Filter feeder gap between the two rows of baleen plates lets the water in together with the prey, while the baleens filter out the water. Rorquals such as the blue whale, in contrast, have smaller heads, are fast swimmers with short and broad baleen plates. To catch prey, they widely open their lower jaw — almost 90° — swim through a swarm gulping, while lowering their tongue so that the head's ventral grooves expand and vastly increase the amount of water taken in. Baleen whales typically eat krill in polar or subpolar waters during summers, but can also take schooling fish, especially
Baleen whale of the world, necessitating more efficiency traveling over long distances between widely distributed prey sources which also resulted in a lower metabolic rate, and feeding on baitballs. A 2017 analysis of body size based on data from the fossil record and modern mysticetes indicates that the evolution of gigantism in baleen whales is a recent phenomenon, estimated to have occurred within the past 3.1 Ma. Before 4.5 million years ago, few mysticetes exceeded 10 meters (33 feet) in length; the two largest miocene species were less than 13 m in length. The initial evolution of baleen and filter feeding long