Dolphins are a type of whale, a common point of confusion due to their distinct names. Both are marine mammals belonging to the order Cetacea. These animals share common characteristics such as being warm-blooded, breathing air, and nursing their young in the ocean.
Understanding the Cetacean Family Tree
The scientific classification of marine mammals clarifies the relationship between dolphins and whales. All whales, dolphins, and porpoises are grouped under the order Cetacea. This order is further divided into two main suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales). This taxonomic structure means that all dolphins are categorized within the larger “whale” group.
Baleen whales, such as blue whales, humpback whales, and fin whales, have baleen plates instead of teeth. These plates are made of keratin and filter small prey like krill and plankton from the water. In contrast, toothed whales possess teeth and actively hunt their prey, which can include fish, squid, and other marine mammals.
Dolphins are part of the Odontoceti suborder, making them a type of toothed whale. This diverse suborder encompasses about 75 species, including dolphins, sperm whales, beluga whales, and beaked whales. While all dolphins are whales, not all whales are dolphins, as the group also includes baleen whales and other toothed whales.
Distinctive Traits of Dolphins
Within the diverse group of toothed whales, dolphins exhibit distinguishing characteristics. They are generally smaller than many other toothed whales; for example, a sperm whale can reach 20 meters, while common dolphins are typically around 2.5 meters. Their streamlined bodies often feature a pronounced beak, contributing to agile movement.
Dolphins possess conical teeth, adapted for grasping prey like fish and squid. This differs from other odontocetes with varied tooth shapes, such as porpoises’ spade-shaped teeth or a narwhal’s single tusk. Beyond physical traits, dolphins are highly social, often living in groups called pods that can include hundreds or thousands of individuals. They communicate through vocalizations, including clicks and whistles, and exhibit cooperative hunting behaviors.
Dolphins use echolocation, a biological sonar system they use to navigate and hunt. They emit high-frequency sound pulses, which travel through an organ in their head called the melon, then bounce off objects and return as echoes. These echoes are received by the dolphin’s lower jaw and forehead, allowing them to interpret the location, size, shape, and even internal structure of objects, providing a detailed “sound picture” of their surroundings. Many toothed whales use echolocation, but dolphins’ use of this sense is well-documented.