Predation in caves: the effects of prey immobility and darkness on the foraging behaviour of two salamanders, Euproctus asper and Proteus anguinus.

The behavioural responses of the blind cave salamander Proteus anguinus and the Pyrenean salamander Euproctus asper (a facultative cave dweller) to living and dead chironomids offered in light or in darkness were studied experimentally. Both species were able to detect and locate single prey items positioned at distances of 30 cm. Proteus responded to dead prey in light faster and captured live prey in darkness earlier than E. asper. E. asper captured live prey in light earlier than in darkness. Proteus is well equipped to search for non-visual information and used an active, mechanically and chemically guided approach in all experiments. E. asper showed a more directed, visually dominated approach behaviour with live chironomids in light, but used an active, widely foraging mode with live prey in darkness and dead prey in light. E. asper may forage successfully both in epigean and hypogean habitats.