Whales, as mammals, nurse their young with milk, a process enabled by mammary glands. Despite living entirely in aquatic environments, these marine giants have evolved unique adaptations for nursing. This allows them to provide their calves with the rich nourishment necessary for rapid growth and development underwater.
Hidden Mammary Glands
Unlike many terrestrial mammals, whales do not have externally prominent breasts or nipples. Instead, their mammary glands are concealed within specialized folds of skin called mammary slits, located on the underside of the whale, near the genital region. This hidden placement serves a dual purpose for their aquatic lifestyle. It contributes to the whale’s hydrodynamic body shape, reducing drag and allowing for efficient movement through water.
These mammary slits also protect the sensitive glands and nipples from the harsh marine environment, including saltwater, potential injuries, and parasites. When not nursing, the nipples remain inverted within these slits, maintaining the whale’s streamlined form.
Underwater Nursing Techniques
Nursing underwater presents a unique challenge for whales, as calves cannot suckle in the traditional manner of land mammals. The process begins when the calf nudges the mother’s abdominal area, signaling its readiness to feed. This stimulation causes the mother’s inverted nipple to emerge from the mammary slit.
The mother whale then actively contracts muscles around her mammary glands to eject a stream of milk directly into the calf’s mouth. This milk ejection mechanism is used because whale calves lack the lips required for suction. Some whale calves may also curl their tongues into a “taco” shape or a tube to help channel the thick milk and prevent it from dispersing. Nursing bouts are short and frequent, lasting only a few seconds, but delivering a substantial amount of milk.
The Power of Whale Milk
Whale milk differs significantly from that of terrestrial mammals, adapted to meet the rapid growth and insulation needs of calves in cold ocean waters. It is rich in fat, typically ranging from 30% to 50%, much higher than cow’s milk (3-4% fat) or human milk (around 4% fat). This high fat concentration gives whale milk a thick, semi-solid consistency, often compared to toothpaste or soft cream cheese, which prevents it from dissolving in seawater during nursing.
Beyond its fat content, whale milk also contains high levels of protein, often exceeding 10%, supporting muscle and bone development. It is also low in water and lactose. This energy-dense composition fuels rapid growth rates; a blue whale calf, for example, can consume over 150 liters of milk daily and gain as much as 100 kilograms (220 pounds) per day, primarily building the thick blubber layer for insulation in its marine environment.