Abstract
Dolphins exchange information with conspecifics using different types of vocalizations that are often associated with specific behaviors. The present study used simultaneous acoustic and video recordings of captive bottlenose dolphins (Tursiops truncatus) in Honduras to describe potential correlations between the type of mouthing behavior (open mouth, mouthing, bite) and associated vocalizations (whistle, whistle-squawk, chirp, moan, burst-pulse ‘A’, burst-pulse ‘B’, clicks). Literature on sound-behavior relationships among odontocetes with the noted infrequent systematic analyses of mouth actions highlights the need for this investigation. The influence of aggression on vocalization use was also addressed. From this observational study a series of general expectations on the interaction of sound, mouth action, and aggressive context are presented. Mouth actions are associated with vocalizations more often than not, and results suggest an overall flexible association of vocalizations during mouth actions, with the production of various sounds altered during aggressive contexts. There is an apparent distinction of frequency-modulated sounds with mouthing, suggesting that frequency parameters are an important characteristic of information exchange during mouth actions, and further that mouth actions are individually distinct behaviors. A dichotomy of burst pulse sounds in association with aggressive and non-aggressive contexts also introduces the need to analyze pulsed sounds according to inter-pulse interval. This paper proposes that there may be an interactive function to the use of vocalizations during mouth actions that is not yet understood.
Highlights
Title Vocalizations produced by bottlenose dolphins (Tursiops truncatus) during mouth actions in aggressive and non-aggressive contexts
A dichotomy of burst pulse sounds in association with aggressive and non-aggressive contexts introduces the need to analyze pulsed sounds according to inter-pulse interval
These ranges were defined by first determining the minimum and maximum inter-pulse interval (IPI), and dividing this total range in half; the lower IPIs were labeled as A and the higher IPIs were labeled as B. This was done to provide an unbiased distinction between burst-pulse vocalizations types based on their IPI, rather than their spectrogram appearance
Summary
Title Vocalizations produced by bottlenose dolphins (Tursiops truncatus) during mouth actions in aggressive and non-aggressive contexts. The present study used simultaneous acoustic and video recordings of captive bottlenose dolphins (Tursiops truncatus) in Honduras to describe potential correlations between the type of mouth actions (open mouth, mouthing, bite) and associated vocalizations (whistle, whistle squawk, chirp, moan, burst-pulse A, burst-pulse B, clicks). The influence of aggression on vocalization use was addressed From this observational study a series of general expectations on the interaction of sound, mouth action, and aggressive context are presented. Bottlenose dolphin (Tursiops truncatus) vocalizations are among the most studied (Tyack & Clark, 2000) and include a variety of vocalizations with differing parameters (Janik, 2009). It is evident from the literature that behavioral context plays a role in the type of vocalizations emitted by dolphins; few studies have examined the relationship between mouth action and vocalization production. There will be a difference in the vocalizations produced during all mouth actions dependent upon the aggressive context of the mouth "!
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