NetLogo User Community Models
Wolf-Sheep Predator-Mediated Coexistence (FINAL)
by Teresa S. Alexandre, Vanessa Costa & Rúben Rego (Submitted: 09/03/2017)
## WHAT IS IT?
This model explores the predator-mediated coexistence, which occurs when selective predation favours the coexistence of prey species that might otherwise exclude one another, contributing to an increase of the number of species in a community as long as the preferred prey species is the competitively dominant.
## HOW IT WORKS
There are two types of prey: sheep and goats. The competition between them can be changed in the interface.
## HOW TO USE IT
1. Set the GRASS? switch to TRUE to include grass in the model, or to FALSE to only include wolves (red) and sheep (white).
## THINGS TO NOTICE
Notice that when there's no wolves in the ecosystem, the dynamics between populations of goats and sheep will change. How so? Why does that happen?
## THINGS TO TRY
Try adjusting the parameters under various settings. How sensitive is the stability of the model to the particular parameters?
Try to change the wolf-goat-preference in the interface. How does that afect the populations?
Try to change the competitive dominace between goats and sheep by playing with the 'sheep-gain-from-food' or'sheep-reproduce' and the 'goat-gain-from-food' or 'goat-reproduce'. How does that affect the populations?
Take wolfs out of the equations changing the 'initial-number-wolves' to 0. What will happen?
## EXTENDING THE MODEL
There are a number ways to alter the model so that it will be stable with only wolves and sheep (no grass). Some will require new elements to be coded in or existing behaviors to be changed. Can you develop such a version?
Can you modify the model so the sheep will flock?
Can you modify the model so that wolf actively chase sheep?
## RELATED MODELS
* Wilensky, U. (1997). NetLogo Wolf Sheep Predation model. http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
## CREDITS AND REFERENCES
Townsend, C. R., Begon, M. & Harper, J. L. (2008). Essentials of Ecology. Third Edition. Blackwell Publishing, 522 pp.
## HOW TO CITE
If you mention this model or the NetLogo software in a publication, we ask that you include the citations below.
For the model itself:
* Alexandre, T. S., Costa, V. & Rego, R. (2017) NetLogo Wolf-Sheep Predator-Mediated Coexistence model. Model built under the orientation of Doctor José M. N. Azevedo. Biology Department, University of Azores, Ponta Delgada.
Please cite the NetLogo software as:
* Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
## COPYRIGHT AND LICENSE
Copyright 2017. Teresa Sofia Alexandre, Vanessa Costa e Rúben Rego.
![CC BY-NC-SA 3.0](http://ccl.northwestern.edu/images/creativecommons/byncsa.png)
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