Whales eat everything from tiny shrimp-like krill to giant squid to other whales, depending on the species. The nearly 90 known whale species fall into two groups: baleen whales, which filter enormous quantities of small prey from the water, and toothed whales, which hunt individual fish, squid, and sometimes marine mammals. What unites them is scale. A blue whale can consume more than 16 tonnes of krill in a single day, while a sperm whale dives thousands of feet to hunt squid the size of a school bus.
Baleen Whales: Built for Filter Feeding
Baleen whales don’t have teeth. Instead, their mouths contain rows of baleen plates, flexible structures made of keratin (the same material as your fingernails) that hang from the upper jaw like a curtain. These plates act as a massive strainer. The whale takes in a huge mouthful of water, then pushes it out through the baleen with its tongue, trapping thousands of tiny prey inside.
Blue whales, the largest animals ever to live, feed almost exclusively on krill, small crustaceans that grow to about six centimeters long. Right whales, minke whales, fin whales, and sei whales also eat primarily krill, though they sometimes take in copepods (even tinier crustaceans) and small fish. Humpback whales and Bryde’s whales actively hunt small schooling fish like herring and anchovies in addition to krill.
Gray whales are the outliers. Rather than filtering prey from open water, they feed along the ocean floor, sucking up sediment and straining out bottom-dwelling creatures. In the Arctic, they target benthic amphipods, tiny shrimp-like animals that live in the mud. Researchers using video tags have also documented gray whales feeding on ghost shrimp in shallow intertidal zones during high tide, rolling on their sides to vacuum up prey from the seafloor.
How Much a Blue Whale Eats Per Day
A blue whale can weigh up to 180 tonnes, and fueling that body takes staggering amounts of food. Research from Stanford University’s Hopkins Marine Station found that a blue whale in the eastern North Pacific ingests an average of 16 tonnes of krill per day during feeding season. That’s roughly 12% of its own body weight, every single day.
The catch is that this intense feeding only lasts about three to four months. Blue whales, like most baleen species, pack in roughly 83% of the calories they need for the entire year during just 90 to 120 days of peak feeding. The rest of the year, they eat far less or barely eat at all.
Fasting for Months During Migration
Most baleen whales split their year between cold, food-rich waters in summer and warm breeding grounds in winter. Humpback whales, for example, spend late spring through autumn gorging at high-latitude feeding sites, then migrate thousands of miles to tropical waters to breed and give birth. During that migration and breeding period, they largely stop eating for over six months, surviving entirely on stored body fat in their blubber.
This means the feeding season is a matter of survival. Humpback whales expend about twice as much energy on the feeding grounds compared to the breeding grounds, burning through calories rapidly while also building the fat reserves that will carry them through half a year without food. Every feeding dive counts.
Bubble Net Feeding
One of the most remarkable hunting strategies in the animal kingdom belongs to humpback whales. Bubble net feeding is a cooperative technique that requires at least two whales working together, though groups can be much larger. The whales dive deep below a school of fish, then one whale, usually the leader, blows streams of bubbles from its blowhole while swimming in upward spirals. The rising wall of bubbles acts like a net, stunning and trapping the fish in an ever-tightening column near the surface.
The other whales swim in coordinated spiral patterns around the fish to keep them contained. As the group reaches the surface, they open their enormous mouths and lunge upward through the concentrated ball of prey, gulping thousands of fish in a single pass. The whole sequence requires precise communication and timing, a sign of the high social intelligence these animals possess.
Toothed Whales: Hunters of the Deep
There are over 80 species of toothed whales, a group that includes sperm whales, dolphins, porpoises, pilot whales, and beaked whales. These whales catch prey individually, either grabbing and biting or using suction to pull food into their mouths. Their primary targets are fish and squid.
Sperm whales are the most dramatic hunters of the group. They dive to extraordinary depths to find squid and octopuses, and stomach analysis tells us just how varied their diet is. Researchers examining three sperm whales stranded in the Bay of Biscay recovered hundreds of beaks from 19 separate species of cephalopods, including giant squid, the seven-arm octopus (the world’s largest octopus), and the vampire squid. Chemical analysis of those beaks revealed that the giant squid lives in the deepest waters of any species found, and the largest squid species tend to dwell closest to the ocean floor, meaning sperm whales are hunting across multiple depth zones during their dives.
Orcas: Specialists With Regional Tastes
Killer whales are technically the largest dolphin species, but their diet sets them apart from every other toothed whale. They are apex predators that eat fish, squid, seals, seabirds, and even other whales far larger than themselves.
What makes orcas unusual is how dramatically their diets vary by population. In the northeastern Pacific, three partially overlapping populations of “resident” killer whales feed primarily on salmon. Southern resident killer whales depend heavily on Chinook salmon from March through August, then shift to coho salmon in September and chum salmon from October through December. Southern Alaska residents eat a greater proportion of chum salmon throughout the summer, along with small but meaningful amounts of Pacific halibut and arrowtooth flounder.
Even individual pods within these populations show distinct preferences. Some pods switch from Chinook to sablefish in late autumn, while others favor halibut during the non-summer months. These aren’t random choices. Different pods forage in different areas and at different times, and their diets reflect the prey available in their specific ranges. Other orca ecotypes around the world specialize in marine mammals, with some populations targeting seals and others coordinating attacks on baleen whale calves.
How Whale Calves Feed
Newborn whales don’t eat krill or fish. Like all mammals, they nurse. Whale milk is extraordinarily rich, with a fat content of 30 to 50% (compared to about 4% in human milk). This thick, almost toothpaste-like consistency helps calves gain hundreds of pounds per day during their first months of life, rapidly building the blubber layer they need to survive in cold ocean water.
For baleen whale mothers, nursing is especially demanding because it typically happens during the fasting period on the breeding grounds. A humpback mother, for instance, produces massive quantities of high-fat milk for her calf while eating little to nothing herself, drawing entirely on the energy reserves she built up during the previous summer’s feeding season. By the time she migrates back to colder waters with her calf, she may have lost a third of her body weight.