Scalable rules for coherent group motion in a gregarious vertebrate

Area of Science:

• Animal behavior
• Collective movement dynamics
• Social interaction mechanisms

Background:

• Gregarious species require cohesion mechanisms for group living advantages.
• Understanding individual movement decision rules is key to collective movement studies.
• Previous research often focused on group-level behaviors or lacked individual-scale quantification.

Purpose of the Study:

• To investigate individual decision-making rules in collective movement.
• To differentiate between external stimuli responses and social synchronization.
• To identify mechanisms maintaining group cohesion under leadership.

Main Methods:

• Triggering departure of trained Merino sheep from groups of varying sizes (1, 3, 5, 7 naïve individuals).
• Quantifying the temporal dynamics of individual responses based on departure rank.
• Analyzing social stimuli influencing individual movement decisions.

Main Results:

• Individual movement decisions do not follow a quorum response.
• A double mimetic effect governs movement: attraction to both departed and non-departed individuals.
• This rule is scalable and adaptive to different group sizes.

Conclusions:

• Collective movement in sheep is driven by a dual attraction strategy, not a quorum.
• This social mimicry mechanism ensures group cohesion and is adaptable to group size.
• Findings provide insights into leadership and social dynamics in gregarious species.