The largest animal to have ever existed on Earth is the blue whale. These magnificent marine mammals can reach lengths of up to 100 feet (30 meters) or more and weigh as much as 200 tons or more. Blue whales are filter feeders and primarily consume small shrimp-like animals called krill, which they devour in massive quantities during feeding seasons. Their sheer size and majestic swimming style make blue whales an awe-inspiring sight in the oceans. Sadly, they were once driven to near extinction by whaling practices, but conservation efforts have helped their populations gradually recover in certain areas.