DIFFERENTIAL LEARNING RATES OF CHEMICAL VERSUS VISUAL CUES OF A NORTHERN PIKE BY FATHEAD MINNOWS IN A NATURAL HABITAT

We stocked 39 juvenile pike, Esox lucius, into a previously pike free pond which contained a population of approximately 78 000 fathead minn ows, Pimephales promelas. Fathead minnows sampled prior to pike stocki ng did not show a stereotypic fright response to either visual or chem ical cues from pike. After stocking pike, we sampled minnows every two days for a period of two weeks. Minnows sampled six days after stocki ng still did not show a fright response to the sight of a pike, but th ose sampled eight days after stocking did exhibit a significant fright response, indicating that acquired predator recognition based on visi on occurred between six and eight days. Minnows sampled two days after stocking did not show a fright response to chemical cues of a pike. T hose sampled four days after did, however, exhibit a significant frigh t response, indicating that acquired predator recognition based on che mical cues occurred between two and four days. These data indicate tha t acquired predator recognition occurs very rapidly and that the rate of learning of predator identity differs for chemical versus visual cu es.