Feasibility of heart rate variability analysis for welfare assessment in dolphins: a preliminary report

This is a Preprint and has not been peer reviewed. This is version 6 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 6 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Monitoring stress and emotional states in dolphins is an important step toward improving animal welfare in managed care. Established physiological approaches, such as measuring cortisol from blood or fecal samples, have provided valuable information for stress assessment. Suction-based devices have also enabled cardiac monitoring, contributing to our understanding of diving physiology and circulatory control. Each of these methods offers unique strengths, but they may not always be suited for real-time or continuous monitoring during routine conditions. In this study, we propose a framework in which heart rate variability (HRV) serves as a non-invasive indicator of autonomic activity, stress, and emotional states. As an initial step, we tested the feasibility of attaching a commercially available belt-type heart rate monitor to dolphins. The device was fitted safely and generally tolerated, although subtle behavioral resistance was observed in some cases. In principle, this HRV-based framework is not limited to the belt-type device tested here and could be adapted to other attachment methods, provided stable cardiac signals are obtained. Continuous cardiac signal acquisition and HRV analysis are ongoing, but these preliminary results represent a first step toward introducing HRV-based welfare assessment in cetaceans. Importantly, the feasibility of this approach under routine husbandry conditions supports the development of practical, physiology-based welfare indicators that can be implemented on site by animal care staff. This framework has the potential to extend beyond dolphins to other marine mammals such as pinnipeds and sirenians, thereby contributing to the establishment of practical, non-invasive welfare assessment standards for zoos and aquaria. https://doi.org/10.32942/X20H15 Life Sciences, Social and Behavioral Sciences Dolphins, heart rate variability, HRV, animal welfare, stress assessment, marine mammals, Autonomic Nervous System, non-invasive monitoring, zoo and aquarium Published: 2025-09-24 16:57 Last Updated: 2026-03-31 14:47 - Version 5 - 2026-02-09 - Version 4 - 2025-10-21 - Version 3 - 2025-10-21 - Version 2 - 2025-09-24 - Version 1 - 2025-09-24 CC BY Attribution 4.0 International Conflict of interest statement: None Data and Code Availability Statement: No datasets or code are associated with this preprint. Language: English