Blue whale calves are the biggest babies on Earth, easily, and at birth already rank among the largest full-grown animals. They pop out at around 8,800 pounds (4,000 kg) with a length of some 26 feet (8 meters). They gain 200 pounds (90 kg) a day! Their growth rate is likely one of the fastest in the animal world, with a several billion-fold increase in tissue in the 18 months from conception to weaning.