Mid-sized groups perform best in a collective decision task in sticklebacks.

Area of Science:

• Animal behavior
• Ecology
• Evolutionary biology

Background:

• Collective behavior often improves with larger group sizes.
• The potential for decreased performance in very large groups is less understood.

Purpose of the Study:

• To experimentally investigate the relationship between group size and collective decision-making in three-spined sticklebacks.
• To determine if functional improvements in collective behavior saturate or decline with increasing group size.

Main Methods:

• Tested the latency of solitary and grouped three-spined sticklebacks (2-29 individuals) to leave an unfavorable habitat.
• Analyzed the relationship between group size and departure latency, and the timing of the first individual to leave.

Main Results:

• Initially, latency to leave decreased with increasing group size, confirming previous findings.
• Beyond a certain size, latency to leave increased, revealing a U-shaped relationship.
• An optimal group size for habitat departure was estimated between 12 and 20 fish.

Conclusions:

• Collective behavior benefits from group size up to an optimum, after which it can decline.
• Social conformity in larger groups may inhibit innovation and collective action.
• Findings highlight the importance of considering optimal group sizes for effective collective decision-making in animal groups.