Whales, like all mammals, nourish their young with milk. While this might seem challenging underwater, whales have evolved remarkable adaptations to ensure their calves receive sustenance. Their unique nursing methods and specialized milk composition are crucial for rapid growth and survival in the marine environment.
How Whales Nurse Their Calves
Whales nurse their calves through a specialized process. Female whales possess mammary glands located within slits on either side of their genital slit, near the tail. These nipples are inverted and only become apparent when the calf is ready to feed. When a calf is ready to nurse, it nudges the mother’s mammary area, signaling her to release the nipples from their protective slits.
Unlike land mammals, whale calves do not suckle in the traditional sense because they lack lips for creating suction and would otherwise ingest too much seawater. Instead, the mother whale ejects thick milk into the calf’s mouth using muscular contractions around her mammary glands. The calf may position its tongue into a U-shape or curl it into a tube to help channel the milk and minimize spillage. This process occurs in short bursts, with nursing events for humpback whales averaging around 23 seconds. Calves roll to the side during feeding, and the mother aligns herself to facilitate the process.
The Nutritional Power of Whale Milk
Whale milk is exceptionally rich and dense, enabling rapid growth and blubber development in calves. Its composition features a high fat content, ranging from 30% to 50%, significantly higher than cow’s milk (around 3-4%) or human milk. This high fat concentration gives whale milk a thick, creamy consistency, compared to toothpaste or melted ice cream, preventing it from dissolving easily in the surrounding seawater.
Beyond its high fat content, whale milk is also rich in protein, between 9% and 15%, providing essential building blocks for muscle and bone development. The low water content, between 40% and 53%, further contributes to its energy density. This nutrient-packed milk helps calves quickly develop a thick layer of blubber, providing insulation against cold ocean waters and serving as an energy reserve. For instance, a blue whale calf can gain up to 100 kilograms (about 220 pounds) per day due to the caloric intake from its mother’s milk, which can be around 200 liters daily. This rapid growth is important for species that undertake long migrations, as calves need to build strength and blubber reserves quickly.