How Baby Whales Nurse
Baby whales, known as calves, nurse underwater, a process adapted for their aquatic lives. Mother whales possess specialized mammary glands concealed within slits on their underside, near the tail. These mammary slits protect the nipples and are inverted for hydrodynamic efficiency. When a calf is ready to feed, it nudges the mother’s belly, prompting the nipples to become exposed.
Unlike land mammals, whale calves do not have lips to create suction. Instead, the mother whale injects the milk directly into the calf’s mouth. This injection is achieved by the mother contracting specialized muscles surrounding her mammary glands. The calf adapts by curling its tongue into a tube-like or U-shape, which helps channel the milk and prevents seawater from entering its mouth. Nursing sessions are brief, lasting 5 to 10 seconds, but occur frequently throughout the day.
What Makes Whale Milk Unique
Whale milk has properties tailored for rapid growth and survival in cold ocean environments. It is rich in fat, with concentrations typically ranging from 30% to 50%, and in some species, reaching 53%. This high fat content gives whale milk a thick, almost toothpaste-like consistency, which prevents it from dispersing into the surrounding seawater during feeding.
The milk also contains high protein, often between 9% and 15%, and has low water content compared to terrestrial mammal milk. These concentrated nutrients fuel the calf’s rapid development. The fat directly supports the swift accumulation of a thick blubber layer, important for insulation against cold ocean temperatures and for providing energy reserves.
The Journey from Nursing to Independence
The nursing period for whale calves varies significantly across species. Baleen whale calves, such as humpbacks, nurse for a shorter duration, often ranging from 4 to 11 months. In contrast, toothed whale calves, including killer whales and belugas, nurse for a longer period, lasting from one to three years.
The rich milk allows calves to grow rapidly. For example, a blue whale calf can gain up to 80 to 100 kilograms (approximately 200 pounds) per day. This rapid weight gain is important for building blubber reserves.
As calves mature, they gradually transition from a milk-exclusive diet to consuming solid foods. While some species, like humpback calves, begin eating krill and small fish around seven months of age, many calves continue to nurse even after they start foraging independently.