing the head into their shoulders and tucking their feet up under the body. When diving, these penguins can stay under water for two to three minutes. At the surface, they may also porpoise, a movement involving plunging in and out of the water which allows for a faster, more energy-efficient means of travel than normal swimming, and may enable the animals to breath without any reduction in their travel speed: alternatively, porpoising has been suggested as a means of escaping predators, or purely as an act of exuberance.  The reality is more likely to be a combination of these factors.

In South Africa, the annual molt takes place between November and January whilst on the coasts of Namibia this occurs through April and May.  In preparation for this period of fasting, the penguins increase their food intake from ounces of food daily to pounds, putting on about 30% more fat deposits. The entire molt period takes about 20 days with feather shedding lasting about 13 days of the 20 - during this time, the feathers lack the insulating power of the normal coat, forcing the birds to remain out of the water, and therefore preventing them from foraging.  During this time, the birds can lose up to half their body weight during the molt.  It then takes the penguins about six weeks to regain their condition.

Adaptation

The fossil record shows that penguins are ancient birds, with forms already present in the early Paleocene, inferring that they originated during the Cretaceous, although no penguin fossils of that age are known to exist. As a group, the modern penguins have  become adapted to living in cold water and on cold land.  However, like a few other members of the group, African penguins have a different problem - living in a subtropical climate where the land is warm but where a cold current keeps the ocean water at 5-20o C (41-68o F), African Penguins have had to evolve ways to both survive in cold water and in the heat of the sun.  Whilst their feathers are waterproofed and they possess an insulating layer of subcutaneous fat to fend off the cold of the water, on land they must resort to panting, raising their feathers and holding their wings away from their body to release heat.  In addition, the bare patches of skin (such as that over the eyes) act as heat conductors, allowing excess heat to escape.

Distribution

caption Black-footed Penguin. Source: Wayne/Encyclopedia of Life

The Black-footed penguin is found mostly within 20 kilometers (12.4 miles) of the coast of South Africa emerging onto rocky offshore islands to breed, rest and molt.

The species breeds on 24 offshore islands between Namibia and Port Elizabeth, South Africa. On the mainland, there are colonies of penguins at Betty's Bay and Simonstown, South Africa, and in Namibia. The nesting islands are either flat and sandy with sparse to abundant vegetation or rocky with almost no vegetation. Their mainland sites are beaches with trees and shrubs and are very close to human habitation.

These birds live in inshore coastal waters in the warmer latitudes between 20 and 40o South, where the temperature is 5-20o C (41-68o F). This is not the only penguin species that lives in warmer climates. There are a few other species that live in similar environments on the coasts of Australia and New Zealand, South America, and the Galapagos Islands.

Food Habits

Forty-two percent of the diet of the black-footed penguin is small shoaling fish, with 25 species of fish, including anchovies (Engraulis capensis) and sardines (Sardinops sagax) being recorded, as well as 18 species of crustaceans, three species of squid, and one species of polychaete worm. 

The birds eat about 14% of their body weight each day, i.e. 280-518 g (10.3-18.0 oz). Before molting and when feeding chicks, they may eat over 1000 g/day (2.2 lb). Birds have been recorded as swimming as far as 30-70 km from the coast (18.6-43.5 mi) to forage.

Conservation

The population of Black-footed Penguins has collapsed from several million in the 19th century to 1.2 million in 1930, with only an estimated 120,000 birds left in the wild today, with the population still on the decline.

The collapse is due primarily to human activities such as the former collection of eggs for human consumption (now prohibited); overfishing of sardines and anchovies (preferred food of the penguins); pollution from oil tankers as they round the Cape of Good Hope; removal of guano for fertilizer (now also forbidden) from the islands where the birds built their nesting burrows; predation by feral cats and various other predators, native and introduced, on the islands and mainland. The population is also affected by avian malaria, carried by certain mosquitoes and by human development near their mainland breeding sites.

The species is protected under the agreement of the Conservation of African-Eurasian Migratory Waterfowl. On November 28, 2006, the Center for Biological Diversity, a US organization, filed a petition requesting that twelve species of Penguins, including the Black-footed Penguin, be listed under the US Endangered Species Act. Twenty-three of the twenty-four islands on which the species breeds are listed by the government of South Africa as nature reserves, while the mainland nesting sites are under the protection of South Africa's West Coast National Park Service. Egg collecting and slaughter of birds is now prohibited, while the collection of guano is no longer permitted.

The Black-footed Penguin is classified as Vulnerable (VU) on the IUCN Red List 2007.

It is protected by its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES), and on Appendix II of the Convention on Migratory Species (CMS).  Populations need further monitoring and the possibility of conserving fish stocks is under investigation, amongst other measures, if the future of Africa's only breeding penguin is to be secured.  Today there is an international breeding program among collections to ensure the survival of African Penguins in the event of a catastrophic event in their native habitat.

The recovery of rescued oiled birds has also been shown to be successful.for example, in June 2000, a bulk oil carrier sank off Robben Island near Cape Town releasing thousands of gallons of crude oil. This occurred at the peak of the breeding season of the Black-footed Penguins nesting on the island. Over 18,000 birds became oiled.  An international force of volunteers descended on Cape Town to rescue the affected birds.  Among them was a volunteer sent by the Aquarium of the Pacific who had previous experience treating oiled penguins. Nineteen thousand other birds that were not affected were trucked 1,287 km (800 mi) to Port Elizabeth in order to avoid further catastrophe. Most of the relocated birds found their way back to the island. The effort resulted in the survival of 91% of the birds. 

Uses

Penguins were a good source of guano. Guano was excavated from the shores, processed, and made into fertilizer, which was then sold around the world. Penguin skins have been used as gloves and other leather goods.

There are no real negative economic effects of the Black-footed Penguin. Some fisherman claim that these penguins compete with them for fish, but because of the small size of the animal and the relatively small populations remaining, they consume only around 2,900 tons of fish yearly. This number is too small to be detrimental to that industry.

Further Reading

  1. Spheniscus demersus (Linnaeus, 1758) Encyclopedia of Life (accessed March 16, 2009)
  2. [www.catalogueoflife.org/annual-checklist/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.
  3. Spheniscus demersus, Fichtner, D. 1999, Animal Diversity Web (accessed March 16, 2009)
  4. Spheniscus demersus (Linnaeus, 1758), World Registry of Marine Species (accessed March 16, 2009)
  5. International Penguin Conservation (accessed March 16, 2009)
  6. IUCN Red List (September, 2007)
  7. BirdLife International (accessed March 16, 2009)
  8. CITES (April, 2003) 
  9. ARKive
  10. Global Register of Migratory Species (March, 2008]
Glossary

Citation

Life, E. (2014). Black-footed penguin. Retrieved from http://www.eoearth.org/view/article/51cbed1c7896bb431f68fc57

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