The largest mammal species on Earth is the blue whale, scientifically known as Balaenoptera musculus. 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 to have ever existed. These immense marine mammals primarily feed on small shrimp-like creatures called krill, consuming up to 4 tons of krill daily during feeding seasons. Blue whales are known for their incredible vocalizations and play a vital role in marine ecosystems, as their feeding habits influence prey populations.