The blue whale is a baleen whale that is the largest of its kind and may be the largest animal that has ever swum in the earth's oceans. The longest blue whale ever caught was about 108 feet long and was caught by whalers in Antarctica. This particular whale was female and many of the larger types of these whales as well as many other species of whale are female. The Blue whale is also a very heavy animal that can weigh anywhere between 100-150 tons. When it comes to the mating habits of blue whales much research indicates that these whales reach sexual maturity at around 6-9 years old or when the males grow to about 75 feet and the females grow to around 80 feet in length. When the calves of the blue whale female are born they often come out weighing around 3 tons and are often 27 feet in length. In addition to this the calves are born at a period that spans ever 2-3 years and the gestation period is around 12 months for blue whales. The calves will live off of their mother's milk for at least 7 months and the female blue whale will wean them when they reach about 52 feet in length at which time they can weigh up to 23 tons.
When they are nursing many blue whale calves can drink 100 gallons or more of their mother's milk every day. This is a large amount that the female whale must be prepared for by eating excess krill and plankton while pregnant and after child birth. The calves gain around 200 pounds a day on this diet of fat rich milk and this translates into 8 pounds every hour. The calves will also grow about an inch a day during the 7 month period of nursing.