Blue whale facts are the largest mammals on Earth. They can grow up to 100 feet long and weigh over 200 tons. Their diet consists mainly of tiny shrimp-like creatures called krill. Blue whales communicate using low-frequency sounds that can travel long distances. They have a lifespan of about 70-90 years. Despite their size, they feed on some of the smallest organisms in the ocean. Their population is estimated to be between 10,000 and 25,000 individuals.