Scientists at the University of British Columbia believe they’ve solved a whale mystery.
Researchers have spent decades trying to understand why whales don’t get brain damage when they dive — also called fluking — or move.
Land mammals such as horses experience pulses in their blood when galloping — their blood pressure goes up and down on every stride, said Margo Lillie, lead author of the study published in a recent edition of the journal Science.
While the same phenomenon occurs in marine mammals that swim with dorso-ventral movements, whales are able to avoid long-term damage.
“Long-term damage of this kind can lead to dementia in human beings,” said Lillie. “But while horses deal with the pulses by breathing in and out, whales hold their breath when diving and swimming. So if cetaceans can’t use their respiratory system to moderate pressure pulses, they must have found another way to deal with the problem.”
The team’s research suggests whales have special blood vessels in their brain to protect them from blood pulses that could otherwise damage the brain when they swim.
The researchers believe whales use a “pulse transfer” mechanism to ensure there is no difference in blood pressure during movement, which is why they don’t end up with brain damage.
“The arteries will actually pass through the veins so you can really see how pressure in one will be transmitted to the other and equalized,” said researcher Wayne Vogl.
Colleague Bob Shadwick says it’s always been “sort of a perplexing problem” when it comes to how whales dive. “So it links it very nicely to whales that actually swim sort of like this, rather than lateral movements like seals do,” says Shadwick. “Seals do not have this because they don’t experience the same sort of internal body-cavity pressure changes when they swim.”
Shadwick says the model could be used to ask questions about what’s happening with other animals’ blood pressure pulses when they move.
The research was done through computer modelling and still needs to be tested directly by measuring blood pressure and flow in the brains of the swimming cetaceans, which is currently not considered ethical or technically possible.
Understanding how the thorax responds to water pressure at depth and how the lungs influence vascular pressure is an important next research point, according to Vogl.
“They are the biggest animals on the planet, possibly ever, and understanding how they manage to surge and live and observe what they do is a fascinating piece of basic biology,” said Lillie.