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 !