Dolphins are cetaceans, members of the same family as whales. All of these animals are mammals, which means that they share certain characteristics: They give birth to live babies, they feed their young milk, they are warm-blooded and they need to breathe air. Although dolphins are marine mammals and so spend much of their lives under water, they still must surface periodically to breathe.
How Dolphins Breathe
Dolphins aren’t equipped to breathe through their mouths because they spend their lives in the water and could drown while feeding. They also lack a nose that looks like what people or other land animals have. Instead, dolphins breathe through nostrils located on top of their heads, called blowholes. When the dolphin surfaces, he can blow the old air out of his lungs, creating a plume of spray and suck in fresh air. His blowhole seals immediately after he breathes so that he won’t get water in his lungs.
How Often Dolphins Breathe
The frequency with which dolphins need to breathe varies somewhat and depends on how active the dolphin is at any given time. According to Bruce Hucker of the South Carolina Aquarium, dolphins average about eight to 12 breaths per minute when they’re moderately active but breathe as few as three times per minute when they’re resting. Groups of dolphins sometimes stay under water longer and may dive together for six minutes or more. When they surface, they take a very quick breath and are immediately ready to dive under water again. During very deep dives, it’s possible for dolphins to stay under water as long as 15 minutes before needing a breath.
How Dolphins Breathe While Sleeping
Scientists think that the cetacean breathing mechanism is voluntary, which means that dolphins only breathe when their blowholes are out of the water and it’s safe to do so. If they enter deep sleep, they might not be able to tell when to breathe, so they’ve developed a couple of ways to handle sleeping. When a dolphin sleeps, only half his brain goes to sleep at any one time; the other half of the brain stays awake and takes care of making sure that he keeps breathing. A dolphin also may sleep at the surface of the water with his blowhole exposed.
How Dolphins Can Suffocate
It is rare for dolphins to drown by inhaling water but they can suffocate from lack of air. Newborn dolphins who are born when too deep under water to reach the surface can die of suffocation quickly before ever taking their first breath. Dolphins of any age can become tangled in underwater hazards such as fishing nets and suffocate when they can’t surface for air. Sick dolphins may not be strong enough to swim up for air; healthy dolphins have been seen holding sick dolphins at the surface to allow them to breathe to prevent suffocation.
- Defenders of Wildlife: Basic Facts About Dolphins
- Scientific American: How Do Whales and Dolphins Sleep Without Drowning?
- University of Michigan Animal Diversity Web: Bottlenosed Dolphin
- University of Michigan Animal Diversity Web: Short-Beaked Saddleback Dolphin
- University of Michigan Animal Diversity Web: Southern Right Whale Dolphin
- University of Michigan Animal Diversity Web: Rough-Toothed Dolphin