Dolphins are marine mammals; their young, called calves, are born live and are fully dependent on the mother for nourishment and protection. Because a calf is born into an aquatic environment and is expected to grow rapidly, its dietary needs are unique compared to land-based species. The journey from complete dependence on maternal nutrition to becoming a self-sufficient hunter is essential for the young dolphin.
The Unique Composition of Dolphin Milk
The initial and only food source for a calf is milk, which is specially formulated to meet the demands of underwater life and rapid growth. Dolphin milk possesses an extremely high-fat content, often ranging from 33% to over 40% fat, making it significantly richer than the milk of most terrestrial mammals. This high caloric density provides the massive energy boost necessary for the calf to develop a thick layer of blubber, which is needed for insulation in the cold ocean environment.
The milk’s composition also features a high protein concentration but a notably low level of lactose, the sugar found in the milk of land mammals. This difference in sugar content is an adaptation to the marine lifestyle. The calf lacks the muscular lips necessary to latch onto a nipple like a terrestrial mammal, requiring a unique nursing method.
The mother dolphin has her mammary glands concealed within specialized slits on her abdomen to maintain a streamlined body shape. When the calf is ready to feed, it positions its beak into the slit, which stimulates the mother to voluntarily eject or “squirt” the thick, paste-like milk directly into the calf’s mouth. This rapid squirt-feeding method is necessary because both mother and calf must surface frequently to breathe, necessitating a highly efficient transfer of nutrients.
The Duration of Nursing and Weaning
The period of reliance on the mother’s milk is lengthy, reflecting the substantial maternal investment required to raise a calf in the ocean. For many species, including the common Bottlenose dolphin, nursing typically lasts between 18 months and two years. However, the exact duration can vary based on species and environmental factors, such as the availability of prey in their habitat.
The weaning process is defined as the gradual shift away from milk dependency, but it does not mean the calf is suddenly independent. Even after a calf begins to sample solid food, it continues to nurse for many months or even years as a supplement to its diet.
This extended period of dependence ensures the calf receives continuous, high-quality nutrition while its body and skills develop. The long nursing phase is also a reflection of the complex cognitive and social skills the young dolphin must acquire before it can survive on its own.
Transitioning to a Hunter’s Diet
The transition from a purely milk-based diet to a predatory one begins surprisingly early, often when the calf is only a few months old. At this stage, the mother introduces small, easily managed prey items, such as tiny fish, squid, or various crustaceans. These first solid food items are often captured and presented to the calf by the mother herself.
The initial consumption of solid food is more about learning and practice than fulfilling a major nutritional requirement, which is still met by the high-fat milk. Calves learn to hunt primarily by observing and mimicking their mothers, a form of vertical social transmission.
They closely follow the mother through the water, watching as she employs various foraging techniques, such as herding fish or using specific environmental features to trap prey. As they mature, calves begin to practice these skills, sometimes using simple techniques like “snacking,” where they trap small fish against the water’s surface. This multi-faceted learning process is what ultimately prepares the young dolphin to transition into an independent, successful hunter.