Whales, as fully aquatic mammals, have developed highly specialized behaviors and unique biological adaptations to ensure their young, or calves, are fed in an underwater environment. The process of nursing is a logistical marvel and a demonstration of the profound evolutionary changes that allow these enormous animals to sustain their lineage entirely at sea. The mechanics of this maternal care are crucial for the calf’s survival and rapid growth in the challenging conditions of the ocean.
Whales are Mammals
Baby whales drink milk because they belong to the class Mammalia, defined by the presence of mammary glands and the production of milk to feed their young. Whales are members of the order Cetacea, including both baleen whales (Mysticeti) and toothed whales (Odontoceti). This classification confirms they share the biological necessity of lactation with terrestrial mammals. They are warm-blooded, breathe air through lungs, and give birth to live young, making nursing a requirement for the newborn calf’s survival. Calves begin nursing shortly after birth in warm, shallow waters.
The Mechanics of Underwater Nursing
Nursing underwater presents a significant challenge, solved through specialized anatomy and coordinated action. The mother whale does not have externally visible nipples, which would create drag. Instead, her mammary glands are protected within folds of skin called mammary slits on her abdomen. When the calf is ready to feed, it nudges the area, stimulating the mother to extend the nipple from the slit.
The calf cannot suckle like a land mammal because it lacks the necessary lips and facial structure to create suction in water. To overcome this, the mother uses powerful muscular contractions to forcibly inject or squirt the milk directly into the calf’s mouth. This ejection minimizes the time water has to dilute the nutrient supply. The calf often curls its tongue into a U-shape, which helps channel the milk past its throat and prevents the inhalation of seawater. The entire process is quick and efficient, ensuring the calf receives a high volume of milk during each brief nursing session.
The Unique Composition of Whale Milk
The milk produced by female whales differs significantly from that of terrestrial mammals, reflecting the demands of the aquatic environment. It has a high-fat content, typically ranging between 35% and 50% depending on the species. This contrasts sharply with cow’s milk, which contains only about 3% to 4% fat. This high concentration gives the milk a consistency similar to toothpaste or soft cheese, preventing it from dissolving quickly into the surrounding seawater.
This concentrated energy source is necessary for the calf to rapidly develop a thick, insulating layer of blubber. Blubber is required for thermoregulation in cold ocean waters, as water conducts heat away from the body faster than air. Whale milk also has low water and sugar content, making it nutrient-dense. This formulation fuels the high growth rates seen in young whales; for instance, a Blue Whale calf can gain an estimated 200 pounds of body mass daily.
Weaning and Rapid Development
The concentrated nutrition of the milk supports a period of rapid growth. For species like the North Atlantic Right Whale, calves can more than double their size during the nursing period, gaining about 75 pounds per day. The duration of this intense nursing period varies significantly between species. Some humpback whale calves are weaned in as little as five to seven months, while a sperm whale calf may continue to nurse for up to two years or more.
The transition from a purely milk-based diet to solid food is a gradual process that culminates in weaning. During this time, the calf begins to experiment with the primary food source of its species, such as krill, fish, or squid. Achieving this rapid growth in early life is vital. It provides the size, strength, and blubber insulation needed to survive their first major migration and become independent in the open ocean.