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Dolphins actively slow their hearts before diving and can even adjust their heart rate depending on how long they intend to dive, suggests a new study. Posted in Frontiers in physiology, the findings provide new insights into how marine mammals conserve oxygen and adapt to pressure when diving.
The authors worked with three male bottlenose dolphins (Tursiops truncatus), specially trained to hold their breath for different periods of time under instruction. “We trained dolphins to hold their breath long, short and where they could do whatever they want,” explains Dr. Andreas Fahlman of the Fundación Oceanogràfic, Valencia, Spain. “When asked to hold their breath, their heart rate dropped before or immediately when they started freediving. We also observed that dolphins lowered their heart rate faster and faster while preparing for freediving. long, compared to the other sockets “.
The findings reveal that dolphins, and possibly other marine mammals, can consciously alter their heart rate to match the planned dive duration. “Dolphins have the ability to vary their heart rate reduction as much as you and I can reduce the rate at which we breathe,” suggests Fahlman. “This allows them to conserve oxygen during their dives and may also be the key to avoiding diving-related problems such as decompression sickness, known as ‘bends’.”
Understanding how marine mammals are able to dive safely for extended periods of time is critical to mitigating the health impacts of human-made sound disturbances on marine mammals. “Human-made sounds, such as underwater explosions during oil exploration, are linked to problems like the ‘curves’ in these animals,” continues Fahlman. “If this ability to regulate heart rate is important in avoiding decompression sickness and sudden exposure to unusual sound causes this mechanism to fail, we should avoid sudden loud disturbances and instead slowly increase the noise level over time to cause minimal stress. In other words, our research could provide very simple mitigation methods to allow humans and animals to safely share the ocean. “
The practical challenges of measuring a dolphin’s physiological functions, such as heart rate and respiration, have previously prevented scientists from fully understanding the changes in their physiology while diving. “We worked with a small sample of three trained male dolphins housed in professional care,” says Fahlman. “We used bespoke equipment to measure the animals’ lung function and connected electrocardiographic (ECG) sensors to measure their heart rate.”
“The close relationship between trainers and animals is extremely important when training dolphins to participate in scientific studies,” explains Andy Jabas, Dolphin Care Specialist at Siegfried & Roy’s Secret Garden and Dolphin Habitat at the Mirage, Las Vegas, USA , home to the dolphins they studied here. “This bond of trust has allowed us to have a safe environment for the dolphins to familiarize themselves with specialized equipment and to learn freediving in a fun and challenging training environment. The dolphins have all enjoyed participating in the study and have been able to leave at any time “.
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