Behavioral response of solitary fathead minnows,Pimephales promelas, to alarm substance.

Single fathead minnows,Pimephales promelas, were exposed to a range of concentrations of conspecific skin extract. Their responses were observed qualitatively and quantified by a computer linked to an activity meter. The response of fathead minnows to skin extract is complex, involving at least three separate types of behavior. The minnows responded over a 1000-fold range of extract concentrations with combinations of dashing, freezing, slowing, and exploring. The latency of the response increased at the lowest extract concentrations, suggesting summation of sensory cell responses. At low stimulus concentrations, a period of exploratory behavior sometimes preceded the more typical alarm responses. The active space generated by the alarm substance in 1 cm(2) of minnow skin may exceed 58,000 liters.