; "Management Scenarios for the return of Canis Lupus to Lower Saxony "

; 01.03.2019

; Jonas Boersch
; Jannis Classnitz

; Leuphana Universität Lüneburg
; Module: Interdisciplinary Sustainability Studies, Course: Oekosystemmodellierung
; Prof. Dr.-Ing. Eckhard Bollow, Dr. Carsten Lemmen

; @copyright CC BY-NC-SA 4.0

;*******************************************************************************************************************************

; Content:
; 1. Globals and Variables
; 2. Setup Procedure
;  2.1 Setup Patches
;  2.2 Setup Turtles
;  2.3 Setup Calender
; 3. Go Procedure
;  3.1 Advance Calender
;  3.2 Define Forest Procedure
;  3.3 Go Turtles Procedure
;  3.4 Management Procedure
;  3.5 Die Crossing Streets Procedure
; 4. Move Turtle Procedure
; 5. Reproduce Procedure
; 6. Eat and Grow Forest Procedure
; 7. Catch Procedure
;  7.1 Problem Wolves
;  7.2 Wooden Fence
;  7.3 Electric Fence
;  7.4 Shepherd Dog
; 8. Hunt Procedure
;  8.1 Kill Wolves
;  8.2 Protect Fields
;  8.3 Protect Settlements

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 1. Globals and Variables
;*******************************************************************************************************************************

globals

  [ days-in-month                                                                 ; how many days every month has
    year month day                                                                ; set a year, a month and a day
    doy                                                                           ; day of the year is shown
    forest-patches                                                                ; define certain patches as forest
  ]

breed [ boars boar ]                                                              ; the different breeds are: boars,
breed [ deer a-deer ]                                                             ; deer,
breed [ wolves wolf ]                                                             ; wolves,
breed [ livestock a-livestock ]                                                   ; livestock and
breed [ hunters hunter ]                                                          ; hunters

wolves-own [ threat-level ]                                                       ; wolves own a threat level
patches-own [ countdown ]                                                         ; patches own a countdown

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 2. Setup Procedure
;*******************************************************************************************************************************

to setup

  clear-all
  setup-patches
  setup-turtles
  reset-calendar
  reset-ticks
end 

;*******************************************************************************************************************************
; 2.1 Setup Patches
;*******************************************************************************************************************************

to setup-patches

  Import-pcolors "map - Kopie.png"                                                ; import map as patch color
                                                                                  ; scale 1:2.000.000 ( 1 patch = 500 m² )                                                         (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
end 

;*******************************************************************************************************************************
; 2.2 Setup Turtles
;*******************************************************************************************************************************
; Similar to Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017

to setup-turtles

  ask n-of num-boars patches with [ pcolor = 56 ] [ sprout-boars 1 ]              ; patches with specific color sprout the breeds
  ask n-of num-deer patches with [ pcolor = 56 ] [ sprout-deer 1 ]
  ask n-of num-wolves patches with [ pcolor = 56 ] [ sprout-wolves 1 ]
  ask n-of num-livestock patches with [ pcolor = 46.7 ] [ sprout-livestock 1 ]
  ask n-of num-hunters patches with [ pcolor = 46.7 ] [ sprout-hunters 1 ]



  ask boars                                                                       ; the breed of boars shall be created
    [ set shape "wildschwein"
      set color brown
      set size 10
    ]

  ask deer                                                                        ; the breed of deer shall be created
    [ set shape "rotwild"
      set color red
      set size 10
    ]

  ask wolves                                                                      ; the breed of wolves shall be created
    [ set shape "wolf"
      set color black
      set size 10
      set threat-level 1
    ]

  ask livestock                                                                   ; the breed of livestock shall be created
    [ set shape "farmtier (kuh)"
      set color white
      set size 10
    ]

  ask hunters                                                                     ; the breed of hunters shall be created
    [ set shape "jäger"
      set color orange
      set size 20
    ]
end 

;*******************************************************************************************************************************
; 2.3 Setup Calender
;*******************************************************************************************************************************

to reset-calendar                                                                 ; by pressing the set-up button,
                                                                                  ; the calendar shall be reset on
  set year 2019                                                                   ; 01.01.2019
  set doy 1
  set day doy
  set month 1
  set days-in-month ( list 31 28 31 30 31 30 31 31 30 31 30 31 )
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 3. Go Procedure
;*******************************************************************************************************************************
;Similar to Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017

to go

  tick
  advance-calender
  define-forest
  if not any? turtles [ stop ]

  ask boars [ go-boars ]
  ask deer [ go-deer ]
  ask wolves [ go-wolves ]
  ask livestock [ go-livestock ]
  ask hunters [ go-hunters ]
  ask patches [ grow-forest ]
end 

;*******************************************************************************************************************************
; 3.1 Advance Calender
;*******************************************************************************************************************************

to advance-calender

  set day day + 1                                                                 ; Update the day monitors
  set doy doy + 1                                                                 ; based on the day of year

  let my-doy sum sublist days-in-month 0 month + 1                                ; sum up the days of the months already passed

  if doy > my-doy - 1                                                             ; jump to the next month and reset the day
    [ set month month + 1
      set day 1
    ]

  if doy > 59 [ set my-doy my-doy + leap-year ]                                   ; in leap years add 1
                                                                                  ; (2020 is the next leap year)
  if doy > 365 + leap-year                                                        ; jump to the next year and reset the day
    [ set year year + 1
      set month 1
      set doy 1
      set day 1
    ]
end 

to-report leap-year

  if (( year mod 4 ) != 0 )  [ report 0 ]
  if (( year mod 400 ) = 0 ) [ report 1 ]
  if (( year mod 100 ) != 0 ) [ report 0 ]
  report 1
end 

;*******************************************************************************************************************************
; 3.2 Define Forest Procedure
;*******************************************************************************************************************************

to define-forest

  set forest-patches patches with [ shade-of? green pcolor ]                      ; the forest patches shall be those with green color              (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
end 

;*******************************************************************************************************************************
; 3.3 Go Turtles Procedure
;*******************************************************************************************************************************

to go-boars

  if ( shade-of? green pcolor ) [ eat-forest ]                                    ; if there is forest of green color, then eat it
  move-turtle 10                                                                  ; if not, move up to 10 patches

  reproduce-boars                                                                 ; give birth
  if human-threats [die-crossing-streets]                                         ; if "human-threats" is active, boars & deer might die when crossing streets  (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
end 

to go-deer

  if ( shade-of? green pcolor ) [ eat-forest ]                                    ; if there is forest of green color, then eat it
  move-turtle 20                                                                  ; if not, move up to 20 patches

  reproduce-deer                                                                  ; give birth
  if human-threats [ die-crossing-streets ]                                       ; if "human-threats" is active, deer might die when crossing streets  (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
end 

to go-livestock

  reproduce-livestock                                                             ; give birth                                                          (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
end 

to go-wolves

  catch-prey                                                                      ; wolves catch their prey

  reproduce-wolves                                                                ; give birth
  if human-threats [ die-crossing-streets ]                                       ; if "human-threats" is active, wolves might die when crossing streets

;*******************************************************************************************************************************
; 3.4 Management Procedure
;*******************************************************************************************************************************

  if wolf-management = "no-management"                                            ; if "no-management" is active,
    [catch-prey]

  ifelse wolf-management = "problem-wolves"                                       ; if "problem-wolves" is active,
  [ catch-prey1 ] [ catch-prey ]
  ask wolves with [ threat-level > wolf-tolerance ] [ set color 125 ]             ; wolves with a threat level above the tolerance level turn magenta

  ifelse wolf-management = "wooden-fence"                                         ; if "wooden-fence" is active,
    [ catch-prey2 ] [catch-prey]

  ifelse wolf-management = "electric-fence"                                       ; if "electric-fence" is active,
    [catch-prey3] [catch-prey]

  ifelse wolf-management = "shepherd-dog"                                         ; if "shepherd-dog" is active
    [catch-prey4] [catch-prey]

  if ProtectSettlements                                                           ; if "ProtectSettlements" is active,
    [protect-Settlements]
end 

to go-hunters

  hunt-prey                                                                       ; hunters hunt their prey

  if wolf-management = "problem-wolves"                                           ; if "problem-wolves" is active,
    [ hunt-wolves ]

  if wolf-management = "protect-fields"                                           ; if "protect-fields" is active,
    [protect-fields]

  if wolf-management = "kill-wolves"                                              ; if "kill-wolves" is active,
    [kill-wolves]
end 

;*******************************************************************************************************************************
; 3.5 Die Crossing Streets Procedure
;*******************************************************************************************************************************

to die-crossing-streets                                                           ; if "human-threats" is active,

  let chance-to-die random-float 100                                              ; there is a chance for turtles to die
  ifelse one-of neighbors = shade-of? blue pcolor                                 ; when the neighboring patch is blue ( a street )
  and chance-to-die < 0.026 [ die ] [ fd 2 ]                                      ; in case they survive, the turtles move
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 4. Move Turtle Procedure
;*******************************************************************************************************************************

to move-turtle [ maximum-speed ]                                                  ; each turtle has its own maximum speed
                                                                                  ; the overall moment is divided into maximum-speed steps
  repeat maximum-speed                                                            ; which are repeated as often as the maximum-speed value
   [ let speed random-float 1                                                     ; in each of these steps, the turtles move forward max. 1 patch
     carefully
     [ face one-of neighbors with [ shade-of? green pcolor ]                      ; in each step, preferably a forest patch is looked for          (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
     ]
     [ rt random 360
     ]
       fd speed
   ]
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 5. Reproduce Procedure
;*******************************************************************************************************************************

to reproduce-boars                                                                ; boar procedure

  if month = 3 or month = 4                                                       ; boars give birth in march and april
   [ if random-float 100 < 0.61                                                   ; throw "dice" to see if you will reproduce
      [ hatch 1 + random 3                                                        ; hatch between 1 and 4 offsprings and
        move-to one-of patches with [ pcolor = 56 ]                               ; move to a green forest patch
      ]
   ]
end 

to reproduce-deer                                                                 ; deer procedure

  if month = 5 or month = 6                                                       ; deer give birth in may and june
   [ if random-float 100 < 0.58                                                   ; throw "dice" to see if you will reproduce                                         (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
      [ hatch 1 + random 1                                                        ; hatch 1 or 2 offsprings and
        move-to one-of patches with [ pcolor = 56 ]                               ; move to a green forest patch
      ]
   ]
end 

to reproduce-wolves                                                               ; wolf procedure

  if month = 4 or month = 5                                                       ; give birth in april and may
   [ if random-float 100 < 0.50                                                   ; throw "dice" to see if you will reproduce
      [ hatch 1 + random 2 [ set threat-level 1 set color black ]                 ; hatch between 1 and 3 packs, reset threat-level and color
        move-to one-of patches with [ pcolor = 56 ]                               ; move to a green forest patch
      ]
    ]
end 

to reproduce-livestock                                                            ; livestock procedure

  if random-float 100 < 0.03                                                      ; throw "dice" to see if you will reproduce                                         (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
    [ hatch 1                                                                     ; hatch offspring and
      [rt random-float 360 fd 1 ]                                                 ; move forward 1
    ]
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 6. Eat and Grow Forest Procedure
;*******************************************************************************************************************************

to eat-forest                                                                     ; boar & deer procedure

  set  pcolor  brown                                                              ; when it eats forest, the patch turns brown
end 

to grow-forest                                                                    ; patch procedure

 if pcolor = brown                                                                ; countdown on brown patches                                                        In Anlehnung an Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017
  [ ifelse countdown <= 0                                                         ; if reach 0, grow some forest
    [ set pcolor 56
      set countdown 14                                                            ; countdown starts by 14
    ]
    [ set countdown countdown - 1                                                 ; every tick the countdown is reduced by 1
    ]
  ]
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 7. Catch Procedure
;*******************************************************************************************************************************

to catch-prey                                                                     ; wolf procedure

  let prey min-one-of ( turtles with                                              ; wolve's prey is a random livestock, deer or boar                                  (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
    [ breed = livestock or
      breed = deer or
      breed = boars
    ] in-radius 40 ) [ distance myself ]                                          ; in radius of 20 km

  ifelse prey != nobody                                                           ; if there is some prey
    [ ifelse distance prey > 5                                                    ; in radius > 5,
      [ face prey                                                                 ; face it,
        fd 5                                                                      ; move and
      ]
      [let chance-to-catch random-float 100
        ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
      ]                                                                           ; This chance was derived from trial runs of the model
    ]
    [ move-turtle random 50                                                       ; if there is no prey, move
    ]
end 

;*******************************************************************************************************************************
; 7.1 Problem Wolves
;*******************************************************************************************************************************

to catch-prey1                                                                    ; wolf procedure

  let prey1 min-one-of ( turtles with                                             ; wolve's prey1 is a random livestock
    [ breed = livestock
    ] in-radius 40 ) [ distance myself ]                                          ; in radius of 20 km

  let prey min-one-of ( turtles with                                              ; wolve's prey is a random deer or boar
    [ breed = deer or
      breed = boars
    ] in-radius 40 ) [ distance myself ]                                          ; in radius of 20 km

  ifelse prey1 != nobody                                                          ; if there is some prey1
    [ ifelse distance prey1 > 5                                                   ; in radius > 5,
      [ face prey1                                                                ; face it,
        fd 5                                                                      ; move and
      ]
      [let chance-to-catch random-float 100
        ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
        set threat-level threat-level + 1                                         ; and set threat-level +1
      ]
    ]

    [ move-turtle random 50                                                       ; if there is no prey, move
    ]

  ifelse prey != nobody                                                           ; if there is some prey
    [ ifelse distance prey > 5                                                    ; in radius > 5,
      [ face prey                                                                 ; face it,
        fd 5                                                                      ; move and
      ]
      [let chance-to-catch random-float 100
        ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
      ]
    ]
    [ move-turtle random 50                                                       ; if there is no prey, move
    ]

  ifelse one-of neighbors = shade-of? red pcolor                                  ; when wolves get near a settlement
    [ let chance-to-be-seen random-float 100
      if chance-to-be-seen < 5 [set threat-level threat-level + 0.5] ]            ; if the wolves get seen
    [ move-turtle random 20 ]                                                     ; their threat-level increases by half a level, otherwise they move
end 

to hunt-wolves                                                                    ; hunter procedure

  let prey1 min-one-of ( turtles with                                             ; hunters prey1 are wolves
      [ breed = wolves and color = 125                                            ; with a threat-level > 10
      ] in-radius 40 ) [ distance myself ]                                        ; in radius of 20 km

  let prey min-one-of ( turtles with                                              ; hunters prey are deer and boar
    [ breed = deer or
      breed = boars in-radius 5 ]) [ distance myself ]                            ; in radius of 2.5 km

  ifelse prey != nobody                                                           ; if there is some,
    [ let chance-to-catch random-float 100
      if chance-to-catch < 0.5 [ask prey [ die ]]                                 ; there is a chance to kill it
    ]
    [ right random 50                                                             ; if not, move
      left random 50
      forward 1
    ]

    ifelse prey1 != nobody                                                        ; if there is some prey1
    [ ifelse distance prey1 > 10                                                  ; in radius > 5,
      [ face prey1                                                                ; face it
        fd 10                                                                     ; and move
      ]
      [ let chance-to-catch random-float 100
      if chance-to-catch < 10 [ ask prey1 [ die ]]                                ; there is a chance to kill it
      ]                                                                           ; this chance was derived from the assumption that the hunter kills a single wolf 75 out of 100 times
      ]                                                                           ; And was further reduced by a factor of 7.5 since a single wolf turtle represents a pack of wolves
    [ right random 50                                                             ; if not, move
      left random 50
      forward 1
    ]
end 

;*******************************************************************************************************************************
; 7.2 Wooden Fence
;*******************************************************************************************************************************

to catch-prey2                                                                    ; wolf procedure

  let prey1 min-one-of ( turtles with                                             ; prey1 is a-livestock in radius 20
    [ breed = livestock ] in-radius 20 ) [ distance myself ]

  let prey min-one-of ( turtles with                                              ; prey one of the breeds in radius 20                                   (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)
    [ breed = deer or
      breed = boars ] in-radius 20 ) [ distance myself ]

  ifelse prey != nobody                                                           ; if there is some prey (in radius 20):

    [ ifelse distance prey > 5                                                    ; if the prey is in radius > 5,
      [ face prey                                                                 ; face it, move and
        fd 5
  ]
      [let chance-to-catch random-float 100
        ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
    ]
  ]
                                                                                  ; if there is no prey but prey1 (livestock)
    [ ifelse prey1 != nobody
      [ ifelse distance prey1 > 5                                                 ; if prey1 is in radius > 5,
        [ face prey1                                                              ; face it, move and
          fd 5
        ]
        [let chance-to-catch random-float 100
          ifelse chance-to-catch < 0.5 [ask prey1 [die]][move-turtle random 20]   ; kill it in 0.5% of the cases, otherwise move
      ]                                                                           ; the wooden fence leads to a lower chance-to-catch threshold for livestock only
    ]
      [ move-turtle random 50                                                     ; if not, move
      ]
    ]
end 

;*******************************************************************************************************************************
; 7.3 Electric Fence
;*******************************************************************************************************************************

to catch-prey3                                                                    ; wolf procedure


  let prey1 min-one-of ( turtles with                                             ; prey1 is a-livestock in radius 30
    [ breed = livestock ] in-radius 20 ) [ distance myself ]

  let prey min-one-of ( turtles with                                              ; prey is one of the breeds in radius 20
    [ breed = deer or
      breed = boars ] in-radius 20 ) [ distance myself ]

  ifelse prey != nobody                                                           ; if there is some prey (in radius 30):                                     (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)

    [ ifelse distance prey > 5                                                    ; if prey is in radius > 5,
      [ face prey                                                                 ; face it, move and
        fd 5
      ]
      [ let chance-to-catch random-float 100
         ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
    ]
  ]
                                                                                  ; if there is no prey but prey1 (livestock)
    [ ifelse prey1 != nobody
      [ ifelse distance prey1 > 5                                                 ; if prey1 is in radius > 5,
        [ face prey1                                                              ; face it, move and
          fd 5
        ]
        [let chance-to-catch random-float 100
          ifelse chance-to-catch < 0.25 [ask prey1 [die]][move-turtle random 20]  ; kill it in 0.25% of the cases, otherwise move
      ]                                                                           ; the electrical fence leads to a lower chance-to-catch threshold for livestock only
    ]
      [ move-turtle random 50                                                     ; if not, move
      ]
    ]
end 

;*******************************************************************************************************************************
; 7.4 Shepherd Dog
;*******************************************************************************************************************************

to catch-prey4                                                                    ; wolf procedure

  let prey1 min-one-of ( turtles with                                             ; prey1 is a-livestock in radius 20
    [ breed = livestock ] in-radius 20 ) [ distance myself ]

  let prey min-one-of ( turtles with                                              ; prey one of the breeds in radius 20
    [ breed = deer or
      breed = boars ] in-radius 20 ) [ distance myself ]

  ifelse prey != nobody                                                           ; (Sagolla & Kloeffer, "Woelfe in Niedersachsen", 2017)

    [ ifelse distance prey > 5                                                    ; if prey is in radius > 5,
      [ face prey                                                                 ; face it, move and
        fd 5
      ]
      [let chance-to-catch random-float 100
        ifelse chance-to-catch < 1 [ask prey [die]][move-turtle random 20]        ; kill it in 1% of the cases, otherwise move
    ]
  ]
                                                                                  ; if where is no prey but prey1 (livestock)
    [ ifelse prey1 != nobody
      [ ifelse distance prey1 > 5                                                 ; if prey1 is in radius > 5,
        [ face prey1                                                              ; face it, move and
          fd 5
        ]
        [let chance-to-catch random-float 100
          ifelse chance-to-catch < 0.125 [ask prey1 [die]][move-turtle random 20] ; kill it in 0.125% of the cases, otherwise move
      ]                                                                           ; the shepherd dog leads to a lower chance-to-catch threshold for livestock only
    ]
      [ move-turtle random 50
      ]                                                                           ; if not, move
    ]
end 

;*******************************************************************************************************************************

;*******************************************************************************************************************************
; 8. Hunt Procedure
;*******************************************************************************************************************************

to hunt-prey                                                                      ; hunter procedure

  let prey min-one-of ( turtles with                                              ; if "kill-wolves" is not active,
    [ breed = deer or                                                             ; the hunters prey are deer or boars
      breed = boars ] in-radius 5 ) [ distance myself ]                           ; in radius of 2.5 km

  ifelse prey != nobody                                                           ; if there is some,
    [ let chance-to-catch random-float 100
      if chance-to-catch < 0.5 [ ask prey [ die ]]                                ; there is a chance to kill it
    ]
    [ right random 50                                                             ; if not, move
      left random 50
      forward 1
    ]
end 

;*******************************************************************************************************************************
; 8.1 Kill Wolves
;*******************************************************************************************************************************

to kill-wolves                                                                    ; hunter procedure

  let prey min-one-of ( turtles with                                              ; if "kill-wolves" is active,
    [breed = deer or                                                              ; hunters prey are deer or
     breed = boars ] in-radius 5 ) [ distance myself ]                            ; boars in radius of 2.5 km

 let prey1 min-one-of ( turtles with
    [breed = wolves ]
    in-radius 5 ) [distance myself]

  ifelse prey != nobody                                                           ; if there is some,
   [ let chance-to-catch random-float 100
      if chance-to-catch < 0.5 [ ask prey [ die ]]                                ; there is a chance to kill it

  ]
    [ carefully
      [ face one-of neighbors with
        [ shade-of? green pcolor or shade-of? yellow pcolor
        ]
      ]
      [ rt random 360
      ]                                                                           ; if not, move
      fd 1
    ]

  ifelse prey1 != nobody                                                          ; if there are wolves,
   [ let chance-to-catch random-float 100
      if chance-to-catch < 0.5 [ ask prey [ die ]]                                ; there is a chance to kill it

  ]
    [ carefully
      [ face one-of neighbors with
        [ shade-of? green pcolor or shade-of? yellow pcolor
        ]
      ]
      [ rt random 360
      ]                                                                           ; if not, move
      fd 1
    ]
end 

;*******************************************************************************************************************************
; 8.2 Protect Fields
;*******************************************************************************************************************************

to protect-fields                                                                 ; hunter procedure

  let prey min-one-of ( turtles with                                              ; if "kill-wolves" is active,
    [breed = deer or                                                              ; hunters prey are deer or
     breed = boars ] in-radius 5 ) [ distance myself ]                            ; boars in radius of 2.5 km


  let prey1 min-one-of ( turtles with                                             ; if "protect-fields" is active,
    [ breed = wolves] in-radius 5 ) [ distance myself ]                           ; hunters prey are wolves in radius of 2.5 km

  ifelse prey1 != nobody                                                          ; if there is some,
      [ifelse shade-of? yellow pcolor [ask prey1 [ die ]][ fd 1]                  ; hunter kills the whole pack
    ]
    [ carefully
      [ face one-of neighbors with
        [ shade-of? yellow pcolor                                                 ; when a hunter is on a field, he will shoot wolves in the proximity
      ]
    ]
      [ rt random 360
      ]                                                                           ; if not, move
      fd 1
    ]

  ifelse prey != nobody                                                           ; if there is some other prey,
   [ let chance-to-catch random-float 100
      if chance-to-catch < 0.5 [ ask prey [ die ]]                                ; there is a chance to kill it

  ]
    [ carefully
      [ face one-of neighbors with
        [ shade-of? green pcolor or shade-of? yellow pcolor
        ]
      ]
      [ rt random 360
      ]                                                                           ; if not, move
      fd 1
    ]
end 

;*******************************************************************************************************************************
; 8.3 Protect Settlements
;*******************************************************************************************************************************

to protect-settlements

  let chance-to-be-shot random-float 100                                          ; chance-to-be-shot is a random number between 0 and 99
  ifelse one-of neighbors = shade-of? red pcolor                                  ; if one of neighbor-patches red (settlement) and the random number is smaller than 0.026
  and chance-to-be-shot < 5 [ask wolves [die] ][move-turtle random 1]             ; turtles here die, if it is larger, the animal moves away in a random direction
end 

;*******************************************************************************************************************************
;*******************************************************************************************************************************