Food reward in Bottlenose Dolphins (Tursiops truncatus) and Belugas Whales (Delphinapterus leucas) reduces heart rate and increase heart rate variability.

Authors

torrente, a. G., Bouchard, B., Perry, M., Pezzino, P., Arenarez, J., Gonzalez, A., Bonadonna, F., Campagna, S., Fahlman, A., Celerier, A.

Abstract

Heart rate (HR) and its variability (HRV), mediated by the autonomic nervous system are key indicators of diving physiology and behavioral state, in vertebrates. However, these indicators remain understudied in cetaceans due to the technical challenges of recording electrocardiograms (ECGs) underwater. To overcome these challenges, we developed a waterproof device based on an all-in-one suction-cup that integrate an ECG-accelerometer logger with bipolar electrodes. Using this device, we obtained high-resolution ECG signals in bottlenose dolphins (Tursiops truncatus, n=8), belugas (Delphinapterus leucas, n=2), and orcas (Orcinus orca, n=1) during breathing and apnea. This approach allowed us to highlight species-specific features of the ECG waveform, consistent with a biphasic T wave in the three species of cetaceans and a bifid P wave unique to belugas, which were independent from the respiration state. Resting surface HRs were 70 +/- 4 bpm in dolphins, 51 +/- 1 bpm in belugas, and 50 +/- 2 bpm in the orca and exhibited pronounced oscillation related to the mechanism of respiratory sinus arrhythmia. As expected, short apneas (~ 1 min) induced bradycardia in all three species (53 +/- 5, 33 +/- 3, and 37 +/- 2 bpm, respectively). In dolphins this bradycardia was coupled with a significant decrease of the coefficient of variability of RR intervals, one of the indices of HRV. Moreover, we were surprised to observe HR oscillations throughout apnea, suggesting a persistent fluctuation of autonomic modulation. Thus, to better understand autonomic modulation in cetaceans we employed food (fishes, squids, gelatin, etc.) as a strong rewarding stimulus. For that we compared HR and HRV during 2-min of food deprivation versus continuous feeding periods. In dolphins, food deprivation produced no significant change in HR or HRV from resting surface values, whereas continuous feeding decreased HR of about 20 % and increased HRV metrics (StDRR, CVRR, RMSSD). Belugas showed similar responses, with a HR decline of about 40 % and an increase HRV indices. These findings established baseline HR and HRV parameters during breathing or apnea for three cetacean species and demonstrate that autonomic responses to appetitive stimuli can be non-invasively quantified, validating a novel tool to investigate cetacean cardiovascular physiology and environmental perception.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 29 Jun 2026.

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