NetLogo Models Library:
IABM Textbook/chapter 4

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Wolf Sheep Simple 4

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 fourth model in a set of five models that build towards a predator prey model of population dynamics. This fourth model gives the sheep the ability to reproduce.

HOW IT WORKS

The model creates a population of sheep that wander around the landscape. Moving around costs some energy, and when their energy gets too low, sheep die. However, the sheep can eat grass in the environment to regain energy and the grass regrows over time. If the energy of a sheep gets above a certain level, it can reproduce.

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.

After this, press the GO button to make the sheep move around the landscape, and eat the grass.

THINGS TO NOTICE

Is there any relationship between where the sheep die off and where they reproduce?

Do all the sheep reproduce at the same time? Why is that?

THINGS TO TRY

How does reproduction affect the model results? Is it easier to get the sheep to continue to live? For instance, do the values of GRASS-REGROWTH-RATE, MOVEMENT-COST and ENERGY-GAIN-FROM-GRASS necessary to balance the sheep population change when the sheep reproduce?

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 4 model. http://ccl.northwestern.edu/netlogo/models/WolfSheepSimple4. 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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