LOCALIZED DEFECATION BY PIKE - A RESPONSE TO LABELING BY CYPRINID ALARM PHEROMONE

Fathead minnows (Pimephales promelas) that have never encountered a pr edatory pike (Esox lucius), are able to detect conspecific alarm phero mone in a pike's diet if the pike has recently consumed minnows. It re mains unclear how this minnow alarm pheromone is secreted by pike and if a pike is able to avoid being labelled as a potential predator by l ocalizing these cues away from its foraging range. The first experimen t determined that minnow alarm pheromone is present in pike feces when pike are fed minnows. Individual fathead minnows exhibited a fright r esponse to a stimulus of pike feces if the pike had been fed minnows, but not if the pike had been fed swordtails, which lack alarm pheromon e. Individual minnows also exhibited a fright reaction to alarm pherom one in the water (which contained no feces) housing pike which had bee n fed minnows, suggesting that alarm pheromone is also released in uri ne, mucous secretions and/or via respiration. The second experiment de termined that test pike spent a significantly greater proportion of ti me in the ''home area'' of the test tanks (i.e. where they were fed) b ut the majority of feces were deposited in the opposite end of the tes t tank. By localizing their defecation away from the home or foraging area, pike may be able to counter the effects of being labelled as a p redator by the alarm pheromone of the prey species.