Toothed whale brain size with the expected brain size based on such allometric analysis provides an encephalisation quotient that can be used as another indication of animal intelligence. Sperm whales have the largest brain mass of any animal on earth, averaging and in mature males, in comparison to the average human brain which averages in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. Dolphins are known to engage in complex play behaviour, which includes such things as producing stable underwater toroidal air-core vortex rings or "bubble rings". Two main
Fin whale for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU). Fin whale The fin whale ("Balaenoptera physalus"), also known as finback whale or common rorqual and formerly known as herring whale or razorback whale, is a marine mammal belonging to the parvorder of baleen whales. It is the second-largest species on Earth after the blue whale. The largest reportedly grow to long with a maximum confirmed length of , a maximum recorded weight of nearly , and a maximum estimated weight of around . American naturalist Roy Chapman Andrews called the fin whale "the