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Bottlenose dolphins use whistles to communicate with their conspecifics and maintain group cohesion. We recorded 477 whistles of Indo-Pacific bottlenose dolphins ( Tursiops aduncus) in the Fremantle Inner Harbour, Western Australia, on nine occasions over a six-week period during May/June 2013. Over half (57 %) of the whistles had complex contours exhibiting at least one local extremum, while 32 % were straight upsweeps, 5 % downsweeps and 6 % constant-frequency. About 60 % of whistles occurred in trains. Fundamental frequency ranged from 1.1 to 18.4 kHz and whistle duration from 0.05 to 1.15 s. The maximum numbers of local extrema and inflection points were 7 and 9, respectively. Whistle parameters compared well to those of measurements made from other T. aduncus populations around Australia. Observed differences might be due to ambient noise rather than geographic separation. [ABSTRACT FROM AUTHOR]

Food-related signalling is widespread in the animal kingdom with some food-associated vocalizations considered functionally referential. Food calls can, however, vary greatly in the type of information they convey. Thus, there are a multitude of purposes for which food calls are used, including social recruitment, caller spacing, the indication of type, quantity, quality, divisibility of food, the caller's hunger level and even as tools to manipulate prey behaviour. Yet little work has focused on the social aspect of food calling in animals. We investigated the association of social signals in wild bottlenose dolphins with foraging behaviour where context-specific food-associated calls are commonly produced. Our data showed that specific social signals were significantly correlated with food call production and these calls rarely occurred in the absence of food calls. We suggest that animals are sharing additional information on the food patch itself with their social affiliates. [ABSTRACT FROM AUTHOR]

Two recent papers by Kuczaj et al. (Anim Cognit 18:543-550, 2015) and Eskelinen et al. (Anim Cognit 19:789-797, 2016) claim to have demonstrated that (i) bottlenose dolphins ( Tursiops truncatus) cooperated to solve a novel task and (ii) vocal signals were important for coordinating these cooperative efforts. Although it is likely that bottlenose dolphins may share communicative signals in order to achieve a common goal, we suggest that this has not been demonstrated in the aforementioned studies. Here, we discuss the two main problems that preclude any definitive conclusions being drawn on cooperative task success and vocal communication from these studies. The first lies in the experimental design. The 'cooperative task', involving an apparatus that requires two dolphins to pull in opposite directions in order to achieve a food reward, is not conducive to cooperation, but could instead reflect a competitive 'tug-of-war'. It is therefore of questionable use in distinguishing competitive from cooperative interactions. Second, the suggestion that the occurrence of burst-pulsed signals in this task was indicative of cooperation is disputable, as (i) this study could not determine which dolphins were actually producing the signals and (ii) this sound type is more commonly associated with aggressive signalling in dolphins. We commend the authors for investigating this exciting and topical area in animal communication and cognition, but the question of whether dolphins cooperate and communicate to solve a cooperative task remains as yet unanswered. [ABSTRACT FROM AUTHOR]