Wolf Moose Predation

globals [ max-moose ]  ; don't let moose population grow too large
; moose and wolves are both breeds of turtle.
breed [ moose a-moose ]  ; moose is its own plural, so we use "a-moose" as the singular.
breed [ wolves wolf ]
breed [ plants plant ]
turtles-own [ energy ]       ; both wolves and moose have energy
patches-own [ countdown ]

to setup
  clear-all
  set max-moose 10000

  ask patches [
    set pcolor green + 3
    set countdown random plant-regrowth-time  ; initialize plant regrowth times randomly
  ]
  ask n-of ( count patches / 2 ) patches [
    sprout-plants 1 [
      set shape "plant"
      set color green - 2
    ]
    set countdown plant-regrowth-time  ; overwrite random regrowth time if there is a plant present
  ]

  create-moose initial-number-moose  ; create the moose, then initialize their variables
  [
    set shape "moose"
    set size 2  ; easier to see
    set label-color blue - 2
    set energy random (2 * moose-gain-from-food)
    setxy random-xcor random-ycor
  ]

  create-wolves initial-number-wolves  ; create the wolves, then initialize their variables
  [
    set shape "wolf"
    set color black
    set size 2  ; easier to see
    set energy random (2 * wolf-gain-from-food)
    setxy random-xcor random-ycor
  ]

  reset-ticks
end 

to go
  ; stop the simulation of no wolves or moose
  if not any? turtles [ stop ]
  ; stop the model if there are no wolves and the number of moose gets very large
  if not any? wolves and count moose > max-moose [
    user-message "The moose have inherited the earth"
    stop
  ]
  ; stop the model after 500 ticks
  if ticks >= 500 [ stop ]

  ask moose [
    move
    set energy energy - 1
    eat-plant
    maybe-die
    reproduce-moose  ; moose reproduce at rate governed by slider
  ]

  ask wolves [
    move
    set energy energy - 1  ; wolves lose energy as they move
    eat-moose ; wolves eat a moose on their patch
    maybe-die
    reproduce-wolves ; wolves reproduce at random rate governed by slider
  ]

  ask patches [ grow-plant ]

  tick
end 

to move  ; turtle procedure
  rt random 50
  lt random 50
  fd 1
end 

to eat-plant  ; moose procedure
  ; moose eats plant, plant dies
  let food one-of plants-here
  if food != nobody [
    ask food [
      die
    ]
    set energy energy + moose-gain-from-food  ; moose gain energy by eating
  ]
end 

to reproduce-moose  ; moose procedure
  if random-float 100 < moose-reproduce [  ; throw "dice" to see if you will reproduce
    set energy (energy / 2)                ; divide energy between parent and offspring
    hatch 1 [ rt random-float 360 fd 1 ]   ; hatch an offspring and move it forward 1 step
  ]
end 

to reproduce-wolves  ; wolf procedure
  if random-float 100 < wolf-reproduce [  ; throw "dice" to see if you will reproduce
    set energy (energy / 2)               ; divide energy between parent and offspring
    hatch 1 [ rt random-float 360 fd 1 ]  ; hatch an offspring and move it forward 1 step
  ]
end 

to eat-moose  ; wolf procedure
  let prey one-of moose-here                    ; grab a random moose
  if prey != nobody  [                          ; did we get one?  if so,
    ask prey [ die ]                            ; kill it, and...
    set energy energy + wolf-gain-from-food     ; get energy from eating
  ]
end 

to maybe-die
  if energy < 0 [ die ]
end 

to grow-plant  ; patch procedure
  ; countdown on brown patches: if reach 0, grow some plant
  if not any? plants-here [
    ifelse countdown <= 0
    [
      sprout-plants 1 [
        set shape "plant"
        set color green - 2
      ]
      set countdown plant-regrowth-time
    ] [
      set countdown countdown - 1
    ]
  ]
end 

; Copyright 1997 Uri Wilensky.
; See Info tab for full copyright and license.