Influence of Positive Affect on Burst Pulse Vocalization in Bottlenose Dolphins (Tursiops truncatus)

Author

• Joclyn Destiny Villegas, University of South AlabamaFollow

Date of Award

5-2026

Document Type

Dissertation

Degree Name

Ph.D.

Department

Marine Sciences

Committee Chair

Heidi Lyn, Ph.D.

Abstract

This dissertation examined how positive affect influences burst pulse vocal behavior in bottlenose dolphins and developed tools to improve the study of these signals. In Chapter II, I designed and tested a small, portable three-element hydrophone array and a machine-learning detector specialized for burst pulses. The hydrophone array successfully localized whistles and burst pulses to a target lagoon, demonstrating utility for lagoon-level acoustic localization, although individual-level assignment remained inconsistent. The detector showed moderate precision but low recall, indicating promise for automated screening while also showing that larger and more diverse annotated datasets are needed to improve burst pulse detection.

In Chapters III and IV, I investigated whether specific burst pulse subtypes, defined by modulation patterns in their click repetition rates, were associated with positive and social contexts in dolphins living in professional care. Using a tractable subtype classification system, I found that burst pulse subtypes with increasing click repetition rate onsets, particularly the Increasing and Up-Down subtypes, were associated with positive contexts across both off-session and on-session phases. During off-session positive interventions, burst pulses comprised a greater share of post-interaction vocalizations than pre-interaction vocalizations, and the Increasing subtype significantly occurred after interactions. During on-session training, energetic output did not explain overall vocal type production, indicating that vocal behavior was shaped more by behavioral context and outcome than by physical exertion alone. A variant of the Up-Down subtype, termed “Scream: Up-Down”, occurred most often after a trainer’s bridge and was strongly associated with social reinforcement. Under high intensity social reinforcement, dolphins sharply increased repetition of Scream: Up-Down vocalizations. Trainers did not preferentially deliver fish following any particular burst pulse subtype or variant, suggesting that these vocalizations are unlikely to function primarily as signals for obtaining fish and instead may reflect positive affect following successful behavior and social engagement.

Overall, this dissertation shows that fine-scale burst pulse structure can provide meaningful information about affective and social context in bottlenose dolphins. These findings advance efforts to identify candidate acoustic indicators of positive welfare, provide practical tools for studying dolphin communication, and contribute to a broader understanding of sound as a flexible medium for affective and social expression. As marine soundscapes continue to change under increasing human influence, understanding which vocal features carry social and affective significance will be increasingly important for interpreting how dolphins maintain communication in altered acoustic environments.

Recommended Citation

Villegas, Joclyn Destiny, "Influence of Positive Affect on Burst Pulse Vocalization in Bottlenose Dolphins (Tursiops truncatus)" (2026). Graduate Theses and Dissertations (2019 - present). 255.
https://jagworks.southalabama.edu/theses_diss/255