Comparative approach of echolocation signals in the genus Lagenorhynchus and Cephalorhynchus in the Southern Hemisphere

MARINO ALEXANDER; REYES REYES MARIA VANESA; HEVIA MARTA; MELCÓN MARIANA

Workshop; Rethinking Lagenorhynchus: Taxonomy, genetics, acoustics, morphology, stock structure, status and conservation status. 21st Biennial Conference on the Biology of Marine Mammals; 2015

Society of Marine Mammalogy

Two types of echolocation signals are present within the Lissodelphininae subfamily: Broad-band clicks with short duration and Narrow-band high frequency clicks (commonly referred to as NBHF clicks), with long duration. The first type of echolocation signals is produced by Lagenorhynchus obscurus, L. obliquidens and Lissodelphis borealis; while the second type is produced by all Cephalorhynchus species, L. australis and L. cruciger. During visual and acoustic surveys in Antarctic and sub-antarctic waters we were able to record Hourglass dolphin?s echolocation clicks near the South Shetland Islands in 2 occasions using a towed hydrophone array. Twenty-three clicks (including on and off-axis clicks) were extracted using an automated detector. Preliminary results show that this species produces clicks with a peak frequency of 131 kHz. More recordings are expected to be obtained next year. With the aim of distinguishing between the echolocation signals of the sympatric Commerson?s and Peale's dolphins, we used passive acoustic monitoring of these species in the South Atlantic region, and contributed to the phylogenetic categorization through acoustical data. Recordings were obtained using a single hydrophone in the area of Puerto Santa Cruz, Santa Cruz Province, Argentina. Near 3,000 clicks (on and off-axis) were extracted and analyzed. Preliminary results indicate that the peak frequency distribution shows a bimodal distribution, with values below and above 150kHz. There is a statistically significant difference in the ratio of peak frequency between Commerson?s dolphins echolocation clicks found by Reyes et al (2015) and those extracted in this study: 90.1% of clicks from Reyes et al (2015) had a peak frequency of less than 150kHz while 98.2% of our clicks had a peak frequency of less than 150kHz. This suggests that Peale?s dolphins were indeed recorded in Puerto Santa Cruz and that they produce NBHF clicks with peak frequency below 150kHz. More recordings will be conducted with the objective of gathering vocalizations of Peale?s dolphins in the absence of other species, such that we can properly characterize the echolocation signals produced by this species in the Southern South Atlantic.