Most B. bairdii reach sexual maturity when they are about 9.4 meters long for males and 10 meters long for females. They mate in mid-summer in warm waters near Japan and California. The gestation period is thought to be approximately ten months, though pregnancies of up to 17 months have been reported. Calves are born between late November and early May. A mother will usually produce one calf every three years. The average lifespan is about 70 years (Minasian,S.,K Balcomb, III and L Foster, 1984. Watson, L. 1981).

Breeding interval: A mother will usually produce one calf every three years.

Breeding season: They mate in mid-summer in warm waters near Japan and California.

Average number of offspring: 1.

Range gestation period: 17 (high) months.

Average gestation period: 10 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)

Sex: male: 2922 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 4383 days.