Extinction and Endangerment

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