Emily McHenry

Biology 478

April 25, 2012

COLLECTIVE DECISION MAKING:

SYNCHRONOUS MOVEMENT OF

INDIVIDUALS IN GROUPS

WHAT IS COLLECTIVE BEHAVIOR?

http://www.youtube.com/watch?v=Ua2quxUDyRk&feature=related

(Start at 3:37)

Collective animal behavior:

the coordinated behavior of large groups of similar animals and the emergent properties of these groups (Couzin 2012).

WHAT IS COLLECTIVE BEHAVIOR?

worldhum.com

Flocks of birds

Swarms of insects

Schools of fi sh

Herds of mammals

EXAMPLES OF COLLECTIVE BEHAVIOR

aquariumprosmn.com

esa.orgdigital-photography-school.com

Increased foraging effi ciency (Bazazi 2012)

Energy effi ciency (Tamm 1980)

Aerodynamic and hydrodynamic benefits

Predation avoidance

Relies on selfish herd effect; increased group size results in lower

chances of any one individual becoming a victim

WHY DO ANIMALS MOVE SYNCHRONOUSLY?

There are 3 Distinct patterns of predation avoidance

Vacuolization: where expansion results in a cavity

forming around the predator

Flash expansion: where individuals rapidly move away from the predator as it

strikes

Split effect where the group fragments

Most common reason for aggregations, but not always beneficial! http://www.youtube.com/watch?v=XzZhSl_00pI&feature=related

PREDATION AVOIDANCE

Most research has

been done in two ways:

1. Filming groups and then

frame-by-frame analyzing

2. Swarm simulating software

STUDYING COLLECTIVE BEHAVIOR

princeton.edu

SWARM SIMULATIONS

http://www.youtube.com/watch?v=GUkjC-69vaw

Swarms are created following 3

fundamental rules:

Separation: steer to avoid crowding or

collisions

Alignment: steer toward the average

heading of groupmates

Cohesion: steer to move toward the average

position of local groupmates

Previously thought to be telepathic

Utilizing senses

Eyesight, pressure, hearing, etc.

Monitoring position of neighbors

Behavioral zones

Repulsion

Attraction

Alignment based on relative position

HOW DO ANIMALS MOVE SYNCHRONOUSLY?

Flocking Birds/Schooling Fish

Democracy

Quorum responses (Sumpter 2009)

Insects

No leader, forced march (Simpson 2006)

Mammals

Unknown

DECISION MAKING IN THE GROUP

QUESTIONS?

Potts, Wayne K. 1984. "The chorus-line hypothesis of coordination in avian flocks." Nature 24: 344-345.

Simpson, Stephen J, Gregory A. Sword, Patrick D. Lorch, and Iain D. Couzin. "Cannibal Crickets on a Forced March

for Protein and Salt." Proceedings of the National Academy of Sciences of the United States of America. 103.11

(2006): 4152-4156.

Bazazi, S. et al. (2012) Vortex formation and foraging in polyphonic spadefoot toad tadpoles. Behavioral Ecology

and Sociobiology. March 2012.

Tamm, Staff an. "Bird Orientation: Single Homing Pigeons Compared with Small Flocks."

Behavioral Ecology and Sociobiology . 7.4 (1980): 319-322.

Tien, J Rubenstein, D. “Dynamics of fi sh shoals: Identifying key decision rules.” Evolutionary

Ecology Research, No. 6. (2004), pp. 555-565

Ward, A.J.W, D.J.T Sumpter, I.D Couzin, P.J.B Hart, and J Krause. "Quorum Decision-Making

Facilitates Information Transfer in Fish Shoals." Proceedings of the National Academy of

Sciences of the United States of America . 105.19 (2008): 6948-6953.

Sumpter, D.J.T, and S.C Pratt. "Quorum Responses and Consensus Decision Making."

Philosophical Transactions of the Royal Society B: Biological Sciences . 364.1518 (2009): 743-

753.

Couzin, I D, and J Krause. "Self-organization and Collective Behavior in Vertebrates." Advances in the Study of

Behavior. 32 (2003): 1-75.

Couzin, I. D., J. Krause, R. James, G. D. Ruxton, and N. R. Franks. 2002. Collective memory and spatial sorting in

animal groups. Journal of Theoretical Biology 218: 1-11.

Caraco, T., S. Martindale, and H. R. Pulliam. 1980. Flocking: advantages and disadvantages. Nature 285: 400-401.

WORKS CITED