A little-known and shy whale surprised scientists by staying submerged for nearly four hours.
Cuvier’s beaked whales are known for their deep diving abilities and they are on average about an hour underwater.
But the researchers were stunned when they recorded an animal diving for three hours and 42 minutes.
They believe this is the longest dive on record for a whale and almost certainly a record for all mammals.
Species of beaked whales are a bit of a mystery to scientists, who spend much of their time away from the coast.
The Cuvier’s Beaked Whale has a sturdy body, a small sloping head and a short beak. Males appear to have two teeth which they use for fighting, females do not appear to have any.
They normally hunt squid for food, usually sucking the creatures into their mouths to eat them.
Scientists say that by chasing their favorite food, these whales have been documented diving to around 3000m.
When they surface, they spend about two minutes before diving again, which means it is very difficult for researchers to observe and mark them.
In 2014, a whale was recorded diving for just over two hours, the longest period known underwater.
In the latest study, researchers recorded more than 3,600 dives from two dozen Cuvier’s beaked whales over a five-year period.
They recorded dives lasting about half an hour to two hours and thirteen minutes, well beyond when an animal of this size would have to lack oxygen.
But two dives by a single whale “astonished” the research team.
One lasted nearly three hours, another three hours 42 minutes.
“The longest dive for the species was around two and a half hours, so it’s the longest for Cuvier’s beaked whales, but it’s also the longest for all mammals,” said the Dr Nicola Quick, of Duke University in Durham, USA, to BBC News.
Although this individual was recorded completing these extremely long dives, Dr Quick says his study showed that a large percentage of the animals observed were able to sink for very long periods.
Researchers believe whales may have extremely slow metabolisms, possibly associated with larger-than-average oxygen stores, and an ability to tolerate build-up of lactic acid.
“The muscles in their body are sort of built differently than what you might expect from a deep diver,” said Dr. Quick.
“They have kind of a smaller brain and a fairly small lung volume. And they have a lot of good muscle tissue which is great for retaining oxygen stores, which probably helps them increase the duration of their dives.”
Fear may also have played a role in the record dive.
This species is vulnerable to killer whales and large sharks. Whales respond to threats by staying underwater as long as possible, until predators move away.
And deep diving may also have been in response to humans. The recording took place some 24 days after exposure to an active US Navy sonar signal, and researchers excluded them from their data set because they could have been potentially affected by the noise.
Cuvier’s beaked whales are known to be sensitive to sonar and other experts believe this may have impacted the length of the dive.
“The recorded dive time of over three hours is probably not typical, but rather the result of an individual being pushed to their absolute limits,” said Nicola Hodgkins of Whale and Dolphin Conservation, who was not involved in study.
“A single whale, considered already compromised due to its exposure to extremely high noise levels from military sonar, and therefore exhibiting abnormal behavior, has been recorded during such extreme dives.”
The research team found that there was little relationship between the length of the dive and the recovery time it takes for the whales to come back down.
Scientists believe that studying these deep-diving animals could offer clues to difficult questions such as cancer in humans.
“There is some interest in working with colleagues in oncology at Duke University, and even with Covid, as it involves the cells losing oxygen or being in hypoxic conditions,” said Dr Quick .
“So if these whales are in these hypoxic conditions in their tissues, and if we can find out what they were doing, could that have some other implication for human health or just for the health of the oceans in general?”
The study was published in the Journal of Experimental Biology.
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