Whales, as air-breathing mammals, cannot breathe through their mouths. Whales have evolved a highly specialized anatomy that completely separates their respiratory and digestive systems. The mouth is primarily dedicated to feeding, while the process of gas exchange is handled by a single, specialized opening. This anatomical adaptation is necessary for life in the ocean, as it eliminates the risk of water entering the lungs during feeding or diving.
The Mechanics of Blowhole Respiration
Whales breathe exclusively through a structure known as the blowhole, which is the external, modified nostril located on the top of the head. This dorsal location allows the whale to take a breath by exposing only a small portion of its body at the water’s surface. Baleen whales possess two blowholes, while toothed whales have a single one.
Breathing for a whale is a voluntary, conscious action, meaning they must actively decide when to take a breath, unlike the automatic, involuntary respiration in humans. When the whale surfaces, it forcefully exhales, creating the visible spout of water vapor and mucus known as the “blow.” This explosive exhalation and subsequent inhalation cycle is remarkably fast, often lasting only one to two seconds in large rorquals.
This rapid air exchange is also highly efficient, with a whale renewing up to 90% of the air in its lungs with each breath. By comparison, a human typically exchanges only 10 to 15% of the air capacity during a normal breath. Strong muscles surrounding the blowhole maintain a tight, watertight seal when the whale is submerged, preventing water from entering the respiratory tract.
The Internal Anatomy That Prevents Oral Breathing
The absolute separation of the whale’s airway and digestive tract is the primary biological reason oral breathing is impossible. The respiratory passage, or trachea, leads directly from the blowhole to the lungs, independent of the mouth and pharynx area. This arrangement ensures that the path for air and the path for food never intersect, a crucial adaptation for a creature that feeds underwater.
The laryngeal structure, sometimes called the larynx, is highly adapted to plug into the nasal passage, creating a physical barrier. This tight fit ensures that any water that enters the mouth can only pass down the esophagus to the stomach, bypassing the lungs entirely. The specialized musculature of the pharynx only permits the passage of either air or food, never both simultaneously.
The Oral Plug
In lunge-feeding whales, such as humpbacks and fin whales, a muscular structure called the “oral plug” further reinforces this separation. This bulbous part of the soft palate blocks the channel between the mouth and the pharynx during lunge feeding, a process where the whale engulfs enormous volumes of water and prey.
When the whale swallows, the oral plug shifts backward and upward, allowing food to pass while simultaneously protecting the upper airway from food or water entry. The lower respiratory tract is also protected by laryngeal cartilages and a muscular sac that forces upward to completely seal the airway when swallowing occurs. This intricate, dynamic valve system dedicates the pharynx entirely to digestion, eliminating the risk of choking and drowning.
The Mouth’s Dedicated Function: Feeding
The mouth’s dedicated function is the ingestion and processing of food. Its size and structure are specifically evolved for feeding methods that do not involve gas exchange.
Baleen whales utilize their mouths for filter feeding, where they take in tons of water and small prey, like krill, before filtering the water out through their baleen plates. Toothed whales, like dolphins and sperm whales, use their mouths and teeth for predation, capturing and swallowing fish or squid whole.