How dolphins avoid “the turns”

Dolphins actively slow their hearts before diving and can even adjust their heart rate depending on how long they plan to dive, a new study suggests. Published in Frontiers in Physiologythe findings provide new insights into how marine mammals conserve oxygen and adapt to pressure while diving.

The authors worked with three male bottlenose dolphins (Tursiops truncatus), specially trained to hold their breath on instruction for different time periods. “We trained the dolphins to take a long breath, a short one, and one where they could do whatever they wanted,” explains Dr. Andreas Fahlman of Fundación Oceanogràfic, Valencia, Spain. “When asked to hold their breath, their heart rate dropped before or immediately when they started to hold their breath. We also saw the dolphins lower their heart rate faster and further while preparing for the long breath hold, compared to the other attitudes. “.

The results show that dolphins, and possibly other marine mammals, can consciously adjust their heart rate to the length of their planned dive. “Dolphins have the ability to vary their lowering of the heart rate as much as you and I can reduce how fast we breathe,” said Fahlman. “This allows them to conserve oxygen during their dives, and it may also be key to avoiding dive-related problems such as decompression sickness, also known as” the turns.

Understanding how marine mammals can dive safely for a long time is crucial to mitigate the health effects of human-induced noise disturbances on marine mammals. “Man-made noises, such as underwater explosions during oil exploration, are linked to problems such as” the bends “in these animals,” Fahlman continued. “If this ability to regulate heart rate is important to prevent decompression sickness, and sudden exposure to an unusual sound causes this mechanism to fail, we should avoid sudden loud disturbances and instead increase the sound level slowly to cause minimal stress. words, our research can provide very simple mitigating methods to enable humans and animals to share the ocean safely ”.

The practical challenges of measuring a dolphin’s physiological functions, such as heart rate and respiration, previously prevented scientists from fully understanding changes in their physiology while diving. “We worked with a small sample of three trained male dolphins housed in professional care,” explains Fahlman. “We used custom equipment to measure the animals’ lung function, and attached electrocardiogram (ECG) sensors to measure their heart rate.”

“The close relationship between the trainers and the animals is extremely important in 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, United States, out. the dolphins studied here. “This bond of trust allowed us to have a safe environment for the dolphins to become familiar with the specialized equipment and to learn how to hold their breath in a fun and stimulating training environment. The dolphins all willingly participated in the study and were able to leave at any time ”.


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