Whales, dolphins, and porpoises are mammals that must surface to breathe, accomplishing this through a specialized respiratory opening called the blowhole. This feature is essentially the whale’s nostril, which has migrated to the top of the head over the course of evolution. This dorsal positioning allows the animal to take a full breath with minimal effort, exposing only a small part of its body at the water’s surface. The blowhole functions as the sole gateway for air exchange between the lungs and the atmosphere.
The Blowhole’s Anatomy and Breathing Mechanism
The blowhole is a direct connection to the respiratory system, leading straight to the lungs through the trachea. Unlike terrestrial mammals, a whale’s respiratory tract is completely separate from its digestive tract, meaning the animal cannot breathe through its mouth. This anatomical separation ensures that water cannot enter the lungs, making it impossible for a whale to choke while feeding underwater.
When a whale is submerged, the blowhole is sealed by powerful, muscular flaps and fibrous plugs that remain closed in a relaxed state. To breathe, the whale must consciously contract these muscles to open the blowhole as it breaks the surface, highlighting that breathing is a voluntary, deliberate action. The exhalation is an explosive event, forcefully expelling stale air from the lungs before a rapid, deep inhalation of fresh air follows.
This process is extraordinarily efficient; large rorqual whales can complete their entire inhale-exhale cycle in just one or two seconds. Whales renew about 80 to 90 percent of the air in their lungs with each breath. By contrast, a human typically replaces only 10 to 15 percent of their lung air during a normal breath, demonstrating the adaptation for maximizing oxygen uptake before a dive. The blowhole’s location and robust sealing mechanism are fundamental to the whale’s ability to undertake deep, prolonged dives.
Structural Differences: One Blowhole or Two
The number of blowholes a whale possesses serves as a clear physical indicator of its suborder, dividing all cetaceans into two major groups. Toothed whales (Odontocetes) have a single blowhole located toward the top of their head. This group includes species such as dolphins, porpoises, and the sperm whale. The single opening results from one of the ancestral nasal passages evolving to serve a different function.
The other ancestral nasal passage in toothed whales became integrated into the complex sound production system used for echolocation. This biological sonar is essential for navigation and hunting in the deep ocean environment. In contrast, all baleen whales (Mysticetes) possess two distinct blowholes situated side-by-side.
These paired blowholes are homologous to the two nostrils found in most other mammals. Species in this suborder, like the humpback, blue, and gray whales, use baleen plates instead of teeth to filter small prey from the water. The dual openings often create a characteristic V-shaped mist when the whale exhales, which researchers use for identification. Evolutionary studies suggest the repositioning of the nasal passages occurred differently in these two suborders, with toothed whales showing distinct skull changes compared to the baleen whales.
The Whale Spout: Condensation, Not Water
The dramatic plume visible when a whale surfaces, often called the “spout” or “blow,” is a common source of misunderstanding. The cloud is not a jet of water expelled from the whale’s lungs; expelling water would cause the animal to drown. Instead, the visible plume is primarily the whale’s warm, moist breath, saturated with water vapor from the lungs.
When this warm, pressurized air is forcefully released into the cooler atmosphere, the water vapor quickly condenses. This rapid condensation creates the distinctive, misty cloud, similar to how a person’s breath becomes visible on a cold day. The spout also contains a small amount of mucus and oil droplets from the respiratory tract, along with any seawater resting over the blowhole when it opened.
The height, shape, and angle of the spout are unique to different species, allowing observers to identify the whale from a distance. For example, the North Atlantic right whale produces a characteristic V-shaped spout, while blue whales generate a tall, straight column. This visible exhalation is a necessary action, helping the whale rapidly clear its lungs of carbon dioxide-rich air before taking a fresh, deep breath.