 Vitellogenesis (the formation of yolk within the ovary) occurs in the late summer, and is immediately followed by mating and fertilization in the fall, with the young being born the following spring to summer.The seasonality of these events means the reproductive cycle is offset by six months between populations in the Northern and Southern Hemispheres.The gestation period has been variously estimated at eight months off northeastern Brazil and 9–11 months off the southeastern United States.