Differences in Biosonar Sound Characteristics between Cetacean Species in the Istanbul Strait

Abstract

Previous visual observation suggested there is a possibility of difference in habitat use between harbor porpoise (Phocoena phocoena) and bottlenose dolphin (Tursiops truncatus) in the Istanbul Strait (Bosphorus). However, no direct evidence of difference was recorded, except for the number and area of sightings so far. From 12 April to 1 June 2012, passive acoustic monitoring was conducted with visual observation. The click trains with visual confirmation of species were extracted to compare the difference of inter-click intervals between harbor porpoise and bottlenose dolphins. In the results, the inter-click intervals showed multimodal distribution, which had one peak around 40-50 ms and the other around 100-130 ms in bottlenose dolphins. On the other hand, harbor porpoises showed only one peak around 10-20 ms. These results suggest that two species are using biosonar for different sensing distances even in the same area.