The blue whale is the largest animal on Earth, reaching lengths of up to 100 feet and weights of over 200 tons. They are primarily found in the open ocean and can be found in all of the world’s oceans. Blue whales feed on tiny shrimp-like animals called krill, eating up to 4 tons of krill per day. They are known for their vocalizations, which are the loudest of any animal and can be heard for hundreds of miles under water. Blue whales were heavily hunted during the 20th century, causing their population to decline significantly. Today, they are protected by international law and their numbers are slowly increasing, but they are still considered an endangered species.