The Right Whales (Eubalaena) are among the largest baleen whales. These marine mammals are characterized by their massive size, highly arched upper jaw, and lack of a dorsal fin. Their survival depends on a specialized, energy-intensive feeding strategy that targets some of the ocean’s smallest organisms. This approach defines their behavior, migration patterns, and overall health.
The Primary Menu: Specialized Zooplankton Prey
The diet of Right Whales is specific, focusing almost entirely on zooplankton, which are small, drifting animals. The North Atlantic Right Whale relies heavily on the calanoid copepod, Calanus finmarchicus. This minute crustacean is the cornerstone of their diet, providing the high-calorie, lipid-rich fuel necessary for their massive bodies.
These tiny prey measure between 0.5 and 3.5 millimeters in length. The whales must seek out incredibly dense aggregations of these small organisms to make feeding energetically worthwhile. While Calanus finmarchicus is the primary target, Right Whales also consume other small invertebrates, including other copepod species, krill, and small amphipods.
The nutritional quality of zooplankton directly relates to the whale’s health and reproductive success. Copepods in areas like the southern Gulf of St. Lawrence are often larger and more lipid-rich than those in the Gulf of Maine. This higher energy content makes certain feeding grounds more attractive, especially for pregnant or lactating females with high energetic demands. The reliance on small, aggregated prey makes the whales vulnerable to changes in ocean conditions that affect zooplankton distribution and abundance.
Skim Feeding: The Mechanics of Baleen Filtration
Right Whales employ “skim feeding” to efficiently harvest their prey. This technique involves swimming slowly with their mouths open, allowing water containing zooplankton to flow continuously into the oral cavity. The water is then filtered through hundreds of long, fine baleen plates that hang from the upper jaw, acting as a sieve.
These baleen plates are made of keratin and can reach lengths of up to eight feet. The inner edge of each plate is frayed into a dense, fibrous mesh that traps the copepods as the water passes out. The whale then uses its tongue to scrape the accumulated prey from the mesh and swallow it.
The anatomical adaptations for skim feeding include a highly arched rostrum that accommodates the long baleen plates. This feeding style contrasts sharply with the “lunge feeding” used by rorqual whales, such as Humpbacks. Rorquals rapidly engulf huge volumes of water and prey using expandable throat pleats, while Right Whales rely on the continuous, slow-motion straining action of their specialized baleen.
Energy Requirements and Critical Feeding Grounds
The sheer size of a Right Whale necessitates an immense daily caloric intake, requiring extremely dense patches of zooplankton. A single adult Right Whale must consume staggering amounts of prey, estimated at over one ton (2,000 pounds) of copepods per day during peak feeding season. This quantity equates to ingesting billions of individual copepods.
Locating these rich food sources dictates the whale’s annual migration patterns to seasonal feeding grounds. Significant areas include the Gulf of Maine, the Bay of Fundy, and the Gulf of St. Lawrence, where prey aggregates in high concentrations. The whales must feed intensively in these northern areas throughout the spring, summer, and fall to build up thick layers of blubber.
This stored energy sustains them through their long, non-feeding migrations to calving grounds off the southeastern United States during the winter. Lactating females have the highest energetic demands, requiring the most food to support their size and the rapid growth of their calves. A poor feeding season due to insufficient prey density can lead to nutritional stress, impacting their ability to reproduce and survive.