Dolphins, despite living entirely in aquatic environments, breathe air. As mammals, they share fundamental biological characteristics with land animals, including the need for atmospheric oxygen. Unlike fish, which use gills, dolphins possess lungs and must regularly surface to inhale air.
How Dolphins Breathe
Dolphins breathe through a specialized nostril on top of their heads called a blowhole. This complex structure is covered by a muscular flap that creates a watertight seal when submerged, preventing water from entering the lungs. When a dolphin surfaces, this flap opens, allowing for a rapid, forceful exhalation, often visible as a spout of air and water vapor. Following this, the dolphin quickly takes a deep, fresh breath before closing the blowhole tightly and diving back underwater.
Unlike humans, whose breathing is largely involuntary, a dolphin’s breathing is a conscious and voluntary act. This voluntary control is essential for their survival in an aquatic environment, as they must actively decide when to surface and breathe. Dolphins are remarkably efficient breathers, capable of exchanging up to 90% of the air in their lungs with each breath, significantly higher than the approximately 15% exchanged by humans.
Life Underwater and Air Breathing
Dolphins, as mammals, cannot breathe underwater like fish, requiring them to surface for air. This physiological need has led to specialized adaptations that enable them to thrive in their aquatic habitats. They exhibit a remarkable ability to hold their breath for extended periods, typically between 8 to 10 minutes, though some species can remain submerged for up to 15 minutes or more. This capacity is supported by efficient oxygen use, including a higher concentration of myoglobin in their muscles (which stores oxygen) and a higher volume of blood with more oxygen-carrying hemoglobin. When diving, dolphins employ a “dive reflex” that slows their heart rate (bradycardia) and redirects blood flow primarily to vital organs like the brain and heart, conserving oxygen for these sensitive tissues.
Even while resting or sleeping, dolphins maintain conscious control over their breathing through a unique phenomenon called unihemispheric sleep. During this state, one half of their brain remains active, allowing them to continue surfacing to breathe and stay aware of their surroundings, while the other half rests. This allows them to get the rest they need without losing consciousness and risking drowning.