The largest species of whale is the blue whale (Balaenoptera musculus). Blue whales are not only the largest whales but also the largest animals known to have ever existed on Earth. They can grow up to 100 feet long and weigh as much as 200 tons. These magnificent creatures are found in oceans around the world, primarily feeding on small shrimp-like animals called krill. Blue whales are known for their deep, low-frequency vocalizations, which can be heard over long distances in the ocean, and they play an important role in marine ecosystems.