Predator avoidance and school size in a cyprinodontid fish, the banded killifish (Fundulus diaphanus Lesueur)
Solitary and schooling banded killifish (Fundulus diaphanus Lesueur) were 'attacked' with a fish predator model in the littoral zone of a lake and their flight reaction distance to the model recorded. Reaction distance of solitary fish did not differ significantly from that of schooling fish, which was statistically constant over a wide range of observed school sizes. The results fo not support the proposed early predator warning function of social groups, which predicts an asymptotically increasing flight reaction distance with increasing group size. However, fish in larger and safer groups may detect an approaching predator sooner but delay their flight response, thereby permitting their individual members to spend more time assessing the nature of the threat before escaping. Such a strategy would reduce costly false alarms. Relative variation in recorded reaction distances was correlated negatively with school size, suggesting that schooling reduces variability in latency time to escape predators. This may be evidence for the above behavioural strategy. Further, the speed of transmission of the flight response within the school greatly exceeded the speed of approach of the predator model. This phenomenon enables schooling individuals to initiate avoidance behaviour before the approaching predator can be detected and before it reaches them.
|Journal||Behavioral Ecology and Sociobiology|
Godin, J.-G.J, & Morgan, M.J. (M.Joanne). (1985). Predator avoidance and school size in a cyprinodontid fish, the banded killifish (Fundulus diaphanus Lesueur). Behavioral Ecology and Sociobiology, 16(2), 105–110. doi:10.1007/BF00295142