Longevity & Causes of Death

Penguin

Longevity & Causes of Death

Longevity

  1. The average life expectancy of penguins is probably 15 to 20 years. Some individuals live considerably longer.
  2. High mortality occurs among the young.
    • Winter starvation may claim the lives of 50% of king penguin chicks.
    • Emperor chicks may experience a 90% mortality within the first year of life.
    • When mortality affects one chick in species producing two offspring of moderate size differences, it is usually the smaller chick that does not survive.

There is a high mortality rate among penguin chicks.

Predators

  1. When in the water, penguins may be eaten by leopard seals, fur seals, sea lions, sharks, or killer whales.
  2. This leopard seal is one of the primary predators of penguins but
    poses more of a threat in the water than on land.

  3. 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 Galápagos penguins.
  4. Antarctic and subantarctic eggs and chicks are susceptible to predatory birds such as antarctic skuas, sheathbills, and giant petrels. These predators may prey on chicks that have strayed from the protection of the crèche or are sickly and too weak to defend themselves.
    • 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.
    • Sheathbills intercept chinstrap regurgitation as penguin parents feed their offspring.
  5. Antarctic skuas (Catharacta antarctica), sheathbills (Chionis alba), and
    giant petrels (Macronectes giganteus) prey on
    penguin eggs and chicks.

  6. Gulls and ibises eat 40% of African penguin eggs.
  7. Fairy penguins rely on burrows and a nocturnal lifestyle to avoid predators such as swamp harriers, peregrines, gulls, snakes, rats, and lizards.

Human Impact

  1. Historians believe that, for centuries, indigenous peoples have hunted some species of penguins and taken eggs.
  2. Mass exploitation occurred when early explorers, sealers, whalers, and fishermen turned to penguin colonies as sources of fresh meat and eggs. Sometimes more than 300,000 eggs were taken in annual harvests from one African island. Explorers were known to kill and salt 3,000 penguins in a day for voyage provisions. Penguins were easy prey because of their inability to fly and their seeming lack of fear of humans. Although egg-collecting was banned in 1969, illegal harvesting continues today.
  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.
  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 time span. 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.
  5. Seabird guano has great commercial value as a nitrogen-rich fertilizer. Although the Incas used seabird guano to improve their crops as far back as 500 BC, 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, Guano deposits were in danger of being depleted. Guano harvesting is better managed today, but overexploitation of this commodity is a serious threat to the Humboldt penguin population, which relies on accumulated seabird guano to dig burrows into rocky and soil-poor nesting areas.
  6. In some places, such as islands in the southern Indian Ocean, fishermen still use penguin meat for bait.
  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 penguin population declines.
  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.
  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.
  10. Trash in the ocean can affect seabirds. Penguins have been known to ingest plastic or become tangled in debris, causing injury and death.
  11. Oil spills affect penguins.
    • Oil fouls penguin feathers, reducing the waterproofing and insulating properties of their plumage. The birds become susceptible to hypothermia (chilling).
    • Penguins also ingest the oil while trying to preen, which poisons them and causes internal organ damage.
    • On June 23, 2000 the ore carrier Treasurer caused an oil spill near Robben and Dassen islands off South Africa. The International Fund for Animal Welfare's (IFAW) International Oiled Wildlife Response Team, directed by the International Bird Rescue Research Center (IBRRC), was immediately mobilized to South Africa to help care for more than 20,000 oiled penguins. Due to this rapid response, within a year, the African penguin population on Robbin Island recovered to prespill numbers. (University of Cape Town Web site)
  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.
  13. Activity that may seem harmless, such as aircraft flying over penguin colonies, may cause panic and stampedes, resulting in injuries and easy predation.
  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.
  15. Ecotourism is bringing more people into the penguins' habitat to
    observe them. However, effort must be made to not interfere with
    normal penguin activity.

  16. 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. 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.

El Niño

  1. The El Niño Southern Oscillation (ENSO) 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 Galápagos penguins.
    • The 1982-1983 ENSO caused a 65% depletion of the Humboldt population off the coast of Peru. The population partially recovered, but once again plummeted during the 1997-1998 El Niño event. (BirdLife International, 2005)
    • Up to 77% of the Galápagos penguin population was wiped out by the 1982-1983 ENSO, leaving only 463 total birds. A slow recovery began in 1985. However, a further decline of 66% of the population occurred during the 1997-1998 ENSO. The population appears to be once again in a recovery phase. (BirdLife International, 2005)