Decoding dolphin sounds to understand their behavior

Jim Crocker
5th December, 2025

Decoding dolphin sounds to understand their behavior

Positioning of the recording device (red circle) in the “Laguna dei delfini” pool (from study).

Image adapted from: Screpanti et al. / CC BY (Source)

Key Findings

  • This study, conducted in Italy, analyzed bottlenose dolphin vocalizations throughout a 24-hour period at Oltremare Marine Park to understand how activity influences their sounds
  • Dolphins vocalized significantly more during structured activities like training and feeding compared to unstructured rest periods, across all vocalization types
  • Play sessions triggered the highest rates of pulsed vocalizations, suggesting this activity strongly encourages social interaction and exploration through sound
Understanding dolphin communication is crucial for both conservation efforts and ensuring the wellbeing of dolphins in managed care. Bottlenose dolphins rely heavily on vocalizations for social interaction, foraging, and navigating their environment. Studying these sounds can reveal a great deal about their behaviour and needs. A recent study conducted by researchers from Università Politecnica delle Marche, National Research Council (CNR), Oltremare Marine Park, National Biodiversity Future Center, Università Politecnica delle Marche, and Jimma University College of Agriculture and Veterinary Medicine[1] investigated how bottlenose dolphin vocalizations change throughout a typical day in a marine park setting. The research focused on seven dolphins at Oltremare Marine Park in Italy. Over a 24-hour period, continuous acoustic recordings were made, capturing all sounds produced by the dolphins. These recordings were then meticulously analyzed to identify different types of vocalizations and correlate them with the dolphins’ activities – including training, feeding, play, and periods of unstructured time. The aim was to determine if specific activities prompted changes in the frequency or type of sounds the dolphins made. Dolphin vocalizations are complex. They include whistles, which are often used for individual recognition and maintaining contact, and pulsed sounds, which encompass a range of signals like echolocation clicks (used for sensing their surroundings), burst-pulse sounds (associated with social communication), and feeding buzzes (produced during hunting). Identifying and categorizing these sounds requires specialized software and careful manual review. In this study, researchers manually identified 3,111 whistles and used an automated algorithm to detect 1,277 pulsed vocalizations, classifying them based on characteristics like signal-to-noise ratio (SNR) – a measure of sound clarity – and the timing between clicks. The findings revealed a clear pattern: dolphins vocalized significantly more during structured activities, such as training and feeding, compared to unstructured periods. This increase was observed across all four vocalization types. Interestingly, play sessions triggered the highest rates of pulsed vocalizations. This suggests that play is a particularly stimulating activity, encouraging increased social interaction and exploration. This aligns with previous research[2] which demonstrated a strong correlation between activities and the types of vocalizations produced by dolphins, even in a zoological setting. The study builds upon earlier work that highlighted the diversity of dolphin vocalizations and their connection to various contexts[3][4]. For example, research has shown that whistle characteristics can vary depending on factors like group size, location, and even ambient noise levels[4]. The current study adds to this understanding by demonstrating how daily routines influence vocal behaviour in a controlled environment. Furthermore, the observation of increased pulsed vocalizations during play supports the idea that these sounds are linked to social and exploratory behaviours, as suggested by previous investigations[2]. The researchers also addressed the reliability of their data by analyzing the signal quality, ensuring that the sounds they were studying were clear and not obscured by background noise. Finally, recognizing the value of this data for future research, the complete annotated dataset has been made publicly available, allowing other scientists to further investigate dolphin bioacoustics and potentially develop artificial intelligence tools for acoustic monitoring. This open-access approach fosters collaboration and accelerates scientific discovery.

WildlifeAnimal ScienceMarine Biology

References

Main Study

1) Acoustic analysis of bottlenose dolphin vocalizations for behavioral classification in controlled settings

Published 3rd December, 2025

https://doi.org/10.1371/journal.pone.0336419

Related Studies

2) Vocal activities reflect the temporal distribution of bottlenose dolphin social and non-social activity in a zoological park.

https://doi.org/10.1002/zoo.21387

3) Vocal universals and geographic variations in the acoustic repertoire of the common bottlenose dolphin.

https://doi.org/10.1038/s41598-021-90710-9

4) Underwater recordings of the whistles of bottlenose dolphins in Fremantle Inner Harbour, Western Australia.

https://doi.org/10.1038/sdata.2017.126


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