Whales and dolphins are both members of the order Cetacea, a group of marine mammals that share a common evolutionary history. This relationship often creates public confusion about where the line is drawn between the two groups. Although the vast majority of the nearly 90 species of whales pose no threat to dolphins, the marine food web has one significant exception. This article provides a clear, science-based answer regarding the predatory relationship between certain whales and dolphins.
The Definitive Answer: Killer Whales
Yes, whales do eat dolphins, but the answer applies almost exclusively to a single species: the Killer Whale, or Orca. Despite its common name, the Orca is the largest member of the oceanic dolphin family, Delphinidae, making it a dolphin that preys on other dolphins. The Orca sits at the top of the marine food chain as the ocean’s apex predator.
Orcas possess the necessary combination of intelligence, size, and speed to successfully hunt other marine mammals, including various species of dolphins and porpoises. Not all Orcas participate in this predation, as different populations, known as ecotypes, have specialized diets. The group responsible for hunting marine mammals, including dolphins, are known as Transient or Bigg’s Killer Whales.
These Transient Orcas follow a diet that focuses on warm-blooded animals, which includes seals, sea lions, and other small cetaceans like the Pacific white-sided dolphin, common dolphin, and Dall’s porpoise. This specialization separates them from other populations, like Resident Orcas, whose diet consists almost entirely of fish, primarily Chinook salmon. The existence of these distinct ecotypes means that a dolphin’s safety can depend entirely on which type of Killer Whale pod it encounters.
Analyzing Predatory Behavior and Tactics
The successful hunting of swift and intelligent prey like dolphins requires coordinated, social strategies from the Transient Orca pods. Orcas are often referred to as the “wolves of the sea” because they hunt in highly organized groups. The pod will work together to pursue and exhaust their prey, often engaging in prolonged chases.
A common tactic is to use multiple individuals to herd the dolphins, separating a single animal from its group, as a lone dolphin is easier to dispatch. Once isolated, the Orcas may use high-impact maneuvers, such as ramming the dolphin with their bodies or using powerful tail slaps to stun it. This method of stunning prey reduces the risk of injury to the Orcas during the final attack.
Dolphins are a component of the broader marine mammal diet of the Transient ecotype, which also includes larger prey like Minke whales and Gray whale calves. The ability of these Orcas to take down large prey is directly related to their sheer size, with adult males reaching up to 32 feet in length and weighing over six tons. Observations of these hunts also reveal a complex social structure, as the Orcas often share the spoils of the hunt among family members, sometimes allowing calves to eat first.
Why Most Other Whales Are Not Hunters
Most whale species are not predators of dolphins due to fundamental differences in their feeding anatomy and dietary specialization. The order Cetacea is divided into two suborders: Odontocetes (toothed whales) and Mysticetes (baleen whales). The Killer Whale is the primary example of a toothed whale that hunts dolphins, but the other 70 or so species of whales do not share this habit.
Baleen whales, which include the largest animals on Earth like Blue, Humpback, and Gray whales, are filter feeders. Instead of teeth, their mouths contain large, fringed plates of keratin called baleen, which act like a sieve. These whales feed by taking in massive gulps of seawater and then pushing the water out, trapping tiny organisms like krill, plankton, and small schooling fish in the baleen. Their feeding mechanism is designed to consume small prey in huge volumes, making it physically impossible for them to hunt and consume a dolphin.
Other large toothed whales, such as the Sperm Whale, have highly specialized diets. Sperm Whales are deep-sea divers, known for hunting giant and colossal squid in the ocean’s dark depths, routinely diving to 2,000 feet or more. Their diet is primarily composed of squid, deep-sea fish, and sometimes sharks, a niche that does not overlap with surface-dwelling dolphins. While they are powerful predators, their hunting focus is the deep-sea cephalopods, not the agile, fast-moving dolphins of the upper ocean layers.