Behavioral Ecology and Sociobiology

, Volume 29, Issue 4, pp 271–276

Safety in numbers: shoal size choice by minnows under predatory threat

  • Mary C. Hager
  • Gene S. Helfman

DOI: 10.1007/BF00163984

Cite this article as:
Hager, M.C. & Helfman, G.S. Behav Ecol Sociobiol (1991) 29: 271. doi:10.1007/BF00163984


Larger animal groups often provide greater protection from predators. An individual might therefore be expected to join the larger of two groups. To test this, we hypothesized that fathead minnows would choose to associate with the larger of two shoals and that the presence of a predatory largemouth bass would influence their shoal size choice. Individual minnows were presented with a series of choices between two shoal sizes, ranging from 1 to 28 fish, both with and without a predator present. Although responses were highly variable, minnows displayed an ability to choose between shoal sizes even when size differences were small, preferring the larger shoal whenever a size preference was shown. In the presence of a predator, minnows made quicker shoaling decisions and showed a strong tendency to avoid very small shoals.

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Mary C. Hager
    • 1
  • Gene S. Helfman
    • 1
  1. 1.Department of Zoology and Institute of EcologyThe University of GeorgiaAthensUSA
  2. 2.Bowker A&I PublishingNew ProvidenceUSA