A baby blue whale gains about 200 pounds during its first day after birth. In fact, the young whale maintains this daily weight gain throughout its entire first year of life by feeding exclusively on its mother's milk. Each day the newborn also grows about one inch longer.
Blue whales become sexually mature between five and 10 years of age. A female blue whale is pregnant for almost one year before she gives birth to a three-ton, 25-foot long baby. To feed this newcomer, the mother makes over 50 gallons of milk daily. Females typically produce offspring every two to three years.