Ovoviviparous, with 21 to 28 young in a litter. Development of young in the uterus being sustained by a large supply of yolk. Females give birth in late spring and summer in waters off Florida. During courtship, a pair sometimes a triplet of adults engaged in synchronized parallel swimming. While on it, the male may grab one of the female's pectoral fins with his mouth which induces the female to pivot 90° and roll on her back on the bottom. Then the male inserts a clasper in her vent, and then roll on his back beside the female. Pair may break apart and depart rapidly after copulation or the male may remain motionless on the subtrate as if recovering from the mating bout (Ref. 49562). Not all attempts of males to copulate with a female nurse shark result in successful fertilization, females may employ avoidance by 'pivotting and rolling' to escape from male attention (Ref. 49562). Or females may 'lie on back' and rest motionless and rigidly on the substrate (Ref. 51113, 49562). On the contrary, females send signals of readiness to copulate with males by arching their body toward their male partner and cupping the pelvic fin (Ref. 51126, 49562). Male nurse sharks may mate with many females over several weeks (polygyny) and vice versa (polyandry) (Ref. 49562). Also Ref. 205.