PRIORITY USE OF CHEMICAL OVER VISUAL CUES FOR DETECTION OF PREDATORS BY GRAYBELLY SALAMANDERS, EURYCEA MULTIPLICATA GRISEOGASTER

摘要

Many aquatic amphibians live in habitats with low visibility. In such habitats, chemical cues may be more reliable than visual cues for predator recognition. Adult perrenibranchiate graybelly salamanders, Eurycea multiplicata griseogaster, occupy clear-water streams with low levels of sedimentation and relatively few visual obstructions. In a previous laboratory experiment, graybelly salamanders distinguished between chemical stimuli from predatory fish (banded sculpins, Cottus carolinae) and nonpredatory tadpoles (Rana sphenocephala). In the present study, when only visual cues were available, salamanders did not distinguish between sculpins and tadpoles. Instead, they reduced activity in response to both predatory and nonpredatory heterospecifics in comparison to a blank control, indicating an alarm response to general disturbance rather than recognition of the specific predator, per se. To confirm that chemical stimuli are important under natural conditions, we tested whether graybelly salamanders in a natural stream habitat distinguished between chemical stimuli from sculpins, nonpredatory fish (stonerollers, Campostoma pullum), and a blank control. In contrast to their response to the nonpredator treatments, salamanders quickly moved away from the sculpin stimulus and then burrowed into the gravel substrate. Therefore, even for salamanders from clear-water habitats, chemical stimuli are more effective than visual stimuli for recognition of visually cryptic predators.