# Rabbits, Grass and Weeds

**Compressed source code**: Rabbits, Grass and Weeds**Seminar presentation**: Presentation (in Portuguese-Brasil)**TerraME version**: 2.0 RC-8

## WHAT IS IT?

This model explores a simple ecosystem made of rabbits, grasses and weeds. It was created by Wilensky originally in 2001 using the NetLogo tool.

Its use allows to identify the behavior of a population of herbivores in relation to their environment.

## HOW IT WORKS

Rabbits roam randomly through space, and grass and weeds randomly grow in space.

Cells in the cellularspace are classified as soil, grass and grass. In which grams provide more energy to rabbits than weeds.

The cell space is set to start completely with soil and go “popping” grass and weeds in the soil over time.

At each timestep, the amount of growth of grasses and herbs is created in the cell space, with a probability of 1/9 growth (by default).

At each timestep the rabbits move in space it loses 0.5 energy, when it reaches the birth-threshold energy it reproduce, when it reaches 0, it dies.

In this implementation, some increments besides the NetLogo model were proposed so that the user can reach his own conclusions.

One difference is that now the user can perform an experiment on how the model behaves with the rabbit choosing the cell of its neighbors that gives more energy.

Another differential is the possibility of the user performing an experiment having competitive environments between grams and herbs. At which they will have a higher growth rate based on the neighborhood of the cell chosen for growth.

## HOW TO USE IT

Before executing the model, the user must define the following parameters (Parameters in parenthesis are considered standard):

Initial amount of rabbits - RABBITS_POPULATION (50)

Amount of energy a rabbit must have to reproduce - BIRTH_THRESHOLD (15)

Grass growth rate GRASS_GROW_RATE (100)

Weed growth rate - WEEDS_GROW_RATE (100)

Amount of energy supplied when eating grass - GRASS_ENERGY (10)

Amount of energy supplied when eating weed - WEED_ENERGY (5)

Cellular Space Size - CELLSPACESIZE (40)

Choice of movement type - MovementChoice (0)

This parameter can assume the value of 0 or 1. 0: for random movements of the rabbits in space. 1: for drives by randomly choosing the neighbor that gives the highest power gain to the rabbit.

DominanceChoice (0)

Every plant has a 1/9 chance of not growing when it is not competitive. If it is competitive, it will have the probability: (number of neighbors equal + 1) / 9. This implies that if all neighbors are equal to it, it will be 100% likely to be born.

This parameter can assume the value of 0, 1, 2, 3. 0: Both non-competitive 1: Competitive grass 2: Competitive grass 3: Both competitive

## THINGS TO NOTICE

This section could give some ideas of things for the user to notice while running the model (e. g. model analysis, evaluation, charts, maps, screenshots, etc).

## THINGS TO TRY

Try to answer these questions with the model:

- What happens to the rabbit population if herbs and grasses have the same growth?

- If starting with more rabbits, the average amount over time will also be higher?

- What happens if the birth rate is high?

- What happens if the mortality rate is high?

- What happens if there is more grass growth than grass?

- What happens if there are more grams than herbs?

- What happens to the rabbit population if they decide to always feed by choosing to move to the space that gives more energy?

You can get the answers to the questions by varying the parameters!

## EXTENDING THE MODEL

You can try to make more adaptations to the model to answer more questions not yet raised.

You can also try to join the maps of the ground with the one of rabbits.

## TerraME FEATURES

An implementation in the rabbit move rule in the forEachNeighbor function was required to select a random neighborhood feature. The sample function always returns the same order of neighbors, so it would create a computational artifact in the response.

## RELATED MODELS

NetLogo: (Original Rabbits, Grass and Weeds) TerraME: (Prey-Predactor)

## CREDITS AND REFERENCES

Book: Argument-driven Inquiry in Biology: Lab Investigations for Grades 9-12. https://books.google.com.br/books?id=jONrBgAAQBAJ&lpg=PA132&dq=rabbits%20grass%20weeds&hl=pt-BR&pg=PP1#v=onepage&q=rabbits%20grass% 20weeds&f=false

NetLogo Model: Wilensky, U. (2001). NetLogo Rabbits Grass Weeds model. http://ccl.northwestern.edu/netlogo/models/RabbitsGrassWeeds. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

NetLogo Program: Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

TerraME: http://www.terrame.org/

Modelo de referência Prey-Predactor: TerraME Prey-Predactor: http://www.terrame.org/packages/doc/base/doc/files/examples.html#predator-prey