The beluga whale is definitively not a porpoise, despite historically being called a “white porpoise.” Both belong to the biological order Cetacea (whales, dolphins, and porpoises), but they reside in different scientific families. Confusion stems from common names being used interchangeably for superficially similar marine mammals. Understanding the scientific classification and physical characteristics makes the distinction clear. The beluga is considered a medium-sized whale, setting it apart from smaller porpoises and dolphins.
Beluga Taxonomy and Classification
The beluga whale (Delphinapterus leucas) is classified within the suborder Odontocetes (toothed whales). This places it alongside dolphins and porpoises, distinguishing it from Mysticetes (baleen whales). The beluga belongs to the Family Monodontidae, a small group containing only two living species: the beluga whale and the narwhal.
Adult male belugas are medium-sized cetaceans, reaching up to 5.5 meters (18 feet) in length and weighing over 1,600 kilograms (3,530 pounds). Its genus name, Delphinapterus, translates to “dolphin without a fin.” The beluga is adapted to its Arctic and sub-Arctic environment, possessing a thick layer of blubber and entirely white coloration as an adult.
Defining the Difference: Porpoises vs. Dolphins
Dolphins and porpoises represent two distinct scientific families: Delphinidae and Phocoenidae. A reliable feature distinguishing the two groups is their teeth. Dolphins possess numerous conical teeth, while porpoises have teeth that are spade-shaped.
Dorsal fins provide an easy visual cue for identification. Dolphins typically have a prominent, curved, or hooked dorsal fin (falcate). Porpoises usually have a small, triangular dorsal fin that is less curved and more rigid.
Porpoises lack the pronounced snout or “beak” characteristic of many dolphin species, instead having a rounded or blunt head. Dolphins have a leaner, more streamlined body shape compared to the stockier build of porpoises. These differences reflect a long evolutionary divergence. The porpoise family includes only six species globally, compared to approximately 32 species of oceanic dolphins.
Key Distinctions: Belugas vs. Porpoises
The distinctions between beluga whales and porpoises are pronounced, starting with sheer size. The largest porpoise, the Dall’s porpoise, reaches a maximum of 2.4 meters and 220 kilograms. In contrast, the beluga is nearly twice as long and can weigh up to seven times more, classifying it as a whale.
A structural difference involves the dorsal feature. Porpoises possess a small, triangular dorsal fin, though some species, like the finless porpoise, may have only a low ridge. The beluga whale completely lacks a true dorsal fin, possessing only a tough, low dorsal ridge that helps it move easily under Arctic ice sheets.
Belugas possess a unique neck flexibility not shared with porpoises. Unlike most cetaceans, a beluga’s seven cervical vertebrae are not fused together. This allows the beluga to turn its head laterally and nod, whereas a porpoise has a stiffer neck and must move its entire body to change its field of view.
Although both are toothed whales, their dental structures differ significantly. Porpoises are characterized by their spade-shaped teeth, which are unique within the suborder Odontocetes. Beluga whales, like dolphins, possess simple, peg-like, conical teeth used to grasp prey before swallowing it whole.