Whales are diverse marine mammals inhabiting oceans worldwide. Their diets vary considerably, influenced by species, habitat, and prey availability. Understanding what these creatures consume provides insight into their ecological roles and the intricate balance of marine ecosystems.
Dietary Categories: Baleen Whales
Baleen whales (Mysticetes) use baleen plates instead of teeth to filter feed. These keratin plates hang from their upper jaw and strain small organisms from large volumes of water. Blue whales, the largest animals on Earth, primarily consume krill, often eating up to four tonnes daily. They employ lunge feeding, rapidly swimming into dense swarms of krill with open mouths. After engulfing water, the whale expels it through the baleen plates, trapping krill for swallowing.
Humpback whales also feed on krill and small schooling fish like herring and anchovies. Humpbacks exhibit various feeding strategies, including “bubble-net feeding” where groups of whales cooperatively blow bubbles in a circular pattern, creating a “net” to herd fish or krill before surging through the concentrated prey. Some humpbacks also use “flick feeding,” lashing their tails to disorient prey, or “trap feeding,” floating vertically with open mouths to funnel food.
Dietary Categories: Toothed Whales
Toothed whales (Odontocetes) possess teeth and are active predators, hunting individually or in groups. Their diets primarily consist of fish and squid; some larger species also prey on marine mammals. They use echolocation to locate prey in dark or deep waters, emitting sounds that provide information about prey size, shape, location, and movement.
Orcas, also known as killer whales, are apex predators with a highly varied diet, consuming fish, squid, and even other marine mammals such as seals, sea lions, and occasionally other whales. Their hunting techniques can be highly specialized and passed down through generations within family pods. Sperm whales, the largest toothed whales, primarily dive to great depths to hunt for squid, including giant and colossal squid. Dolphins exhibit diverse feeding methods, including cooperative hunting where they herd schools of fish into a tight “bait ball” before taking turns to feed.
Diversity in Diet and Feeding Strategies
Beyond the primary categories, some whales exhibit highly specialized diets and unique feeding behaviors that allow them to thrive in specific environments. Gray whales, for instance, are unique among baleen whales for their bottom-feeding strategy. They typically roll onto their side and suction up sediment from the seafloor, filtering out small invertebrates through their coarse baleen plates. This action often leaves behind characteristic oblong pits on the ocean floor.
Narwhals, known for their long tusks, have a restricted diet, focusing on Greenland halibut, polar and Arctic cod, and Gonatus squid. They feed near the ocean bottom in deep waters, creating suction with their mouths to capture prey. This specialized diet means narwhals are highly dependent on the availability of these specific prey items found in their cold Arctic habitats, influencing their seasonal movements and survival. The varied and complex feeding strategies across whale species underscore their adaptability to diverse marine food sources.