Blue whales do not have teeth; instead, they have large plates consisting of baleen, which is similar in texture to fingernails. After swallowing an enormous amount of seawater, blue whales use the baleen plates as a sieve for straining krill as the seawater expels from the animal.
Blue whales are the largest animals on Earth, measuring up to 100 feet long and weighing as much as 200 tons or more. In a single day, an adult blue whale can ingest as much as 4 tons of krill. Scientists estimate that between 10,000 and 25,000 blue whales live in the world's oceans.