The common perception of cetaceans often contrasts immense whales with small, sleek dolphins. This view is challenged by the two species of pilot whales—the long-finned and the short-finned. These marine mammals possess the size and heft that seem to justify the “whale” in their name, yet they exhibit biological traits associated with their smaller cousins. Their classification as dolphins resolves the confusion of their common name.
The Taxonomic Answer: Why Pilot Whales Are Dolphins
Pilot whales are unequivocally classified as dolphins, despite their misleading common name. This determination is based on the scientific family to which they belong: Delphinidae, the family of oceanic dolphins. The genus Globicephala, which includes both the long-finned and short-finned pilot whales, shares a direct lineage with smaller dolphins, as well as the largest dolphin, the orca.
All members of the family Delphinidae are part of the Odontocetes suborder, meaning they are toothed whales, in contrast to the filter-feeding baleen whales. Pilot whales exhibit the defining characteristics of oceanic dolphins, possessing conical teeth designed for catching prey, primarily squid, which forms the bulk of their diet. They also navigate and hunt using a sophisticated form of sonar called echolocation. The name “pilot whale” is a historical artifact, likely given by whalers who noted their large size compared to other local dolphins.
Physical Differences That Make Them Look Like Whales
The reason pilot whales carry the “whale” label is due to their imposing physical presence, which sets them apart from the more familiar, slender dolphins. They are the second-largest species in the dolphin family, exceeded only by the orca, with males reaching lengths up to 6.7 meters (22 feet) and weights exceeding 3,000 kilograms. This sheer bulk gives them a robust, non-streamlined appearance.
A distinguishing feature is the pilot whale’s massive, bulbous forehead, known as the melon. This rounded organ, composed of fatty tissue, protrudes significantly past the mouth, giving the animal a blunt, almost-beakless profile. Furthermore, their dorsal fin is thick and low-set with a broad base, often described as curved or falcate, which differs from the tall, triangular fins seen on many smaller dolphin species.
Complex Social Structure and Intelligence
Pilot whales are defined by their highly developed social structures, a trait common among the dolphin family. They live in remarkably cohesive, stable pods that are often organized around female lineages, a structure known as a matriarchy. Individuals typically remain with their birth pod for their entire lives, fostering deep, intergenerational bonds.
This intense social cohesion allows for complex behaviors, including cooperative hunting, where the pod works together to corral schools of squid. The short-finned pilot whale is also one of the few non-human mammals, along with the orca, where females undergo menopause. This allows post-reproductive females to dedicate decades to guiding and supporting their family unit. The species is notorious for mass strandings, a puzzling phenomenon historically linked to their powerful social loyalty, where a sick or disoriented individual is followed ashore by the entire pod. However, recent genetic studies suggest that mass strandings may involve the mixing of multiple, unrelated groups, potentially indicating navigation errors rather than just unbreakable kinship.