Bubble net feeding feed in a short amount of time. Humpback whales have a vertical throat roughly the size of a grapefruit. They cannot physically swallow anything larger than that. They are carnivores and primarily feed on small fish such as krill, juvenile salmon, and herring. They are also baleen whales, which means that they do not have teeth, so they must be able to eat things that they can swallow whole. They have several vertical grooves running down the length of their body so that they can hold large volumes of water and fish at one time. They feed for up to
Baleen whale selenensis" is the earliest mysticete, dating back to 37 to 33 million years ago (mya) in the Late Eocene, and, like other early toothed mysticetes, or "archaeomysticetes", "M. selenensis" had heterodont dentition used for suction feeding. Archaeomysticetes from the Oligocene are the Mammalodontidae ("Mammalodon" and "Janjucetus") from Australia. They were small with shortened rostra, and a primitive dental formula (). In baleen whales, it is thought that enlarged mouths adapted for suction feeding evolved before specializations for bulk filter feeding. In the toothed Oligocene mammalodontid "Janjucetus", the symphysis is short and the mouth enlarged, the rostrum is wide, and the