In addition to respiration, cetaceans have developed and used surface behaviours for many other functions such as display, feeding and communication. All regularly observed members of the order Cetacea, including whales, dolphins and porpoises, show a range of surfacing behaviours. Cetacea is usually split into two suborders, Odontoceti and Mysticeti, based on the presence of teeth or baleen plates in adults respectively. However, when considering behaviour, Cetacea can be split into whales (cetaceans more than 10 m long such as sperm and most baleen whales) and dolphins and porpoises (all Odontocetes less than 10 m long including orca) as many behaviours are correlated with size. Although some behaviours such as spyhopping, logging and lobtailing occur in both groups, others such as bow riding or peduncle throws are exclusive to one or the other. It is these energetic behaviours that humans observe most frequently, which has resulted in a large amount of scientific literature on the subject and a popular tourism industry.