Baleen whale modern mysticetes are obligate filter feeders, using their baleen to strain small prey items (including small fish, krill, copepods, and zooplankton) from seawater. Despite their carnivorous diet, a 2015 study revealed they house gut flora similar to that of terrestrial herbivores. Different kinds of prey are found in different abundances depending on location, and each type of whale is adapted to a specialized way of foraging. There are two types of feeding behaviors: skim-feeding and lunge-feeding, but some species do both depending on the type and amount of food. Lunge-feeders feed primarily on euphausiids (krill), though some smaller lunge feeders
Baleen whale dislodge parasites. Some species of barnacle, such as "Conchoderma auritum" and whale barnacles, attach to the baleen plates, though this seldom occurs. A species of copepod, "Balaenophilus unisetus", inhabits baleen plates of whales in tropical waters. A species of Antarctic diatom, "Cocconeis ceticola", forms a film on the skin, which takes a month to develop; this film causes minor damage to the skin. They are also plagued by internal parasites such as stomach worms, cestodes, nematodes, liver flukes, and acanthocephalans. Before reaching adulthood, baleen whales grow at an extraordinary rate. In the blue whale, the largest species, the fetus grows