Distinct pairing with embrace (Ref. 205). Exhibit ovoviparity (aplacental viviparity), with embryos feeding on other ova produced by the mother (oophagy) after the yolk sac is absorbed (Ref. 50449). Estimated gestation period 12-36 months (Ref. 247, 1765, 9030, 88829); TL at birth estimated between 150-200 cm; mating thought to take place during early summer; a female giving birth to young captured in August in Norwegian waters (Ref. 5983). Over a study period of 5 years, courtship-like behaviour was observed off southwest England between May and July, always in surface waters along thermal fronts; because actual mating was not observed, this may occur in deeper water (Ref. 88831). A one-year resting period between pregnancies is thought to occur, resulting in a 2-4 year interval between litters (Ref. 9030, 1765, 88829). Only one pregnant female has been observed giving birth to a litter of 6 pups (Ref. 88830).