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Extinction and Endangerment

Extinction and Endangerment. Extinction Case Histories Extinction Causes Introduction to Endangerment of Species. Extinction case histories. Dodo Heath hen North American burying beetle Hawaiian fauna Passenger Pigeon. The Dodo ( Raphus cuculatus ).

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Extinction and Endangerment

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  1. Extinction and Endangerment Extinction Case Histories Extinction Causes Introduction to Endangerment of Species

  2. Extinction case histories • Dodo • Heath hen • North American burying beetle • Hawaiian fauna • Passenger Pigeon

  3. The Dodo (Raphus cuculatus) • First known to Western science, Mauritius in 1598 • Extinct by 1681 • Biology • ate fruit • large (100 lbs.) • Causes of extinction • exploitation by sailors for food • habitat destruction of forest/food supply • introduced predators--rats, monkeys, pigs • What did it look like?

  4. Hawaiian fauna • Overview from Bishop museum • Examples: • Black mamo • Green silversword • Causes • habitat destruction • competition from exotic species • introduction of exotic diseases and predators

  5. THE HEATH HEN • Lived in Coastal Marshes along the Atlantic and numbered in 10s - 100,000s • Hunting pressure from European settlers . • Marshes turned to agriculture • fire in habitat • invasion of northern native predators during a low snowshoe hare year • 1900 100 individuals • 1907 created refugia, protected habitat, removed predators • 1916 population increased to 800. • fire wiped through island causing decrease in population • Winter 1916/17 10 year low in snowshoe hare caused invasion of goshawks and snowy owls, increasing predation. • 1917 100 animals • 1920 200 animals • 1921 diseased chickens brought to island spread to hens reduced population to 100 animals. • 1922-32 many infertile eggs (inbreeding depression, etc.) • change in sex ratio (10 males/female) • 1932 EXTINCT

  6. Causes of extinction • Ecological • Ultimate • Proximate • Human influences • overexploitation • Habitat destruction • Introductions and exterminations • Pollution • Ecosystem cascades • Mismanagement and or confusion

  7. Ultimate Ecological Causes of Extinctions • Population abundance naturally low • Geographic range small • Patchy distributions within overall range • Body size large • Top predators (high trophic position) • Highly specialized • habitats • breeding sites • food • migratory species

  8. Proximate Ecological Causes of Extinctions • Demographic stochasticity • Environmental stochasticity • Genetic failure • Natural catastrophes

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