Study of Individual and Study of Individual and Group responses of Group responses of Mexican Free Tailed Mexican Free Tailed
BatsBats
Presented by
Aruna Raghavan
Brief Introduction to the Brief Introduction to the Ecological AspectsEcological Aspects
• Bats live as colonies in caves• They emerge only during the night and
communicate using the Echo-location principle• Most of the bat colonies are located in Texas.
Some of the bat caves are the Frio caves, Carlsbad caves, Ney caves etc.
• Study of Bat flight and counting the number of bats present in these caves is the challenge here…!!
Frio Cave, TexasFrio Cave, Texas
Pre Emergence VortexPre Emergence Vortex
Column FormationColumn Formation
Column formationColumn formation
Disturbance due to a hawkDisturbance due to a hawk
Bat Emergence : Thermal VideoBat Emergence : Thermal Video
Bat ModelingBat Modeling
A simple Visual C++ based approach
depicting the different rules followed by
the bats to remain inside the column is
being studied.
Boids HistoryBoids History
• Craig Reynolds – 1976 – Looked at bird flocking– Used individual based approach with rules
describing movement
• Nice real-time graphics developed – Platt (2000) 3D-boids
Basic RulesBasic Rules
• Flock forming• Collision Avoidance• Velocity Matching• Community Predator Avoidance• Individual Predator Avoidance• Foraging• Sub Flocking
Flock FormingFlock Forming
The current bat is indicated using
a green triangle. As the simulation
proceeds, the program checks for
bats that are in the neighborhood
of the current bat being iterated on.
If any bat is detected, then it is
moved to the center of mass of the
group (showed as a green dot).
This will result in the formation of a
LOCAL BAT FLOCK.
Flock forming PseudocodeFlock forming Pseudocode
PROCEDURE flock forming rule1(boid bJ)
Position Vector pcJ
FOR EACH BOID b
IF b != bJ THEN
pcJ = pcJ + b.position END IF
END
pcJ = pcJ / N-1
RETURN (pcJ - bJ.position) / 100 END PROCEDURE
Collision AvoidanceCollision Avoidance
The bat that is being currently
iterated is shown as a green triangle.
The program checks for other bats
that are in the close neighborhood of
the current bat. If the distance
exceeds a certain value, the bats
move apart. This is done as a
precautionary measure to avoid
any bat collisions.
Collision avoidance PseudocodeCollision avoidance Pseudocode
PROCEDURE Collision avoidance rule(boid bJ) Vector c = 0;
FOR EACH BOID b IF b != bJ THEN
IF |bJ.position - b.position| < 100 THEN c = c - (bJ.position -
b.position) END IF
END IF END RETURN c
END PROCEDURE
Velocity MatchingVelocity Matching
In this rule, the bats that are in the neighborhoodtry to match the velocityof the current bat. This willlead to a uniform velocityfor all the bats in the entire column.
Velocity Matching Pseudocode
PROCEDURE Velocity Matching rule(boid bJ)
Vector pvJ FOR EACH BOID b
IF b != bJ
THEN pvJ = pvJ + b.velocityEND IF
END
pvJ = pvJ / N-1
RETURN (pvJ - bJ.velocity) / 8 END PROCEDURE
Other Avoidance rulesOther Avoidance rules
Community PredatorAvoidanceThis concept will be more clear in the simulation. The batsalong the ends of thecolumn, try to comeinside the column.
Individual PredatorAvoidance:In this rule, all the bats inside the column tend tomove towards the centerof mass of the column. This will lead to a line like formation but they willbe spatially separated toavoid collisions.
Other Behavioral AspectsOther Behavioral Aspects
Foraging:
This shows how the
bats forage in open
fields with all the rules
still operating.
Sub Flocking:
The bats tend to
separate into sub columns
after flying in a single
column for a long time.
BATOIDS SIMULATION
Dynamic Frame Bat Counting
Thousands of bats come out of the caveas shown in the video. The problems faced while counting are :• Presence of one bat behind another bat• The flow rate is not constant. By this I
mean, the number of bats entering one frame is not the same as the number of bats leaving the frame.
• The problem of OCCLUSION • Errors caused due to overcounting and
undercounting
The Bat video
Proposed Work
• Counting of the bats during emergence
• Trying to link the simulation with the real time video by using it as the initial conditions and studying the bat flight
• Add a few more rules to the simulation
Thank You !