Digestive system of humpback whales stretching like an accordion. They allow whales to open their mandible to 90 degrees to gulp water and prey. They expel saltwater through the baleen plates, leaving behind krill and plankton. The whale's tongue plays a vital role in filter feeding, as it is used to push the water out of its mouth while keeping the prey trapped in its baleen bristles. As humpback whales do not have teeth, their food is swallowed whole and travels down the esophagus into the preliminary stomach (known as the forestomach) to be ground. Baleen whales have a multi-chambered stomach, divided into three distinct
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