Whales possess jaws, as they are mammals whose jaw structure is a modified version of the basic mammalian design. While all whales have the fundamental skeletal components of a jaw, their form and function have specialized dramatically based on diet and sensory needs. This adaptation has resulted in two distinct jaw types: the robust, toothed jaw of predators and the massive, flexible jaw of filter feeders.
The Mammalian Foundation: Basic Jaw Structure
The whale jaw, like that of all mammals, is composed of the paired lower jaw bones (mandibles) and the upper jaw (maxilla). The most significant departure from terrestrial mammals is the structure of the mandibular symphysis, the joint where the two halves of the lower jaw meet. In modern baleen whales (Mysticetes), this connection is not a rigid fusion but a highly elastic, ligamentous articulation.
This loose connection provides flexibility, allowing the mandibles to rotate and bow outward. The bones are also adapted for an aquatic existence, featuring a lighter, more porous structure compared to land mammals. This lighter bone assists with buoyancy and facilitates the transmission of sound through the skull, which is necessary for navigating and communicating underwater.
Predatory Adaptation: Jaws of Toothed Whales
Toothed whales (Odontocetes), including dolphins, orcas, and sperm whales, possess jaws adapted for active, high-speed hunting. Their robust mandibles are equipped with numerous teeth, which are generally uniform in shape and used primarily for gripping and securing prey, rather than chewing. Powerful musculature allows for a strong, decisive bite necessary to hold onto fish and squid.
The lower jaw in Odontocetes also performs a sensory function by receiving sound for echolocation. The mandible contains a thin, hollow area of bone at the back, known as the panbone, which is filled with a specialized fat pad. This fat-filled cavity acts as an “acoustic window,” efficiently channeling returning echolocation clicks from the water to the inner ear.
Specialized Feeding: Jaws of Baleen Whales
Baleen whales (Mysticetes), such as the blue and humpback whales, have jaws evolved for bulk filter feeding. Their jaws are characterized by colossal size and remarkable flexibility, necessary for lunge feeding. The lower jaw consists of two massive, bow-shaped mandibles loosely connected at the symphysis by a highly elastic fibrocartilage joint.
This elastic joint, combined with highly extensible throat pleats, allows the mouth cavity to expand dramatically. When a whale lunges into prey, its jaw rotates outward, engulfing a volume of water and small organisms. The upper jaw is toothless, instead supporting hundreds of plates of keratinous baleen, which act as a massive sieve to strain krill and small fish. A sensory organ lodged between the tips of the mandibles coordinates the complex mechanics of the lunge.