Dolphins are indeed a type of whale, though the term often confuses those outside of marine biology. These intelligent marine mammals belong to the scientific order Cetacea, which encompasses all whales, dolphins, and porpoises. More specifically, dolphins are classified under the suborder Odontoceti, meaning they are part of the group known as toothed whales. This classification places them alongside much larger animals, such as the sperm whale and the orca, which is itself the largest species of dolphin.
The Odontocete Suborder
The Odontoceti suborder is defined by physical and sensory traits that distinguish its members from other cetaceans. A singular, defining characteristic is the presence of teeth, which are typically uniform and conical, used primarily for grasping prey rather than chewing it. These animals possess only one blowhole, located on the top of their head. This single opening is an adaptation linked to the way they produce sound.
Toothed whales are unified by their advanced sensory system known as echolocation. They produce high-frequency clicks that are focused and projected forward through an organ in the forehead called the melon. The returning echoes are received through the lower jaw and transmitted to the inner ear, allowing the animal to create a detailed map of its environment and locate prey, even in complete darkness. This diverse group includes approximately 73 species, encompassing the small harbor porpoise, the immense sperm whale, and the highly social beluga whale.
Defining Dolphins (Family Delphinidae)
Dolphins represent the largest family within the Odontoceti suborder (Delphinidae), and are often referred to as oceanic dolphins. Species in this family are typically characterized by a streamlined body built for speed and agility, often featuring a prominent, elongated snout, or beak. Their teeth are generally conical or peg-like, with some species having over 100 teeth in their jaws, which aids in catching slippery prey like fish and squid.
Delphinidae is recognized for its complex social structures, with most species living in cooperative groups called pods. These dolphins display an exceptional level of intelligence and complex learned behaviors, which are facilitated by their large, highly developed brains. The size range within this family is significant, extending from the relatively small Hector’s dolphin to the Orca, a species that can grow up to 10 meters long and is sometimes called the killer whale.
Toothed Whales Versus Baleen Whales
The two main suborders of cetaceans, Odontoceti (toothed whales) and Mysticeti (baleen whales), are distinguished by their fundamental feeding strategies and physical structures. Unlike the toothed whales’ active hunting and grasping of individual prey, baleen whales are filter feeders. Mysticetes possess rows of keratin plates, known as baleen, hanging from their upper jaw, which they use to sieve vast quantities of small organisms like krill and plankton from the water.
Baleen whales possess two separate blowholes, while toothed whales have only one. Furthermore, Mysticetes typically lack the sophisticated echolocation system present in Odontocetes, instead relying on low-frequency sounds for long-distance communication and navigation. While many baleen whales are the largest animals on Earth, with the blue whale being the largest, toothed whales have diversified into a much greater number of species, with over 70 distinct types.
Dolphins Versus Porpoises
The distinction between dolphins and porpoises is a frequent source of confusion, though both are small Odontocetes. Porpoises belong to the family Phocoenidae, which is separate from the dolphin family, Delphinidae, and they exhibit several clear physical differences. The shape of the teeth is one of the most reliable identifiers, as dolphins have pointed, cone-shaped teeth, whereas porpoises have flattened, spade-shaped teeth.
Porpoises generally have a more compact and stocky body shape compared to the leaner, more streamlined bodies of most dolphins. Their dorsal fins also differ markedly; most dolphins have a curved or hooked dorsal fin, while porpoises typically have a smaller, more triangular-shaped dorsal fin. Finally, dolphins usually possess a pronounced beak or rostrum, giving them a longer snout, while porpoises tend to have a shorter, more rounded head with no distinct beak.