Chemical “versus” visual cues in newts (Salamandridae): experiments in total darkness and in a Y-maze

The use of pheromones for sexual communication has been observed in many species of the family Salamandridae. Most research was done on a species of the genus Cynops, where a species-specific male decapeptide was identified and pheromonal activity was described in detail. Here we performed two tests to analyze the relative importance of intersexual chemical and visual communication in two genera of newts during their reproductive season. To check for female attraction by a pheromone, we designed an experiment using a Y-maze apparatus. It demonstrated that female newts are significantly more attracted to a male experimentally accompanied by a pheromone, than to a male without that stimulus (p=0.008, N=13). However, after sensing the chemical stimulus, the visual stimulus seems to become equally important (p=0.048, N=13). To better understand the relative importance of pheromone communication, we subsequently observed courtship behaviour in complete darkness using a camera and an infrared reflector. Here we observed that courtship could be induced, i.e. the female approached the male and the male responded by tail waving, but there was no reproductive success. We conclude that, in experimental conditions, chemical signals from both sexes are necessary and sufficient for attraction and initiation of courtship behaviour, but visual cues become equally important after chemical stimulus has been recognized by the animal.