Whales do not breathe water. Like all mammals, they possess lungs and must periodically surface to inhale atmospheric air. This biological requirement distinguishes them from fish, which extract oxygen directly from water using gills.
How Whales Breathe Air
Whales breathe using a specialized respiratory system. Instead of a nose, whales have nostrils, called blowholes, positioned on top of their heads. This placement allows them to take a breath with minimal effort, exposing only a small portion of their body to the surface.
When a whale surfaces, it forcefully exhales stale air, often creating a visible spout of mist. It then rapidly inhales fresh air. Strong muscles surrounding the blowhole seal it tightly, preventing water from entering their lungs as they dive. Unlike humans, who exchange about 10-15% of the air in their lungs with each breath, whales can efficiently replace 80-90%, optimizing oxygen intake for their underwater existence.
Unique Breathing Adaptations
Whales have remarkable adaptations for their deep-diving, air-breathing lifestyle. Unlike humans, whose breathing is an involuntary reflex, whales are conscious breathers. They must actively decide when to inhale and exhale, requiring them to keep at least one hemisphere of their brain awake even during rest. This voluntary control ensures they resurface for air and avoid drowning.
Their ability to hold their breath varies significantly by species. Many whales can remain submerged for an hour, but deep-diving species like the sperm whale can hold their breath for approximately 90 minutes. The Cuvier’s beaked whale holds the record among mammals, with documented dives lasting over two hours, sometimes up to 222 minutes.
Whales have high concentrations of myoglobin in their muscles, a protein that stores oxygen in the muscle tissue, supplementing the oxygen carried by hemoglobin in their blood. During dives, their heart rate significantly slows, a phenomenon called bradycardia, which can reduce their heartbeat to as low as 2-8 beats per minute in large whales. Blood flow is also selectively redirected to essential organs like the brain and heart, preserving oxygen for critical functions.
Mammals of the Ocean
Whales are classified as marine mammals. This classification highlights several key biological differences. Whales are warm-blooded, maintaining a consistent internal body temperature, and give birth to live young which they nurse with milk. In contrast, most fish are cold-blooded and typically lay eggs.
Fish use gills, specialized structures that extract dissolved oxygen from water. Gills are not designed to function in air, as their delicate structures collapse without water to support them. The oxygen concentration in air is also significantly higher than in water, explaining why whales must return to the surface.