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- Vocal universals and geographic variations in the acoustic repertoire of the common bottlenose dolphinPublication . Luís, A. R.; May-Collado, L. J.; Rako-Gospić, N.; Gridley, T.; Papale, E.; Azevedo, A.; Silva, M. A.; Buscaino, G.; Herzing, D.; dos Santos, M. E.Acoustical geographic variation is common in widely distributed species and it is already described for several taxa, at various scales. In cetaceans, intraspecific variation in acoustic repertoires has been linked to ecological factors, geographical barriers, and social processes. For the common bottlenose dolphin (Tursiops truncatus), studies on acoustic variability are scarce, focus on a single signal type-whistles and on the influence of environmental variables. Here, we analyze the acoustic emissions of nine bottlenose dolphin populations across the Atlantic Ocean and the Mediterranean Sea, and identify common signal types and acoustic variants to assess repertoires' (dis)similarity. Overall, these dolphins present a rich acoustic repertoire, with 24 distinct signal sub-types including: whistles, burst-pulsed sounds, brays and bangs. Acoustic divergence was observed only in social signals, suggesting the relevance of cultural transmission in geographic variation. The repertoire dissimilarity values were remarkably low (from 0.08 to 0.4) and do not reflect the geographic distances among populations. Our findings suggest that acoustic ecology may play an important role in the occurrence of intraspecific variability, as proposed by the 'environmental adaptation hypothesis'. Further work may clarify the boundaries between neighboring populations, and shed light into vocal learning and cultural transmission in bottlenose dolphin societies.
- Changes in the acoustic behavior of resident bottlenose dolphins near operating vesselsPublication . Luís, Ana Rita; Couchinho, Miguel N.; Santos, Manuel Eduardo dosPublished for the Society for Marine Mammalogy, Marine Mammal Science is a source of significant new findings on marine mammals resulting from original research on their form and function, evolution, systematics, physiology, biochemistry, behavior, population biology, life history, genetics, ecology and conservation. The journal features both original and review articles, notes, opinions and letters. It serves as a vital resource for anyone studying marine mammals.
- Signature whistles in wild bottlenose dolphins : long-term stability and emission ratesPublication . Luís, A. R.; Couchinho, Miguel N.; Santos, Manuel Eduardo dosWhistles are key elements in the acoustic repertoire of bottlenose dolphins. In this species, the frequency contours of whistles are used as individual signatures. Assessing the long-lasting stability of such stereotyped signals, and the abundant production of non-stereotyped whistles in the wild, is relevant to a more complete understanding of their biological function. Additionally, studying the effects of group size and activity patterns on whistle emission rate may provide insights into the use of these calls. In this study, we document the decades-long occurrence of whistles with stereotyped frequency contours in a population of wild bottlenose dolphins, resident in the region of the Sado estuary, Portugal. Confirmed stereotypy throughout more than 20 years, and positive identification using the signature identification (SIGID) criteria, suggests that the identified stereotyped whistles are in fact signature whistles. The potential roles of non-stereotyped whistles, which represent 68 % of all whistles recorded, are still unclear and should be further investigated. Emission rates were significantly higher during food-related events. Finally, our data show a comparatively high overall whistle production for this population, and no positive correlation between group size and emission rates, suggesting social or environmental restriction mechanisms in vocal production.