Captive Bottlenose Dolphins Change Their Vocalizations During Enrichment Activities, New Study Finds
Dolphins are well known for their complex sounds, but a new scientific study suggests that these vocalizations change in clear and measurable ways when dolphins take part in structured activities such as training, feeding, and play. Research published in PLOS One shows that captive bottlenose dolphins do not vocalize randomly throughout the day. Instead, their sounds appear closely linked to how engaged and stimulated they are during specific activities.
The study was carried out by Francesco Di Nardo of Università Politecnica delle Marche in Ancona, Italy, along with an international team of researchers. Their work focused on understanding whether dolphin vocal behavior could be used as an indicator of motivation, engagement, and overall welfare in controlled environments.
Why Dolphin Vocalizations Matter
Dolphins rely heavily on sound to navigate their world. They produce a wide range of vocalizations that serve different purposes, including echolocation, social communication, and coordination within groups. These sounds vary depending on social context, environmental conditions, and external stimuli. Because of this, vocal behavior is often viewed as a window into dolphin cognition and emotional states.
In captivity, dolphins are provided with enrichment activities to maintain physical and mental well-being. However, determining which activities are truly engaging for dolphins remains a challenge. The researchers behind this study aimed to explore whether changes in dolphin vocal patterns could offer measurable insight into how dolphins respond to structured activities.
Study Location and Subjects
The research took place at Oltremare Marine Park in Riccione, Italy, a facility that houses bottlenose dolphins under human care. The study focused on seven bottlenose dolphins (Tursiops truncatus), consisting of two males and five females.
The researchers conducted continuous acoustic monitoring over a 24-hour period in 2021. During this time, they also carefully documented the dolphins’ daily routine, which included feeding sessions, trainer-led exercises, play interactions, and periods with no organized activity.
How the Research Was Conducted
To capture dolphin vocal behavior, underwater recording devices were positioned in the pool, including a hydrophone placed at a fixed location to ensure consistent data collection. The researchers recorded all sounds produced by the dolphins throughout the day and night.
Once the recordings were collected, the team performed detailed acoustic analyses. Dolphin sounds were classified into two major categories:
- Whistles, typically associated with social communication
- Pulsed sounds, which include clicks, burst-pulse sounds, and other rapid acoustic signals
The researchers quantified each vocalization by measuring its frequency, duration, number, and diversity. They then compared vocal activity during periods of organized enrichment with periods when no structured activities were taking place.
Key Findings From the Study
The results revealed a clear and consistent pattern. Organized activities strongly influenced dolphin vocal behavior. During structured periods such as training sessions, feeding, and play, dolphins produced more vocalizations across all sound types.
Both whistles and pulsed sounds increased in number and duration during these activities. This suggests heightened motivation, increased social interaction, and greater engagement with both fellow dolphins and human trainers.
In contrast, periods without organized activity were associated with reduced vocal output. Dolphins still vocalized during these times, but their acoustic activity was noticeably lower.
The findings indicate that dolphin vocalizations are not just background noise but reflect meaningful behavioral and emotional states.
What This Means for Dolphin Welfare
One of the most important implications of this research lies in animal welfare management. The study suggests that monitoring vocal patterns could help caretakers assess how dolphins respond to different enrichment programs.
If certain activities consistently trigger higher levels of vocal engagement, those activities may be more stimulating and rewarding for dolphins. Over time, this information could be used to refine enrichment strategies and improve living conditions for dolphins in managed care.
The researchers emphasize that understanding how dolphins adjust their vocal behavior throughout the day provides valuable insight into their social dynamics and emotional engagement.
Study Limitations and Future Research
While the findings are compelling, the authors acknowledge several limitations. The study involved a relatively small sample size of seven dolphins and was conducted over a single day. These factors limit how broadly the results can be generalized.
Future studies could expand on this work by observing larger groups of dolphins, extending recording periods, and comparing different types of enrichment activities rather than simply contrasting activity versus inactivity. Researchers also suggest examining how environmental variables and group composition influence vocal behavior.
Despite these limitations, the study provides a strong foundation for future research into dolphin communication and welfare assessment.
The Importance of Open Acoustic Data
An important contribution of this research is the release of the full dolphin vocalization dataset. By making these recordings publicly available, the authors hope to encourage further studies in marine bioacoustics, animal behavior, and conservation science.
Open datasets allow researchers worldwide to reanalyze sounds, develop new classification methods, and explore questions beyond the scope of the original study. This approach reflects a growing emphasis on transparency and collaboration in scientific research.
Understanding Dolphin Sounds Beyond This Study
Bottlenose dolphins are among the most extensively studied marine mammals, yet many aspects of their communication remain poorly understood. Dolphins are known to use signature whistles, which function as unique acoustic identifiers for individuals. They also produce complex pulsed sounds during social interactions, play, and coordinated behaviors.
Research like this adds to a growing body of evidence that dolphin vocalizations are highly flexible and context-dependent. It also reinforces the idea that sound plays a central role in dolphin social life, even in captive environments.
Why This Research Matters
This study highlights how careful acoustic monitoring can serve as a powerful, non-invasive tool for understanding dolphin behavior. By linking vocal patterns to specific activities, researchers and caretakers gain a clearer picture of what engages dolphins and how enrichment programs affect them.
Beyond captivity, these findings may also help scientists better interpret dolphin vocalizations in the wild, where social context and environmental complexity are even greater.
Ultimately, the research underscores the idea that dolphins are highly responsive, socially aware animals whose voices reflect their experiences throughout the day.
Research Paper:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0336419
