Isle Royale Simulation

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A Predator-Prey Simulation Using Field Data from Isle Royale, Michigan Alan Raetz: 

A Predator-Prey Simulation Using Field Data from Isle Royale, Michigan Alan Raetz

Isle Royale, Michigan: 

Isle Royale, Michigan 544 square kilometers on Lake Superior 44 miles long, 8 miles wide US National Park Wilderness Area ~ 50 years of Predator/Prey Field Data Moose is 90% of wolf diet Very little immigration or emigration

Slide4: 

Isle Royale Wolf Population (Peterson, 1999)

Slide5: 

Isle Royale Moose Population (Peterson, 1999)

Isle Royale: Theoretical Models of Predator/Prey Relationships: 

Isle Royale: Theoretical Models of Predator/Prey Relationships John Vucetich, 2002 paper in Ecology Do spatial relationship predict how often predators kill prey (kill rate)? Prey density Predator density Prey/Predator ratio Simple theoretical models using field data Practical tool for wildlife management?

Computer Simulation: 

Computer Simulation No, it’s not that kind of simulation...

Simulation “Strange World”: 

Simulation “Strange World” Predators and Prey evolve behaviors Survivors pass genetic information to offspring Behavior is not pre-programmed Environment determines behavior Outcome of a simulation is not known Goal: Test predator/prey theories

Questions: 

Questions If the spatial relationships of Isle Royale are duplicated in the simulation, will the outcome also mimic the field data? Is predator and prey density a major factor of predator success in the simulation? How useful is this computer model in predicting actual field data?

Methods: 

Methods What are the assumptions in the model? Based on Isle Royale Field Data 1971-2001 Train predators and prey under average conditions Predator population range: 10 - 52 Wolves Prey population range: 550 - 2500 Moose 100 km2 (6.2 x 6.2 miles) simulation area. 1 pixel on screen = 10 m x 10 m space

Slide12: 

Results

Slide13: 

Isle Royale Field Data Vucetich (2002) - Reduction in kill rate as predator population increases due to reduced prey availability ?

Example: 6 predators, 200 prey: 

Example: 6 predators, 200 prey

Slide16: 

Isle Royale Field Data Vucetich (2002)

Slide18: 

Isle Royale Field Data Vucetich (2002)

Results: 

Results Prey density is the major factor of predator kill rates in the simulation. Field data of Moose/Wolf populations on Isle Royale correlates somewhat. Simulation runs show large variance, but averaged over time, these results show predictable trends (not true of field data).

Conclusion: 

Conclusion Spatial density is only one of many factors in predator success on Isle Royale. Simple simulations can’t predict complex interactions.