;; This model was designed by Lilly A. Whitney and Lawrence A. Whitney globals [ wheading ] breed [ bats bat ] breed [ moths moth ] breed [ waves wave ] bats-own [ food ] waves-own [ energy ] to setup clear-all create-bats number-of-bats [ set shape "hawk" set color brown set size 3 setxy random-xcor random-ycor ] ;; Give each bat a consecutive number starting at 0. let num 0 ask bats [ set label num set num num + 1 ] create-moths number-of-moths [ set shape "butterfly 2" set color white set size 1 setxy random-xcor random-ycor ] reset-ticks end to go ask turtles [ if breed = moths [ moth-fly ] if breed = bats [ chirp ;; Has bats create sound waves that help them find moths. bat-fly ;; Has bats fly towards moths that they find using chirp. ] ] if not any? moths [ stop ] tick end to moth-fly set heading heading + ( 360 * random-normal 0 0.1 ) repeat 5 [ ask moths [ fd 0.1 ] display ] end to chirp ;; wave grows outward from bat ;; waves that intersect moth stop, all others die ;; bat turns to face waves/moth let degree 0 ;; creates a wave of 72 agents, 1 agent per 5 degrees hatch-waves 72 [ set shape "dot" set size 0.5 set color 96 set label "" set energy wave-energy set heading heading + degree set degree degree + 5 ] ;; Wave moves outward until it hits a moth. ;; Energy is how far a wave can go before it dies out. loop [ ifelse count waves > 1 [ ask waves [ if energy < 1 [ die ] fd 0.3 display set energy energy - 1 if any? moths-here [ ask other waves [ die ] set wheading heading stop ] ] ] [ ifelse count waves = 1 [ ;; Determines if the moth the wave found is within the bats detection range. ;; If moth is within detection range, turns bat toward the moth. ifelse abs ( subtract-headings heading wheading ) <= detection-range [ face one-of waves ask waves [ die ] stop ] [ ask waves [ die ] stop ] ] [ stop ] ] ] end to bat-fly ;; Bats move according to their headings and eat any moths they encounter. repeat 15 [ ;; bats determine if other bats are in their way, and if so turn to try to avoid them if any? other bats in-cone 5 detection-range [ let direction random 2 if direction = 0 [ set heading heading - bat-avoid ] if direction = 1 [ set heading heading + bat-avoid ] ] fd 0.2 display if any? moths-here [ set food food + count moths-here ask moths-here [ die ] ] ] output-show food ;; Keeps a running tab of how many moths each bat has eaten. ask waves [ die ] end @#$#@#$#@ GRAPHICS-WINDOW 240 10 721 492 -1 -1 14.33333333333334 1 10 1 1 1 0 1 1 1 -16 16 -16 16 0 0 1 ticks 30.0 BUTTON 27 82 90 115 NIL setup NIL 1 T OBSERVER NIL NIL NIL NIL 1 BUTTON 130 85 193 118 NIL go T 1 T OBSERVER NIL NIL NIL NIL 1 SLIDER 23 158 226 191 number-of-bats number-of-bats 1 10 5.0 1 1 NIL HORIZONTAL SLIDER 21 214 229 247 number-of-moths number-of-moths 0 100 11.0 1 1 NIL HORIZONTAL SLIDER 20 266 226 299 wave-energy wave-energy 1 30 15.0 1 1 NIL HORIZONTAL OUTPUT 748 373 988 453 11 TEXTBOX 752 350 902 368 Moths each bat has eaten: 11 0.0 1 SLIDER 20 319 226 352 detection-range detection-range 5 180 45.0 5 1 degrees HORIZONTAL SLIDER 22 375 227 408 bat-avoid bat-avoid 1 30 30.0 1 1 degrees HORIZONTAL @#$#@#$#@ ## WHAT IS IT? This is a model of bats using echolocation to catch moths. The bats chirp, producing sound waves that indicate the direction of any moths they intersect. ## HOW IT WORKS Bats and moths are randomly distributed in the world of the model. The bats then echolocate the moths by chirping sound waves that move outward from the bat until they intersect with the nearest moth, if any. The bat turns to face the moth identified by the sound wave it generated. When bats fly into the same space as a moth, they catch and eat it. Bats ignore moths identified outside of their detection range, a cone of variable degree set by the user. They also avoid other bats that fly into their detection range. When there are no moths left, the model stops. ## HOW TO USE IT When you press the setup button, bats and moths will be randomly distributed throughout the world of the model and the bats will be labeled with a number. Interface sliders may be used prior to setup to set the population of bats, the population of moths, the energy of the echolocation waves the bats generate, which determines the radius of each echolocation sound wave, the detection range, which is the angle in front of each bat in which detected moths will be hunted, and the angle at which bats will turn to avoid other bats. When you press go, the bats and moths fly in random order, the moths turning randomly and then moving, whereas the bats only turn before moving if their echolocation identifies a moth or they will run into another bat. Each bat hatches a sound wave that moves outward, stopping if it detects a moth or when it runs out of energy. Bats turn toward any moths their sound waves identify. To be able to see the sound waves propagate, turn the tick rate slower. The number of moths each bat has eaten is shown in the monitor. ## THINGS TO NOTICE First, if you cannot see the sound waves the bats are generating, turn down the tick rate and they will become visible. You may also notice that moth flight is mostly random whereas the bats fly in a straight line unless they find a moth or encounter another bat. Because bats and moths cycle through their procedures in random order each turn, it is possible for a moth to escape getting eaten if it gets two moves after being identified before the bat moves again as long as its movement carries it outside the detection range of the bat. ## THINGS TO TRY How does increasing or decreasing the number of bats, the number of moths, or both change the average number of ticks it takes for the bats to catch all of the moths? You could answer this question by conducting an experiment with the model in BehaviorSpace. You may also want to see how expanding or contracting the detection range of the bats improves or hinders their hunting ability. Likewise, you can see how increasing to decreasing the energy of the echolocation waves, which impacts how far they range from the bat that chirps them, impacts hunting effectiveness. ## EXTENDING THE MODEL Right now, bats simply avoid other bats that are in their detection range within three patches. You could program them to avoid other bats using their echolocation. You could also add obstacles, such as trees or stalagmites or stalactites, and have the bats use their echolocation to avoid them, and have them die if they fail. ## NETLOGO FEATURES This model uses three breeds, one of which, waves, is hatched from the bat breed, spreading out and identifying the direction of any adjacent moth all during a single tick. The model uses subtract-headings to determine whether an identified moth is within the detection range of the bat that found it, and uses in-cone to avoid other bats in the detection-range. The use of subtract-headings with respect to the moths is to more closely mimic the way that bats use their echolocation to determine whether a moth is in-cone rather than relying on background functions in NetLogo, meaning it's more like real life. ## RELATED MODELS Flocking Model (in the model library) Wolf Sheep Predation (in the model library) [Doppler Effect Model] (https://ccl.northwestern.edu/netlogo/models/community/doppler_effect_model) ## CREDITS AND REFERENCES This model was created by Lilly A. Whitney and Lawrence A. Whitney. We were aided in understanding bats and echolocation by reading an article on [How Stuff Works] (https://animals.howstuffworks.com/mammals/bat.htm) and by visiting an exhibit on bats at the Peabody Essex Museum in Salem, Massachusetts. This model is available on Netlogo User Community Models. ## LICENSE Attribution should be made to Lilly A. Whitney and Lawrence A. Whitney. This work is licensed under [CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/?ref=chooser-v1) ![CC BY-NC-SA 3.0](http://ccl.northwestern.edu/images/creativecommons/byncsa.png) @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 225 150 285 150 135 Line -16777216 false 150 285 150 135 Line -16777216 false 150 135 15 75 Line -16777216 false 150 135 285 75 bug true 0 Circle -7500403 true true 96 182 108 Circle -7500403 true true 110 127 80 Circle -7500403 true true 110 75 80 Line -7500403 true 150 100 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