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Lecture 13

BIOL 2060 Lecture Notes - Lecture 13: Sea Urchin, Herbivore, Human Hunting

Course Code
BIOL 2060

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Lecture 13: Predation part II
Field studies of predations are more accurate than lab studies
- Examples of study types:
oRemoval of predators
oIntroduction of predators
- Determine if predators have direct or indirect effect
oDirect: predators effect on the prey they are exploiting/preying on
oIndirect: one prey species experiences increased predation due to
increased predator abundance when another prey species increases in
- Exclusion or inclusion experiments
Cage or fences
Removal or control of predators
Introduction of predators
Manipulate presence or density of predators
- Mesocosm and microscom experiments
oSmall scale versions of natural environments used to study
Ex. Aquatic environment simulated in a pool – keep it as
constant with nature as possible
- Predator removal
oTry to determine which predator has the greatest impact by removing
one predator and keeping other present
Ex. duck populations in prairies
Egg predation by skunks – removing skunks improves
nesting success
Repeat experiment with other egg predator species to
determine if skunks have greatest impact
Interactions between predators
- Ex. duck populations in prairies
oRed fox is the dominant egg predator
oCoyotes preys on eggs as well but less than fox
But, fox abundance is depressed by territorial coyotes
Presence of coyotes keeps foxes at bay – has an indirect
positive effect on duck egg hatching success
oFoxes removed: hatching success increased by
oCoyotes removed: hatching success only
increased by 17%
Can conclude that foxes have the greatest
impact on egg predation
Predator-prey coexistence
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