Reproductive behavior is known mostly from studies on captive individuals, primarily the bottle-nose dolphin. Copulation normally occurs during the spring months, with the male-female pair exhibiting courtship for some time prior to copulation. Gestation in the species studied is between 11 and 12 months, after which a single calf is produced. Delivery is normally tail first, and the newborn is capable of swimming and breathing within the first minutes. Some mothers have been observed raising the calf to the surface, as if to help it, but dolphins apparently play in this fashion with a variety of objects, living or not. Such play may have provoked the stories of drowning persons being helped to shore by dolphins.

After birth, the calf follows its mother closely, and suckling takes place frequently, with the mother rolling slightly and the calf nuzzling the mammary area. The dolphin's two mammary glands open into a pair of sacs on either side of the anal opening, and the calf's beak fits into the openings of the sacs. The nipple is grasped between the upper jaw and the tongue, and muscular contractions by the mother literally squirt milk into the calf's mouth. Nursing may continue for as long as 12 to 18 months after birth, although weaning is probably slowed or inhibited in captive animals.

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