NetLogo Models Library:
IABM Textbook/chapter 4

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Wolf Sheep Simple 5

If you download the NetLogo application, this model is included. You can also Try running it in NetLogo Web

ACKNOWLEDGMENT

This model is from Chapter Four of the book "Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo", by Uri Wilensky & William Rand.

• Wilensky, U. & Rand, W. (2015). Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo. Cambridge, MA. MIT Press.

This model is in the IABM Textbook folder of the NetLogo Models Library. The model, as well as any updates to the model, can also be found on the textbook website: http://www.intro-to-abm.com/.

WHAT IS IT?

This is the fifth model in a set of models that build towards a predator prey model of population dynamics. This fifth model adds wolves and completes the predator prey model.

It extends the model Wolf Sheep Simple 4.

HOW IT WORKS

The model creates a population of sheep that wander around the landscape. For each step the sheep take it costs them some energy and if there energy gets too low they die. However, the sheep can eat grass in the environment to regain energy and the grass regrows over time. If the energy of the sheep gets above a certain level then they can reproduce.

In this fifth model, there are also wolves. Wolves have the same behaviors as sheep except for eating; rather than grass, they eat sheep.

HOW TO USE IT

Set the NUMBER-OF-SHEEP slider and press SETUP to create the initial population. You can also change the MOVEMENT-COST slider to affect the energy cost of movement for the sheep. The GRASS-REGROWTH-RATE slider affects how fast the grass grows back, while the ENERGY-GAIN-FROM-GRASS slider affects how much energy the sheep can gain from eating the grass, and the ENERGY-GAIN-FROM-SHEEP slider affects how much energy the wolves gain from eating sheep.

After this, press the GO button to make the sheep and wolves move around the landscape, and interact.

THINGS TO NOTICE

How does the number of sheep affect the population levels? How does the number of wolves affect the population levels?

Is there a spatial relationship between where the sheep do well and where the wolves do well?

How does the presence of wolves affect the system?

THINGS TO TRY

Change the NUMBER-OF-WOLVES, while leaving the NUMBER-OF-SHEEP constant, how does this affect the model results?

How does the ENERGY-GAIN-FROM-SHEEP affect the model results?

Try to play around with ENERGY-GAIN-FROM-GRASS and GRASS-REGROWTH-RATE. Does keeping the influx of energy constant but with different slider valeus (e.g. ENERGY-GAIN-FROM-GRASS as 1 and GRASS-REGROWTH-RATE as 2, and vice versa) give the same or different results? Why might that be?

RELATED MODELS

The Wolf Sheep Predation Model in the Biology section of the NetLogo models library.

CREDITS AND REFERENCES

This model is a simplified version of:

• 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.

HOW TO CITE

This model is part of the textbook, “Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo.”

If you mention this model or the NetLogo software in a publication, we ask that you include the citations below.

For the model itself:

• Wilensky, U. (2007). NetLogo Wolf Sheep Simple 5 model. http://ccl.northwestern.edu/netlogo/models/WolfSheepSimple5. Center for Connected Learning and Computer-Based Modeling, Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL.

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.

Please cite the textbook as:

• Wilensky, U. & Rand, W. (2015). Introduction to Agent-Based Modeling: Modeling Natural, Social and Engineered Complex Systems with NetLogo. Cambridge, MA. MIT Press.

COPYRIGHT AND LICENSE

Copyright 2007 Uri Wilensky.

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.

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