Dolphins, like all mammals, feed their young milk, a process that occurs entirely underwater. This highlights their specialized biology and adaptations for aquatic life. Unlike land mammals, dolphin mothers and their calves navigate the unique challenges of nursing in a marine environment, relying on precise actions and a highly concentrated milk composition to ensure the calf’s rapid growth and survival.
Unique Nursing Adaptations
Dolphin mothers possess specialized mammary glands concealed within abdominal slits on their underside, rather than external nipples. When a calf is ready to feed, it nudges the area around these slits, stimulating the mother to expose her teats. The calf then positions its mouth into the slit and forms a watertight seal around the teat. This seal is achieved by curling its tongue into a cone or straw-like shape, sometimes utilizing small, finger-like projections on the sides of the tongue to prevent seawater from entering its mouth during feeding.
The mother dolphin has voluntary control over milk ejection, actively squirting thick, paste-like milk directly into the calf’s mouth, a process known as “let-down.” This controlled release ensures that milk is not lost into the surrounding water. Nursing sessions are brief, lasting about 5 to 10 seconds, but occur frequently. To facilitate nursing, the mother may slow her swimming speed or even lie on her side in the initial weeks, while the calf learns to angle itself for feeding.
Composition and Purpose of Dolphin Milk
Dolphin milk differs significantly from human or cow milk, being rich in fat and protein, and lower in water content. Its fat content can range from 30% to 50%, and protein levels are also high. This concentrated composition provides substantial energy and nutrients, important for the rapid growth and development of the calf in the cold ocean environment.
The high fat content is important for helping the newborn calf quickly develop a thick layer of blubber. This blubber serves as insulation, helping the calf maintain a stable body temperature in cool waters, as they are born without a pre-existing thick insulating layer. The protein in the milk supports the development of muscles, organs, and the immune system. The milk also has low lactose levels, distinct from many terrestrial mammals, reflecting adaptations to their aquatic diet and environment.
Calf Development and Weaning
Dolphin calves are highly dependent on their mothers for nutrition and protection during their early lives. Nursing periods vary by species, but bottlenose dolphins nurse for 18 to 24 months, sometimes extending up to three years or more. In the first few months, the calf relies almost entirely on its mother’s milk for sustenance.
Around three to four months of age, calves begin to develop teeth and may start experimenting with solid food, such as small fish. The transition from milk to a fully solid diet is gradual and can take anywhere from 18 months to three years. During this extended nursing period, calves also learn survival skills by observing and imitating their mothers and other pod members, including hunting techniques, navigation, communication, and social behaviors. The mother-calf bond remains strong for several years after weaning, supporting the calf’s integration into the pod and its ability to thrive independently.