Baby whales, known as calves, begin their lives with an immediate need for energy and insulation in the cold marine environment. Like all mammals, the sole food source for a newborn calf is its mother’s milk. This diet fuels extremely rapid growth, which is necessary for the creature to quickly develop a thick layer of blubber for thermal regulation. A blue whale calf, for example, may gain up to 90 kilograms (200 pounds) per day during its initial nursing period.
The Uniqueness of Whale Milk Composition
Whale milk has a unique composition unlike the milk of any land mammal, reflecting the demands of life in the ocean. Its most striking characteristic is its extraordinary fat content, which can range from 30% to over 50% in some species, such as baleen whales. This is dramatically higher than the 3-5% fat found in human or cow milk.
The low water content and high concentration of fat and protein give the milk a thick, viscous consistency, often described as resembling soft cheese or toothpaste. This density is a physical adaptation that prevents the milk from dissolving too quickly into the surrounding seawater before the calf can ingest it. The rapid intake of this lipid-rich formula allows the calf to quickly deposit the dense layer of blubber required for insulation and energy storage.
Baleen whales (Mysticetes) produce milk with a higher fat content over a relatively short nursing period. Toothed whales (Odontocetes), such as dolphins and orcas, have milk that is slightly lower in fat—closer to 10-30%—but they nurse their young for a much longer duration. The protein content is also high, sometimes reaching 13% in fin whale milk, providing the building blocks for rapid muscle and skeletal growth.
The Mechanics and Duration of Nursing
Nursing for a whale calf is a dynamic and physically demanding process that must occur entirely underwater. The mother has two mammary slits, which conceal her nipples to maintain a streamlined body shape while swimming. When the calf is ready to feed, it nudges the area around these slits to signal the mother.
The calf cannot suckle effectively because it lacks the necessary facial muscles and lips to create a seal underwater. Instead, the mother actively and forcefully ejects the thick, concentrated milk directly into the calf’s mouth in a matter of seconds. Calves often position themselves in the “echelon” position, swimming close to the mother’s side, which helps them conserve energy by riding her slipstream.
The duration of nursing varies between the two major whale suborders. Many large baleen whales, like humpbacks and blue whales, nurse for a brief period of four to eleven months before they are weaned. Toothed whales exhibit an extended period of maternal care, often nursing their young for one to three years, reflecting a slower developmental timeline.
Transitioning to the Adult Diet
The shift from milk to solid food is a gradual process that coincides with the development of the calf’s specialized feeding structures. For toothed whale calves, this transition involves learning to hunt and use echolocation, a complex skill that requires prolonged observation and practice with their mother. The adult diet of these Odontocetes consists of actively pursued prey, such as various species of fish, squid, and even other marine mammals for apex predators like the orca.
The transition for baleen whale calves is a shift toward bulk filter feeding, which is facilitated by the development of their baleen plates. These plates, made of keratin, hang from the upper jaw and act like a sieve to strain tiny organisms from large volumes of seawater. Calves begin to consume small organisms like krill, copepods, and plankton as they are weaned from their mother’s milk.
The calf’s first solid meals are often observed while the mother is feeding, allowing the young whale to gradually incorporate filter-feeding behavior into its routine. This learning period is important, as the adult life of a baleen whale depends on its ability to efficiently consume these small prey to support its body size. The successful transition marks the end of their dependence on milk and the start of an adult feeding strategy.