Experimental analysis of the prey catching behavior ofHydromantes italicus Dunn (Amphibia, Plethodontidae)

Summary

1. The Italian bolitoglossine salamanderHydromantes italicus shows a periodic cave life. In spring and in the fall it leaves the caves after which it lives under stones, in leaves and crevices. Inside the limestone caves,H. i. can be found both in the zone of dim light near the entrance and in total darkness. 2. Corresponding to these two environments there are two guidance systems of the prey catching behavior: one visual and one olfactory. 3. The visually guided prey catching behavior is determined by the stimulus parameters: velocity, size, contrast, and ambient illumination. Continuously moving objects are effective within a velocity range of 0.05 to 6 cm/s with an optimum at 1.25 cm/s (Fig. 2). Stimuli moving stepwise elicit fixation of the prey and complete approach more frequently than continuously moving stimuli. The prey size which elicits prey catching ranges from 0.5 to 10 mm² with an optimum size between 2.5–5.0 mm² (Fig. 3). The prey catching behavior is hardly impaired by a decrease in ambient illumination down to 0.03 cd/m². Beyond 0.03 cd/m², the prey catching activity decreases sharply, but there are still responses at an illumination level of 0.003 cd/m² (Fig. 4). 4.H.i. also responds to stationary non-smelling visual stimuli following stimulation by smell or movement.H.i. is able to detect prey by smell only both in total darkness and in the light (Fig. 5 A). In the light, the prey catching behavior with regard to smelling objects is inhibited by the absence of visual contrast (Fig. 5B).