A characterization of Guyana dolphin (Sotalia guianensis)whistles from Costa Rica: The importance of broadbandrecording systems

摘要

Knowledge of the whistle structure in Guyana dolphins comes mostly from Brazilian populationswhere recordings have been made using limited bandwidth systems (18 and 24 kHz). In Brazil,Guyana dolphin whistle frequency span is 1.34-23.89 kHz, but authors have suggested that limitsof their recording system may underestimate frequency span. Whistles of Guyana dolphins fromCosta Rica were studied using a broadband recording system. How bandwidth limitations affect theunderstanding of whistle structure and species classification between sympatric dolphin species wasevaluated. In addition, whistles were compared to Brazilian populations. Guyana dolphin whistlefrequency span was 1.38 up to 48.40 kHz, greater than previously reported. Bandwidth limitationsexplained 89% of the whistle variation between studies, and increase in bandwidth improved thewhistle classification of Guyana dolphins. Whistle duration and minimum frequency were the mostimportant variables in dolphin species classification. Finally, after accounting for differences inrecording systems, Costa Rican Guyana dolphins whistled with significantly higher frequency thanBrazilian populations, providing evidence for a postulated increase in frequency from south to north.The study concludes that equipment with an upper frequency limit of at least 50 kHz (150 kHz forharmonics) is required to capture the entire whistle repertoire of the Guyana dolphin.