The earliest cetaceans, known as pacicetans, lived about 50 million years ago. These four-legged creatures rarely exceeded a meter in length and bore a resemblance to wolves, though with a less noble build and a long snout. Fossils first identified in what is now Pakistan place these animals in the Eocene epoch, which spanned roughly 56 to 33.9 million years ago. At that time, the region was an isolated island off the coast of Eurasia. Many scientists propose that these early cetaceans led a semi-aquatic lifestyle and hunted fish, including prey similar to seals. Pacicetans had small hooves on their toes, and among living species, their closest non-cetacean relatives are the hippos.
Primitive marine mammals resembled furry crocodiles
Ambulocetes represent a transitional form between land-dwelling creatures and fully aquatic mammals. Their bodies were slender and streamlined, and they possessed elongated muzzles with eyes set higher on the skull. Ambulocetus likely hunted by ambushing prey near shorelines, much like crocodiles. It swam with a technique akin to otters, bending its front limbs and paddling with its hind legs while using its body and tail for propulsion. In this stage, cetaceans still retained some ability to move on land, though their gait would have been awkward. The fur of Ambulocetus remains a point of debate, with some depictions showing thick hair and others suggesting a nearly bald coat. The hindlimb bones preserve clues that later give rise to the flippers of modern marine mammals.
Dolphins communicate with individual names
Marine mammals convey information through sounds, and recent research has revealed striking sophistication in their vocal behavior. Each dolphin responds to a distinct whistle that appears to be an identity tag born with the animal and stable across its life. Analyses of dolphin vocalizations show patterns that function like names, with individuals tracking specific signals when they hear them underwater. This system likely helps pods stay together in low-visibility conditions, enabling coordinated movement and social bonding in a shared aquatic environment.
The songs of humpback whales spread widely
During mating seasons, whales produce elaborate melodic sequences that resemble songs. These themes are shared within a population but are not fixed; they evolve over time. Some songs gain popularity and spread across oceans. Recent observations show that a single song element can travel thousands of kilometers, from Polynesia to South America, through a chain of cultural transmission. Scientists continue to explore which topics and patterns become popular and how cultural exchange occurs among distant whale populations.
The sperm whale’secholocation organ once confused with a spermaceti bag
In the 18th and 19th centuries, spermaceti—a substance sourced from the heads of sperm whales—was highly valued in Europe. In its raw state, the material resembles a pouch, but as it is refined it separates into oily and waxy fractions. Spermaceti served purposes ranging from cosmetics and lighting to lubrication. In reality, the spermaceti organ is essential for the whale’s echolocation abilities, guiding orientation and space navigation during deep and murky dives.
Dolphins use tools to hunt
Although dolphins are well adapted for fishing, they sometimes rely on tools. In Australia’s Shark Bay, some dolphins insert flexible sea sponges over their snouts to shield their noses while foraging. This behavior appears to be learned, passed along within communities, and demonstrates a cultural dimension in marine mammals. In addition, dolphins employ clever techniques to retrieve hidden prey from shells: the animal places a shell on its beak, slides forward, lifts the shell, drains the liquid, and shakes free the catch. Such behaviors highlight problem-solving and social learning in dolphin cultures.