Dolphins, marine mammals, breastfeed their young, a process that raises questions about how it’s possible underwater. Their unique adaptations allow them to nourish calves efficiently beneath the surface.
The Unique Process of Dolphin Nursing
Female dolphins possess specialized mammary glands located internally within mammary slits on their underside, which helps maintain their streamlined body shape. Their nipples are inverted and protected within these slits, emerging only when stimulated. When a calf is ready to feed, it positions its beak into the slit and curls its tongue into a “straw-like” or “cone” shape, forming a tight seal around the nipple. This specialized tongue structure prevents seawater from entering the calf’s mouth during nursing.
The mother dolphin does not rely on the calf’s sucking action. Instead, she voluntarily squirts streams of milk directly into the calf’s mouth using muscle contractions around her mammary glands. This active ejection mechanism ensures milk is delivered rapidly and without significant dilution by the surrounding water. Nursing sessions are brief, lasting only a few seconds each time, but they occur with high frequency, sometimes as often as four times per hour during the calf’s first week of life. Initially, the mother may slow her swimming speed or even lie on her side to facilitate nursing.
The Composition and Importance of Dolphin Milk
Dolphin milk has a distinct composition compared to that of terrestrial mammals, being rich and fatty. Its fat content ranges from 16% to 46%, significantly higher than human or cow milk, and it also contains high protein levels while having a low water content. This energy-dense milk is important for rapid growth and development of the calf.
The rich milk facilitates the accumulation of a thick blubber layer beneath the calf’s skin. This blubber serves multiple purposes: it provides insulation from cold ocean temperatures and acts as an energy reserve. It also contributes to buoyancy, helping the young calf conserve energy while navigating the water. Dolphin milk also plays a role in immune protection, as it transfers antibodies from the mother to the calf, providing passive immunity against marine pathogens.
Mother-Calf Bonding and Development
The nursing period in dolphins extends for a considerable duration, lasting between one and three years. This prolonged period of dependency is important for the calf’s overall development, extending beyond just nutritional intake. During this time, the calf remains in close proximity to its mother, often swimming within her “slipstream” or hydrodynamic wake, which reduces the energy the calf expends while swimming.
This close association allows the calf to learn survival skills by observing and imitating its mother and other pod members. These learned behaviors include foraging techniques, navigation within their environment, and how to avoid potential dangers. The strong mother-calf bond fostered through nursing and constant interaction also plays a significant role in the calf’s social development and its integration into the dynamics of the dolphin pod.