The response of prey to the risk of predation: proximate cues for refuging juvenile fish

When prey encounter predators, they use different cues to indicate how to respond to minimize the predation risk. How such proximate cues in the environment correspond to the ultimate behaviour of the prey are important for understanding the outcome of predator–prey interactions. The precision of the anti-predator response of juvenile perch, Perca fluviatilis, and roach, Rutilus rutilus, when subjected to predation by piscivorous perch and pike, Esox lucius, and to different types of structure was tested in a wading pool experiment. The predation risk was varied between two habitats (one open water and one structured) by confining the predators to one of the two habitats. The prey were free to choose between habitats. Both perch and pike attacked both prey species but they were only successful in capturing roach. Roach swam faster than juvenile perch in the presence of perch, whereas juvenile perch swam faster than roach in the presence of pike. Juvenile perch inspected the predators more and showed a more flexible inspection behaviour than did roach. Juvenile perch decreased the number of switches between habitats and stayed in the predator-free part of the pool in the presence of perch. In contrast, roach increased their habitat switch frequency in the presence of perch and stayed in the vegetation structure even when there were perch there. Both prey species preferred to stay in the vegetation structure when pike were there. Juvenile perch used both the vegetation and pipe structure as refuges whereas roach used only the vegetation structure as a refuge. The results suggest that juvenile perch use a different cue when assessing predation risk and display a more flexible behaviour compared with roach which simply move into vegetation under the threat of predation irrespective of predator location.