EurekAlert recently reported that dolphins actively prevent dive related problems like the bends by conserving oxygen and decreasing their heart rate before diving. 

A recent study, published in Frontiers in Physiology, suggests that dolphins can adjust their heart rates depending on the planned length of each dive. The findings provide clues to how dolphins conserve oxygen and adapt to pressure when diving. 

Researchers trained bottlenose dolphins to perform various breath holds on command – one short, one long, and one where the dolphins themselves could choose the duration. The team then used custom-made equipment to assess the animals’ lung function and electrocardiogram sensors to monitor their heart rates.

"When asked to hold their breath, their heart rates lowered before or immediately as they began the breath-hold. We also observed that the dolphins reduced their heart rates faster and further when preparing for the long breath-hold, compared to the other holds,"- Dr Andreas Fahlman, Fundación Oceanogràfic, Spain.

This suggests that dolphins - and maybe other marine mammals - deliberately alter their heart rate based on each individual dive. Fahlman believes “this allows them to conserve oxygen during their dives, and may also be key to avoiding diving-related problems such as decompression sickness, known as ‘the bends’."

Research such as this could help provide insights into the impacts of man-made sounds on marine mammals. Loud noises like those produced during underwater oil exploration have been linked with decompression sickness in marine mammals. "If this ability to regulate heart rate is important to avoid decompression sickness, and sudden exposure to an 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", continued Fahlman.

How dolphins avoid the bends
How dolphins avoid the bends

While this research might sound a little intrusive, the team at Siegfried & Roy's Secret Garden and Dolphin Habitat at the Mirage, Las Vegas, where the dolphins are kept, ensured they were free to leave at any time. "This bond of trust enabled us to have a safe environment for the dolphins to become familiar with the specialised equipment and to learn to perform the breath-holds in a fun and stimulating training environment,” explained Andy Jabas, one of the Dolphin Care Specialists.