Dolphins, often mistaken for fish due to their aquatic habitat, are mammals that give birth to live young rather than laying eggs. This reproductive strategy is shared with most other mammals. Their evolutionary journey from land-dwelling ancestors led to adaptations allowing them to thrive entirely in marine environments.
Dolphins Give Live Birth
Dolphin births typically occur in the water, often with the calf emerging tail-first. This tail-first presentation helps reduce the risk of drowning, as it allows the calf to remain connected to the mother via the umbilical cord until its head is delivered and it can surface for its first breath. Once fully delivered, the mother nudges her newborn to the surface to ensure it takes its initial breath of air. Other dolphins in the pod may stay close to the new mother and calf, offering support and protection.
The delivery process can take a couple of hours. Newborn calves are between 3 to 4 feet long and weigh 25 to 40 pounds. Their dorsal fin and tail flukes are pliable at birth, gradually stiffening within a few hours to days.
Mammalian Traits of Dolphins
Dolphins possess several distinct traits that classify them as mammals. Like all mammals, they are warm-blooded, meaning they maintain a consistent internal body temperature regardless of the surrounding water temperature. They accomplish this through metabolic processes and a thick layer of blubber that provides insulation.
Unlike fish, dolphins breathe air using lungs and must regularly surface to do so. They have a blowhole on top of their heads, which acts as a nostril, allowing them to efficiently inhale and exhale. Although their bodies appear smooth, dolphins have hair, which falls out shortly after birth. Female dolphins also possess mammary glands and produce milk to nourish their young.
Life of a Dolphin Calf
Immediately after birth, a dolphin calf is highly dependent on its mother for nourishment and protection. Calves nurse underwater, suckling rich, fatty milk from mammary slits on the mother’s underside. Nursing occurs frequently for the first few weeks, and can continue for up to two years. This high-fat milk supports rapid growth and the development of blubber for insulation.
The bond between a mother and her calf is strong, often lasting several years, even after weaning. Calves initially swim in a “slipstream” position next to their mothers, which conserves energy and helps them keep pace with the pod. Through observation and play, calves learn survival skills from their mothers and other pod members, including hunting techniques, navigation, communication, and social behaviors. This extended period of maternal care and social learning is important for a calf’s successful development and integration into its community.