The blue whale is commonly referred to as simply "blue whale." It is the largest animal known to have ever existed, growing up to 100 feet long and weighing as much as 200 tons or more. Known scientifically as Balaenoptera musculus, the blue whale is a marine mammal that primarily feeds on small shrimp-like animals called krill. Blue whales are notable for their distinctive blue-gray coloration, which can appear mottled, and their massive size makes them a symbol of the ocean's grandeur. They are currently listed as endangered due to historic whaling practices and habitat loss.