A team of researchers at the University of St Andrews in the UK developed a non-invasive wearable device that allows them to monitor what happens inside diving animals in unprecedented detail. Their device uses near-infrared spectroscopy to monitor blood volume and oxygenation of the animals.
“It’s effectively like a Fitbit,” says lead researcher Chris McKnight. “It does not penetrate the skin.”
McKnight and his team decided to study harbor seals. They found that seals have conscious control of their dive reflex, pre-tuning their bodies both before dives and subsequent surfacing.
Nearly every mammal, including us, has a dive reflex. This reflex triggers various changes in the body that aids in swimming underwater, including the reduction of blood flow to the skin and a reduction in heart rate which lowers the rate of oxygen consumption.
Scientists previously believed this dive reflex was an automatic response, one which is triggered in humans, for example, by the holding of the breath and the sensation of cold water hitting the face.
Recently, however, studies have begun to show that some diving mammals have degrees of control over this process.
When the team attached their device to the harbor seals, they found that the peripheral blood vessels of seals started to contract well before they dived – typically around 15 seconds before and sometimes as much as 45 seconds, reports New Scientist.
McKnight believes seals must do it under control. “There’s no other stimulus,” he says.
The seals also restored normal blood flow to the blubber several seconds before surfacing, again showing conscious control.
The team also discovered that when seals are feeding, they don’t bother to stay at the surface long enough to restore normal blood oxygen levels.
Researchers are now planning to study other mammals, including humans.