Tuesday , January 26 2021

How dolphins avoid “curves”

Newswise – Dolphins are actively slowing their heart before diving and may even adjust their heart rate depending on how long they plan to dive, new research suggests. Posted in Limits in physiology, the findings provide new insights into how marine mammals save oxygen and adapt to pressure as they dive.

The authors worked with three male bottlenose dolphins (Tursiops truncatus), specially trained to hold their breath for varying times according to instructions. “We trained dolphins to hold their breath for a long time, short and where they could do whatever they wanted,” explains Dr. Andreas Falman of the Fundación Oceanogràfic, Valencia, Spain. “When asked to hold their breath, their heart rate dropped before or just when they started holding their breath. We also noticed that dolphins dropped their heart rate faster and further as they prepared for longer breaths, compared to the others “

The results reveal that dolphins, and possibly other marine mammals, can consciously change their heart rate to suit the length of their planned dive. “Dolphins have the capacity to change their heart rate reduction as much as you and I are able to reduce how fast we breathe,” Falman suggests. “This allows them to save oxygen while diving, and can also be crucial to avoid diving-related problems such as decompression sickness, known as ‘curves.’

Understanding how marine mammals are able to dive safely for long periods of time is crucial to mitigating the health effects of artificial sound disturbance on marine mammals. “Human-made noises, such as explosions underwater during oil exploration, are associated with problems such as ‘curves’ in these animals,” Falman continues. “If this ability to regulate heart rate is important to avoid 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. “In time to cause minimal stress. In other words, our research can provide very simple mitigation methods to enable 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 during diving. “We worked with a small sample size of three trained male dolphins placed in professional care,” explains Falman. “We used tailor-made equipment to measure lung function in animals and attached electrocardiogram (ECG) sensors to measure heart rate.”

“The close relationship between trainers and animals is extremely important when training dolphins to participate in scientific studies,” explains Andy Abbas, Siegfried’s Secret Garden Dolphin Care Specialist, and Roy and Dolphin Habitat in Mirage, Las Vegas, USA. dolphins studied here. “This relationship of trust has allowed us to have a safe environment for dolphins to become familiar with specialized equipment and learn to breathe in a fun and stimulating training environment. The dolphins all volunteered to study and were able to leave at any time.” .


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