Let’s learn about whales and dolphins

These cetaceans are mammals that live in the water

a humpback whale and her baby swimming just under the water's surface

A huge humpback whale and her baby swim near the sea surface. These are among the whales that filter their food from the water using baleen plates.

UWPhotog/iStock/Getty Images Plus

Whales, dolphins and porpoises all live in water, but they’re not fish. They’re water-dwelling mammals known as cetaceans (Seh-TAY-shuns). This group includes the largest animals on Earthblue whales — which can grow up to 29.9 meters (98 feet) in length. Most cetaceans live in the ocean, but there are a few species that live in freshwater or brackish water (water that is salty, but not as salty as the ocean). Cetaceans don’t have gills as fish do. To get the oxygen they need, these mammals breathe in air through structures called blowholes.

Cetaceans are split into two groups based on what and how they eat. Toothed whales — such as sperm whales, orcas (killer whales), dolphins, narwhals and porpoises — all have teeth that help them catch prey. They eat fish, squid and other large critters. Orcas have been known to eat penguins, seals, sharks and other whales. Most species of toothed whales can use echolocation to find prey.

Baleen whales lack teeth. Instead, plates of baleen line their mouths. That baleen is made of keratin — the same stuff as hair — and lets the whale filter krill and other small invertebrates from the water to eat. Humpback whales in Alaska, though, have figured out they can get a free meal of tiny salmon by hanging out at fish hatcheries.

Scientists have had to get creative when it comes to studying these animals. One group figured out how to weigh a whale using drone imagery. Others use acoustic tags and other techniques to study the social lives of whales and dolphins. And sometimes scientists just get lucky. Like when researchers driving an underwater robot came across a decomposing whale at the bottom of the ocean — and found an entire community feasting on the dead.

Want to know more? We’ve got some stories to get you started:

Why some whales become giants and others are only big Being big helps whales access more food. But just how big a whale can get is influenced by whether it hunts or filter-feeds. (1/21/2020) Readability: 6.9

The social lives of whales New tools are giving scientists an unprecedented glimpse into the behaviors of whales and dolphins. And these new data are upending long-held assumptions. (3/13/2015) Readability: 7.0

Whales get a second life as deep-sea buffets When a whale dies and sinks to the seafloor, it becomes a feast for hundreds of different types of creatures. (10/15/2020) Readability: 6.6

The beautiful, haunting songs performed by some species of whales let the animals communicate over long ocean distances.

Explore more

Scientists Say: Krill

Scientists Say: Echolocation

Explainer: What is a whale?

Cool Jobs: A whale of a time

A whale of a journey

Drones help scientists weigh whales at sea

Whales feast when hatcheries release salmon

Killer whale blows raspberry, says ‘hello’

Sperm whales’ clicks suggest the animals have culture

Whales echolocate with big clicks and tiny amounts of air

Whale blowholes don’t keep out seawater


Word Find

Learn more about whales and dolphins through crossword puzzles, coloring sheets and other activities from Whale and Dolphin Conservation. All of the activities are presented in English — and Spanish. French and German translations also are available.

Sarah Zielinski is the Editor, Print at Science News Explores. She has degrees in biology and journalism and likes to write about ecology, plants and animals. She has three cats: Oscar, Saffir and Alani.

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