How Do Dolphins Nurse?
Dolphins are fascinating, intelligent creatures that are well adapted to their life in the seas. Although they are similar in appearance to fish, they are actually mammals that give birth to fully formed offspring, which they nurse with milk from the female dolphin's mammary glands. But how can an infant dolphin nurse underwater, since it does not have flexible lips like most mammals that live on land? How does the dolphin's milk keep from getting diluted by the salt water?
A dolphin gives birth only after the baby has developed in the womb for a full year. Soon after the baby dolphin or calf is born into open water, it is helped by its mother to the surface to breathe. After resting a little, the calf, guided by instinct, seeks one of the two nipples that are hidden inside of slits on the mother's underbelly. When the dolphin is small, the mother rolls on her side to make it easier for the calf to nurse near the surface of the water. The calf nuzzles its snout or rostrum into the slit and feels for the nipple with its tongue.
When it finds its mother's nipple, the calf cups its tongue around the nipple and pushes it up against the roof of its mouth, forming a tight seal, and then presses its rostrum forward. The mother dolphin then responds by contracting muscles around the mammary glands that squirt the rich, thick, fatty milk in long squirts into the calf's mouth. Then nursing last for several seconds each time, and during the first few week of the calf's life, feedings take place about four times per hour. The dolphins grow very quickly on the milk, which is higher in calcium and nutrients than either cow's milk or human milk.
As the dolphin becomes older, it will nurse by swimming under the mother and approach at an angle as they both swim slowly forward. The dolphin calf usually continues to nurse for the first one or two years of its life, even for a while after it begins to eat fish. (Dolphins eat fish whole; after catching them with their peg-like teeth, they swallow them head-first.) Some dolphins nurse for even longer periods, and the mother dolphin will usually continue nursing the young dolphin until she becomes pregnant with another calf. Mother dolphins are very affectionate and attentive to their calves, leaving them only briefly to forage for fish, and keeping in contact with them by their echo-location, and their language of clicks and whistles.