Biodiversity & Conservation

Maturity and longevity: exact age at maturation is unknown, but is though to be approximately 6 years. Males reach maturity at lengths of 2.2m, females at 2m (Kinze, 2002). The maximum age is thought to be 22 and 27 years for males females respectively (Klinowska, 1991; Nowak, 2003).
Segregation and differential mortality: mature males are infrequently observed in breeding groups, suggesting either the presence of all male groups, or possibly more likely based on the repective maximum age of the sexes, that males have a higher mortality rate (Klinowska, 1991). Segragation of immature and newly matured individuals from breeding groups has also been observed (Klinowska, 1991).
Reproduction: mating takes place in late summer, peaking in June - July, but may be any time between May August. Gestation lasts for 11 months, and calves are borne at 1.2m long weighing approximately 35 kg (Kinze, 2002). Nursing lasts for 18 months, and the calf leaves the mother at an age of 2 years (Nowak, 2003). Although it is likely that many females 'rest' for a year between pregnancies, giving birth every 2-3 years (Klinowska, 1991) (hence being assessed as Breeding areas: have been suggested to exist in parts of the North Sea and eastern North Atlantic, (Reeves et al. 1999).