Whales, like all mammals, feed their young milk. This process is crucial for calf survival and rapid development, despite unique underwater challenges. This system allows calves to quickly build blubber for insulation and buoyancy in cold ocean waters.
The Unique Act of Nursing Underwater
Nursing underwater requires specialized adaptations for both the mother and the calf. Unlike land mammals, whale mothers have nipples concealed within mammary slits on their underside, near the genital area. When the calf is ready to feed, it nudges the mother’s belly, signaling its readiness. This stimulation causes the nipples to become accessible, and the mother then actively ejects milk directly into the calf’s mouth.
Whale calves do not possess lips to create suction like many land mammals. Instead, they have evolved specialized mouth structures, such as the ability to curl their tongues into a tube or “taco” shape, to channel the rich milk and prevent it from dispersing into the surrounding water. This “injection” method, coupled with the calf’s precise positioning, often alongside or beneath the mother, ensures efficient delivery of the thick milk. Nursing sessions are typically brief, lasting only seconds to a couple of minutes, but occur frequently throughout the day and night to provide continuous nourishment.
The Nutritional Power of Whale Milk
Whale milk is exceptionally rich and concentrated, supporting rapid growth and blubber accumulation in cold ocean environments. Its composition varies by species but generally boasts a very high fat content, often ranging from 30% to 50%, and in some cases, even up to 60%. This is significantly higher than the milk of terrestrial mammals, which typically contains 3-5% fat. The high fat content provides the immense energy required for calves to gain weight quickly; for instance, a blue whale calf can gain about 90 kilograms (200 pounds) per day.
Beyond fat, whale milk also contains a substantial amount of protein, typically between 8% and 15%, and has a very low water content compared to cow or human milk. This thick, creamy consistency, often compared to yogurt or toothpaste, prevents the milk from diluting in the seawater during feeding. This nutrient-dense formula allows calves to develop a thick blubber layer for thermoregulation and buoyancy in their marine habitat.
Growth and Development: From Milk to Solid Food
The initial period of milk-feeding supports the calf’s rapid growth, immune system, and blubber reserves. The duration of nursing varies considerably among whale species, ranging from several months to several years. For example, baleen whale calves, such as humpbacks, might nurse for about 7 to 11 months, while some toothed whales, like sperm whales, can continue nursing for 4 to 5 years, or even longer.
As calves mature, they gradually transition from a milk-exclusive diet to solid food. This transition often involves the mother teaching the calf essential foraging and hunting skills. For baleen whales, this might mean learning to filter feed on krill or small fish, while toothed whales learn to hunt larger prey like fish or squid. Even after beginning to consume solid food, some calves may continue to nurse, gradually decreasing their reliance on their mother’s milk as they become more independent and capable hunters. This extended period of maternal care supports the calf’s overall survival and integration into its marine environment.