Blue whales engage in an extensive courtship process that culminates in mating. A female blue whale mates with multiple partners, increasing the chances of fertilization. Males become sexually mature between the ages of five to 10, while females give birth every two to three years.
Not much is known about the mating process of blue whales, but scientists have discovered evidence indicating that the threat of whaling has caused the intervals between mating to decrease.
A baby blue whale gestates for 10 to 11 months, and a female blue whale gives birth to only one calf at a time. Twins, while heard of, are very rare. At birth, the calf weighs approximately 4 tons and is roughly a third of the length of his mother. He grows an average of 1 inch per day and is fully weaned by seven or eight months.
An adult blue whale has no natural predators, but calves are vulnerable to killer whales and other large predators. To protect themselves, calves travel in pods of two to three, though adults have been known to travel in large groups of up to 60 whales. A blue whale may appear to be traveling alone, but it has a powerful voice that can travel hundreds of miles through water and allows him to stay in contact with the rest of his pod.