1. The average lifespan of penguins is probably 15 to 20 years. Some individuals live considerably longer (Sparks and Soper, 1987).
2. High mortality occurs among the young.
a. Winter starvation may claim the lives of 50% of king chicks (Cherel, et al., 1987; Davis and Darby, 1990).
b. Emperor chicks may experience a 90% mortality within the first year of life (Sparks and Soper, 1987).
c. When mortality affects one chick in species producing two offspring of moderate size differences, it is usually the smaller chick that does not survive (Davis and Darby, 1990).
1. When in the water, penguins may be eaten by leopard seals, fur seals, sea lions, sharks, or killer whales (Sparks and Soper, 1987; Simpson, 1976).
2. On land, foxes, snakes, and introduced predators such as feral dogs, cats, and stoats (members of the weasel family) prey on eggs and chicks of some penguin species, including the yellow-eyed and Galapagos penguins (Sparks and Soper, 1987; Muller-Schwarze, 1984).
3. Antarctic and subantarctic eggs and chicks are susceptible to predatory birds such as antarctic skuas, sheathbills, and giant petrels (del Hoyo, et al., 1992). These predators may prey on chicks that have strayed from the protection of the creche or are sickly and too weak to defend themselves (Simpson, 1976; Sparks and Soper, 1987).
a. Skuas may work in pairs to obtain their prey. One bird distracts the penguin on the nest, and the other swoops in to steal the egg or chick (Sparks and Soper, 1987).
b. Sheathbills intercept chinstrap regurgitation as penguin parents feed their offspring (Sparks and Soper, 1987).
4. Gulls and ibises eat 40% of African penguin eggs (Sparks and Soper, 1987).
5. Fairy penguins rely on burrows and a nocturnal lifestyle to avoid predators such as swamp harriers, peregrines, gulls, snakes, rats, and lizards (Peterson, 1979; Sparks and Soper, 1987).
The leopard seal is a predator of penguins.
C. Human Impact
1 . Historians believe that indigenous peoples have hunted some species of penguins and taken eggs for centuries (Sparks and Soper, 1987).
2. Mass exploitation occurred when early explorers, sealers, whalers, and fishermen turned to penguin colonies as sources of fresh meat and eggs (Moller-Schwarze, 1984). Sometimes more than 300,000 eggs were taken in annual harvests from one African island (Sparks and Soper, 1987). Explorers were known to kill and salt 3,000 penguins in a day for voyage provisions (Simpson, 1976). Penguins were easy prey because of their inability to fly and their seeming lack of fear of humans (Sparks and Soper, 1987). Although egg-collecting was banned in 1969, illegal harvesting continues today (del Hoyo, et al., 1992).
3. During much of the 19th century, and into the 20th, penguin skins were used to make caps, slippers, and purses. Feathers were used for clothing decorations and as mattress stuffing (del Hoyo, et al., 1992; Simpson, 1976; Sparks and Soper, 1987). Inhabitants of the remote island grouping in the South Atlantic, Tristan da Cunha, still depend on penguins for eggs, feathers, oil, and skins (Simpson, 1976).
4. The extraction of oil from penguins' fat layers became economically important in the 1800s and early 1900s. Oil was used for lighting, tanning leather, and fuel. In the Falkland Islands alone, an estimated 2.5 million penguins were killed within a 16-year timespan. The oil industry came to a halt in 1918 due to protests by the general public and because of cheaper and better quality chemical products (del Hoyo, et al., 1992; Sparks and Soper, 1987).
5. Humboldt penguin guano has great commercial value as a nitrogen-rich fertilizer. Although the Incas used penguin and seabird guano to improve their crops as far back as 500 B.C., they carefully managed the resource by extracting it at a slower rate than it was being produced. Guano became a major product of international trade in the 1800s, and in the early 1900s the deposits were in danger of being depleted (Sparks and Soper, 1987). Guano harvesting is better managed today, but overexploitation of this commodity is a serious threat to the Humboldt population (Araya and Todd, 1988).
6. In some places, such as islands in the southern Indian Ocean, fishermen still use penguin meat for bait (del Hoyo, et al., 1992).
7. Human competition for food sources can affect penguin populations. Overfishing of anchovetta (a small fish), the primary food source of the Humboldt penguin, has contributed to their population decline (Araya and Todd, 1988).
8. The introduction of predators has had devastating effects in some areas. Rats, dogs, pigs, and ferrets have been known to prey on chicks, eggs, and even adult penguins. Introduced herbivores, such as sheep and rabbits, cause serious deterioration of habitat (del Hoyo, et al., 1992).
9. Colonies of penguins have been affected by building activities and road construction. One colony of king penguins at Iles Crozet (a small group of islands in the Indian Ocean) was completely destroyed. A nearby area was cleared, and fortunately, the penguins recolonized (Marchant, 1990).
10. Trash in the ocean can affect seabirds. Penguins have been known to ingest plastic or become tangled in debris, causing injury and death (del Hoyo, et al., 1992).
11. Oil spills affect penguins.
a. Oil fouls their feathers, reducing the waterproofing and insulating properties of their plumage. The birds become susceptible to hypothermia (chilling).
b. Penguins also ingest the oil while trying to preen, poisoning them and causing internal organ damage (del Hoyo, et al., 1992). c. Oil spills are a continued threat (Muller-Schwarze, 1984). In June 1994, an estimated 40,000 African penguins were affected by an oil spill off South Africa's Cape peninsula. More than 2,400 tons of fuel oil was spilled. The disaster occurred during the penguins' breeding season, affecting the survival of chicks and unhatched eggs. The long-term success of emergency clean-up efforts probably will not be determined for several years. (San Diego Union Tribune, 29 June 1994).
12. Traces of dichlorodiphenyltrichloroethane (DDT) and other pesticides (chlorinated hydrocarbons) have been found in the tissues of Adélie and chinstrap penguins. Scientists speculate that these pollutants were transported by ocean currents or other animals. Their appearance in antarctic penguins is significant in that these toxic substances have now reached the pristine Antarctic (del Hoyo, et al., 1992).
Enthusiastic sightseers must be careful not to interfere with normal penguin activity.
13. Activity that may seem harmless, such as aircraft flying over penguin colonies, may cause panic and stampedes, resulting in injuries and easy predation (del Hoyo, et al., 1992).
14. The popularity of "ecotourism" is increasing with cruise ships frequenting antarctic waters. Enthusiastic sightseers must be careful not to interfere with normal penguin activity by staying back and keeping noise levels down (MOller-Schwarze, 1984).
15. Penguins may be indirectly affected by past hunting of whales. The increase of some penguin species over the last 30 years may be attributed to the greater availability of krill following the reduction of some antarctic whale populations (Marchant, 1990). However, the commercial value of krill may encourage large-scale harvesting of this resource in south polar waters, which would impact penguins and other marine animals that rely upon krill as a food source (Sparks and Soper, 1987).
D. El Nino
El Nino is a natural phenomenon that involves a change in wind and ocean current patterns, which warms surface temperatures and reduces the upwelling of nutrient-rich water. A decrease in nutrients affects plankton, krill, and small fishes, which comprise the food supply for marine animals. The penguin species most affected are the Humboldt and Galapagos penguins (del Hoyo, et al., 1992). The 1982 El Nino caused a 65% depletion of the Humboldt population off the coast of Peru (Collar and Andrew, 1988). Up to 77% of the Galipagos population was wiped out, leaving only 463 total birds. A slow recovery began in 1985 (del Hoyo, et al., 1992).
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