Do dolphins rehearse shows when at rest? Evidence from vocal copying

International audienceIt is known that delphinidae can associate heard sounds with salient events/objects and mimic these sounds, mostly in the corresponding context. Thus, one can wonder whether dolphins, as other animals and humans, have a sort of sensory memory of events. Here we show that a group of five bottlenose dolphins in the Planète Sauvage dolphinarium (France) produced, during their nighttime resting periods, non-dolphin sounds that they heard during performance shows. In total, 3246 vocalizations were recorded during >120 hours (2588 vocalizations during >100 hours at day, 658 vocalizations during >20 hours at night). Generally in the middle of the night, these animals produced vocal copies of whale sounds that had been broadcast during daily shows. Recordings made before the whale sounds started being broadcast revealed that they have never emitted such sounds before. These unusual vocalizations differ from all other sounds in the dolphins repertoire. The similarity between the dolphins copies and the model whale sounds was substantiated by a discriminant function analysis with measured acoustic parameters and a playback experiment with human audience. This is to our knowledge the first evidence for the production of sounds heard during day salient events in a nocturnal resting context in marine mammals

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Visual laterality in dolphins: importance of the familiarity of stimuli

<p>Abstract</p> <p>Background</p> <p>Many studies of cerebral asymmetries in different species lead, on the one hand, to a better understanding of the functions of each cerebral hemisphere and, on the other hand, to develop an evolutionary history of hemispheric laterality. Our animal model is particularly interesting because of its original evolutionary path, i.e. return to aquatic life after a terrestrial phase. The rare reports concerning visual laterality of marine mammals investigated mainly discrimination processes. As dolphins are migrant species they are confronted to a changing environment. Being able to categorize new versus familiar objects would allow dolphins a rapid adaptation to novel environments. Visual laterality could be a prerequisite to this adaptability. To date, no study, to our knowledge, has analyzed the environmental factors that could influence their visual laterality.</p> <p>Results</p> <p>We investigated visual laterality expressed spontaneously at the water surface by a group of five common bottlenose dolphins (<it>Tursiops truncatus</it>) in response to various stimuli. The stimuli presented ranged from very familiar objects (known and manipulated previously) to familiar objects (known but never manipulated) to unfamiliar objects (unknown, never seen previously). At the group level, dolphins used their left eye to observe very familiar objects and their right eye to observe unfamiliar objects. However, eyes are used indifferently to observe familiar objects with intermediate valence.</p> <p>Conclusion</p> <p>Our results suggest different visual cerebral processes based either on the global shape of well-known objects or on local details of unknown objects. Moreover, the manipulation of an object appears necessary for these dolphins to construct a global representation of an object enabling its immediate categorization for subsequent use. Our experimental results pointed out some cognitive capacities of dolphins which might be crucial for their wild life given their fission-fusion social system and migratory behaviour.</p

Visual laterality in dolphins when looking at (un)familiar humans

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Consequences of a group formation on bottlenose dolphins’ vocal repertoires

International audienceThere is evidence of changes in the vocal structure of song birds and monkey calls in responseto modifications of the social group composition. Nevertheless, the rapidity and significanceof such changes has been rarely investigated. In the present study, we investigated the vocalresponses of captive bottlenose dolphins (Tursiops truncatus) to strong modifications of theirenvironmental and social situation. We followed individuals (3 males and 2 females)originating from 2 different and distant groups before and after their grouping, as well asduring capture. Clear differences occurred between the pre- and post-grouping contexts withchanges in whistle repertoires as revealed by the emergence of new whistle types. Moreover,the capture appeared as a very particular situation. First, whistle types that were not foundbefore and after capture appeared in that context. Second, even common whistle types thatwere produced in all contexts, showed changes in their acoustic structure at the time ofcapture (8 of 11 parameters measured). Vocal changes may therefore be reliable indications ofstress. These results suggest new lines of research about the significance of vocal changes toevaluate animal states and social bonds’ creation

Nocturnal vocal activity in captive bottlenose dolphins (Tursiops truncatus): could dolphins have presleep choruses?

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Study of repertoire use reveals unexpected context-dependent vocalizations in bottlenose dolphins (Tursiops truncatus)

International audienceDolphins are known for their complex vocal communication, not least because of their capacity for acoustic plasticity. Paradoxically, we know little about their capacity for flexible vocal use. The difficulty in describing the behaviours performed underwater while vocalizing makes it difficult to analyse the contexts of emissions. Dolphins&#039; main vocal categories are typically considered to be used for scanning the environment (clicks), agonistic encounters (burst pulses) and socio-affiliative interactions (whistles). Dolphins can also combine these categories in mixed vocal emissions, whose use remains unclear. To better understand how vocalizations are used, we simultaneously recorded vocal production and the associated behaviours by conducting underwater observations (N = 479 events) on a group of 7 bottlenose dolphins under human care. Our results showed a non-random association between vocal categories and behavioural contexts. Precisely, clicks were preferentially emitted during affiliative interactions and not during other social/solitary contexts, supporting a possible complementary communicative function. Burst pulses were associated to high arousal contexts (agonistic and social play), pinpointing on their use as an &quot;emotively charged&quot; signal. Whistles were related to solitary swimming and not preferentially produced in any social context. This questions whistles&#039; functions and supports their potential role as a distant contact call. Finally, mixed vocalizations were especially found associated with sexual (bust pulse-whistle-click), solitary play (burst pulse-whistle) and affiliative (click-whistle) behaviours. Depending on the case, their emission seems to confirm, modify or refine the functions of their simple counterparts. These results open up new avenues of research into the contextual use of dolphin acoustic signals

Behavioural evidence of magnetoreception in dolphin: Detection of experimental magnetic fields

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Do dolphins rehearse show-stimuli when at rest? Delayed matching of auditory memory

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