The Wolves and Moose on Isle Royal

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The Wolves and Moose on Isle Royal
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Isle Royale images from http//www.kgcphoto.com/i
sle_royale_national_park.htm
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Wolf and moose images from http//blog.kingsoutdoo
rworld.com/2007/02/
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alright back to work
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• Largest island in lake Superior
• Isolated from mainland most of the time
• Home to moose and wolves
• For now
• concentrate on actions between wolves and moose
  herd
• ignore other influences on moose population (such
  as ?)
• rather limited systems approach
• (see additional reading on web page)

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How to describe feedback
size of moose herd
size of wolf pack
more food on four legs
positive feedback
size of wolf pack
size of moose herd
more hungry mouths to feed
negative feedback
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Example of a Feedback Loop
Size of moose herd
More food for wolves
Appetite for moose
Size of wolf pack
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• Note
• A feedback loop needs to be closed !
• Therefore it needs at least
• two components
• two connections between these components

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Or Somewhat Simplified
positive
size of moose herd
size of wolf pack
negative
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How to analyze a feedback loop

• Need to disturb the system
• Doesnt matter where you start
• Analyze how disturbance moves through the system
• How does wolf moose system behave ?

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Sign of Feedback Loop

• number of negative couplings determines sign of
  feedback loop
• even number of negative couplings positive
  feedback loop
• odd number of negative couplings negative
  feedback loop

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Effects of Negative of Positive Feedbacks
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Effects of Negative of Positive Feedbacks

• positive feedback input signal will be
  amplified
• negative feedback input signal will be damped

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Size of wolf and deer herds
From Science Times (3/19/1996) (http//www.admin.m
tu.edu/urel/PressReleases/feature/wolves/wolf.html
)