Environment

Fact-checked

Do All Mammals Have a Diving Reflex?

Last Modified Date: February 13, 2024

The diving reflex refers to the body’s physiological response to being submerged in water. It includes the selective shutting down of body parts to conserve the energy needed to survive. Though most prevalent in aquatic mammals like seals, otters, whales, and dolphins, it exists in other mammals, too. In fact, all mammals, including humans, have a diving reflex that automatically prioritizes the delivery of oxygen to the brain and heart when underwater.

When a mammal immerses its face in cold water, the trigeminal nerve sends signals to the brain, activating the vagus nerve, part of the autonomic nervous system. It is the autonomic nervous system that controls heart rate and breathing without us having to think about it. When activated, the vagus nerve will slow the mammal’s heart rate, enabling the heart to function despite the lack of oxygen.

Though most notable in aquatic mmammals, all mammals – including humans – have a diving reflex that automatically prioritizes the delivery of oxygen to the brain and heart when underwater.

The diving reflex is generally a mild response in humans, but aquatic mammals rely on it to function. After all, they need to be able to withstand the pressures associated with diving – sometimes at great depths – for food. They have to be able to hunt and chase their prey without needing to take a breath.

A deep dive into the diving reflex:

Compared to adults, children are able to survive longer when deprived of oxygen underwater. Their bodies cool more quickly, so they exhibit a more intense diving reflex and can absorb more oxygen into their bloodstream. The more intense the dive reflex is, the better preserved the tissues are. This helps provide a better chance of recovering in near-drowning situations.

As a result, when children go underwater, there is more oxygen available to them than to adults. For example, thanks to the diving reflex, a 21-month-old was able to survive after falling into a freezing river in Colorado. Despite the fact that his heart had stopped and he was no longer breathing, he was revived an hour later and recovered completely only a few days later.

Weddell seals have been known to dive to depths of 2,300 feet for up to 80 minutes without needing to surface for air, all thanks to the diving reflex.

Also thanks to the diving reflex, elephant seals can dive more than 5,000 feet while holding their breath. This reflex also allows them to spend more than 80 percent of their time underwater during migration.

AS FEATURED ON:

Discuss this Article