The largest mammal living in the ocean is the blue whale (*Balaenoptera musculus*). Adult blue whales can reach lengths of up to 100 feet (30 meters) and weigh as much as 200 tons or more, making them the largest animals known to have ever existed on Earth. They are filter feeders, primarily consuming tiny shrimp-like animals called krill. Blue whales have a heart that can weigh as much as a small car and are often found in oceans worldwide, migrating between feeding and breeding grounds. Their impressive size and unique songs make them a fascinating subject of study and conservation efforts.