Pilot whales are frequently encountered in global temperate and tropical waters, leading many people to wonder about their proper classification. Although the common name suggests a connection to larger cetaceans, their physical characteristics and behaviors are often more aligned with dolphins. This confusion stems from a difference between formal scientific grouping and the common names given by early observers. Understanding where the pilot whale fits in the tree of life resolves this ambiguity.
The Scientific Classification
The definitive answer to whether a pilot whale is a dolphin lies in its taxonomy. Pilot whales belong to the family Delphinidae, which encompasses all oceanic dolphins. This grouping places them firmly with animals like the common dolphin and the bottlenose dolphin, not with baleen whales.
All cetaceans fall under the order Cetacea. Pilot whales are classified as Odontocetes, or toothed whales, differentiating them from filter-feeding baleen whales. Delphinidae is a sub-group within the toothed whales, and pilot whales are among the largest members, second only to the orca.
There are two recognized species: the long-finned pilot whale (Globicephala melas) and the short-finned pilot whale (Globicephala macrorhynchus). They are distinguished by the length of their pectoral fins and skull morphology. The long-finned species prefers cooler, temperate waters, while the short-finned species is found in tropical and sub-tropical regions.
Why They Are Called Whales
The common usage of “whale” reflects historical observation and relative size rather than scientific grouping. Pilot whales are substantial animals, with males reaching lengths up to 6.7 meters and weighing several tons. This sheer size made them comparable to smaller toothed whales in the eyes of early observers.
When contrasted with typical small dolphins, the pilot whale’s robust body and large frame naturally led to the association with the word “whale.” They are also often included with other large, dark-colored dolphins under the general term “blackfish.”
The “pilot” part of the name originated from an early, incorrect theory that each pod was guided by a single leader. This historical naming convention has persisted in common language, despite taxonomy categorizing them as dolphins.
Physical and Behavioral Traits
The most recognizable physical feature is the large, bulbous forehead, known as the melon, which gives the head a round, almost square profile. This melon is filled with fatty tissue and functions to focus the sounds used for echolocation. Echolocation is necessary for navigating and hunting in the deep ocean.
Unlike many dolphins, pilot whales have a very short or absent snout. Their dorsal fin is broad, low, and shaped like a backward-sweeping sickle. They generally have a dark coloration, often with a light-colored, anchor-shaped patch on the chest. Males exhibit sexual dimorphism, having a larger, more pronounced melon and a bigger dorsal fin than females.
Pilot whales are highly social animals that live in stable, matriarchal family groups, or pods. Pods typically contain 10 to 30 individuals, but they can congregate into larger super-pods of hundreds of animals. Their strong social cohesion is believed to be a factor in their tendency toward mass strandings, where the entire group follows a single distressed member into shallow water.
Their diet primarily consists of squid, which they pursue by undertaking deep, prolonged dives. They are capable of diving to depths exceeding 600 meters to hunt their prey, often performing these foraging dives at night.