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
Killing of animals by crawling up the target's nose and eating the targets' brain. Most attacks happen in moist areas like ponds or lakes. In the middle is the blowfish ("fugu") that can kill animals with its toxic organs that contain tetrodotoxin. The largest animal killer is the blue whale, which is the largest animal on Earth. The blue whale mostly feeds on krill ("euphausiacea") which is a small, abundant crustacean. Blue whales are almost entirely killed by killer whales and by humans. Chimpanzees wage war against rival groups, killing rival males and eating the baby chimps. Ants also wage warfare on other