Published on January 1, 2008
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.