Background
Aim & Hypothesis
When marine mammals dive, they are exposed to repeated cycles of elevated pressure and limited oxygen supply, which trigger specific physiological responses, such as the dive response. The autonomic nervous system regulates this response, which helps extend aerobic dive duration and protects vital organs from hypoxia through a reduction in heart rate and peripheral vasoconstriction.
Multiple factors can influence marine mammals’ heart rate during diving, including volitional control, activity level, body mass, dive duration, and hydrostatic pressure.
It has been suggested that lung compression from increased dive depth and pressure reduces diving heart rate. Additionally, previous studies reported that longer dives are associated with lower heart rate, although they failed to separate the effect of depth from duration, as deeper dives tend to be longer.
This study investigated whether depth directly modulates the heart rate and heart rate variability (HRV) of common bottlenose dolphins (Tursiops truncatus) when accounting for breathing frequency and controlling for dive duration and activity. I hypothesized that increasing depth would decrease heart rate due to the physiological effects of pressure on lung volume.
