Variation in sperm whale (Physeter macrocephalus) coda vocalizations and social structure in the North Atlantic Ocean

Sperm whale--Behavior--North Atlantic Ocean;Sperm whale--Vocalization;Animal communication;Sound production by animals

Antunes, Ricardo ; Gordon, Jonathan ; Gordon, Jonathan

University:University of St Andrews

Department:Biology (School of)

关键词: Sperm whale--Behavior--North Atlantic Ocean;    Sperm whale--Vocalization;    Animal communication;    Sound production by animals;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/827/Ricardo%20Antunes%20PhD%20thesis.PDF?sequence=6&isAllowed=y

来源: DR-NTU

【 摘 要 】

This study aimed at complementing studies of sperm whale social and vocal behaviour thatwere restricted to the Pacific Ocean.The characteristic multi-pulsed structure of sperm whale clicks allows for estimation ofwhales' size from measurements of the inter-pulse intervals (IPI). I have developed two newautomatic methods for IPI estimation from clicks recorded during foraging dives. When comparedto other previously developed methods, the newly developed method that averages several clicks'autocorrelation function showed the best performance amongst the automatic methods.Previous studies did not support individual identity advertisement among social unitmembers as the function for the sperm whale communication signals called codas. I tested withincoda type variation for individual specific patterns and found that, while some coda types do notallow for individual discrimination, one did so. This variation suggests that different coda typesmay have distinct functions.Analysis of social structure in the Azores found that, similar to the Eastern Tropical Pacific,sperm whales form long term social units of about 12 individuals. Unlike the Pacific Ocean,Azorean social units do not form temporary groups with other units, suggesting differences in thecosts and benefits of group formation. I argue that these are due to differences in terms of predationpressure and intraspecific competition between the Azores and the Pacific study sites.The variation of coda repertoires in the Atlantic also showed a pattern dissimilar to thatpreviously documented in the Eastern Tropical Pacific. In the North Atlantic, coda repertoirevariation is mostly geographic, which is parsimoniously explained by random drift of culturallytransmitted coda repertoires. No sympatric vocal clans with distinct dialects were found as has beennoted in the Pacific. Drawing upon the differences found in social structure I argue that selection formaximization of differences between units with similar foraging strategies may have led to thePacific vocal clans.The differences between oceans suggest that sperm whales may adaptively adjust theirbehaviour according to experienced ecological conditions.