The tale of Cuvier’s whales--nature’s marathon divers

Shreya Dube discusses the breathtaking diving power of Cuvier's beaked whale.

Shreya Dube
12th November 2020
Size comparison between Cuvier's beaked whale and human diver
Cuvier’s beaked whales are a powerhouse of record holders and a feat of animal physiology amongst their oceanic peers. Their latest biological marvel is an astonishing dive record of 222 minutes, smashing the previous record set in 2014 (by the same species nonetheless)  for the longest mammalian dive of 137.5 minutes. Not only this but they also hold the record of the deepest divers too with a record at 2992m. These records defy logic as there are a myriad of issues associated with deep diving such as a lack of oxygen or pressure which at just 1000m is 100 times greater than the surface pressure. Dear reader, let us dive into the minutiae of these marine powerhouses. 

Cuvier’s beaked whales have a barrage of physiological adaptations linked to their performance, such as the ability to fold their rib cage as to decrease buoyancy, reduce the size of an air pocket (in their lungs) and raise their tail flukes to dive deeper. Another way they achieve the same effect is by exhaling up to 90% of their total lung capacity prior to diving and in some deep dives forgoing breathing altogether, along with shunting blood from their extremities to their heart and brain. The shutting down of peristalsis, renal and hepatic function as well as acidic blood (due to a buildup of lactic acid) is the consequence of this shunting. This begs the question, how are their respiring tissues getting enough oxygen? The answer to this lies in the molecule myoglobin--an oxygen storage molecule. Myoglobin is similar to haemoglobin (our oxygen storage molecule found in red blood cells), but it has a very high affinity meaning it can readily dissociate its oxygen to muscles that need it. Normally myoglobin is a negatively charged molecule and as we know--opposites attract. In humans an abundance of myoglobin leads to diseases such as diabetes and Alzheimer's, but Cuvier’s Beaked Whales have another trick betwixt their fins--their myoglobin is negatively charged and repels so there is no aggregation. 

Where Cuvier's beaked whale can be found

Image Credit: Wikimedia Commons

To put it into context, the longest human freedive was set in 2016 by Aleix Segura at a staggering 24 minutes and 3 seconds.

As you can see there are similarities and differences between us and our ocean-dwelling mammalian record breakers. To put it into context, the longest human freedive was set in 2016 by Aleix Segura at a staggering 24 minutes and 3 seconds.  Freedivers such as James Nestor in an interview with National Geographic give us an insight into how humans can achieve this:

“Our heart rates lower about 25 percent. Blood begins rushing from our extremities into the core. The mind enters a meditative state. At around 250 to 300 feet the heart rate of some of these free divers has been recorded to be about 14 beats per minute. That’s about a third of a coma patient’s. It should support consciousness, according to physiologists. And yet deep in the ocean it does. But no one knows exactly how.”

Whilst studying animals can be rewarding, we must remember to do it ethically.

There is one concerning thing though--human interference. The record-breaking dive times, whilst impressive, are not typical nor are they an indicator of typical behaviour. One study shows the atypical responses of beaked whales in response to military sonar. They found that the whales stopped fluking and echolocating and swam away rapidly and silently, then stayed underwater for longer as a response; to put it into comparison typical Cuvier’s Beaked Whale dives are roughly an hour and 1000-2000m. More worrying still, it was previously thought that beaked whales couldn’t get decompression sickness or “the bends” but studies show that they indeed can and a cause being from retreating rapidly and incorrectly from sonar interference. Whilst studying animals can be rewarding, we must remember to do it ethically. 

So should we hold our breath for a new diving record? We’re seemingly always pushing the limits of physiology- both human and animal alike. Dear reader, only time can tell.

Featured Image: Wikimedia Commons

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