Scientist discovers why seals do not drown while diving

A scientist from Northern Ireland has discovered the super sense that makes marine mammals the ultimate divers.

Dr Chris McKnight from County Antrim has been researching how seals can hold their breath much longer underwater than many other species as part of his work at the University of St Andrews in Scotland.

He found that, as well as being able to store oxygen efficiently, they have a unique ability to cognitively perceive levels in their blood so as to not run out and drown.

"To find such a fundamental aspect of the evolution of marine mammals that is so central to a huge part of what they do - dive - is incredibly exciting," Dr McKnight said.

He said the adaptation was "key" to the evolution of marine mammals like seals and walruses, allowing them and potentially other breath-hold diving animals, like birds and reptiles, to spend most of their lives without any access to air while diving.

"It feels like something that has been right under our nose all this time," Dr McKnight added.

"As simple and as logical as it might seem at face value, that seals can sense oxygen, and that this helps them to make decisions so they don't run out of oxygen and drown, evolutionarily it puts them and their physiology amongst some of the most uniquely adapted animals."

While scientists knew how the mammals could hold their breath for so long, they didn't know they judged the length of their dives.

To find out, six juvenile seals were studied at the university's Sea Mammal Research Unit for almost a year, testing how they adjusted their behaviour according to how much oxygen was available to them.

Seals like Trish and Oisin dived underwater of their own free will in the unit's pool to catch fish, while being observed.

The air mixes they were exposed to were altered to affect the levels of oxygen and carbon dioxide.

The duration of each dive was positively affected by the availability of oxygen, but carbon dioxide had no impact.

That showed the seals are not sensitive to carbon dioxide as other species may be.

Dr Joanna Kershaw, who co-authored the report, praised the talent and dedication of the research team.

"It's been so exciting to work with these amazing animals and uncover one of the fundamental reasons they're so perfectly adapted to their environment," she said.