Dolphin Killer whales have the second largest brain mass of any animal on earth, next to the sperm whale. The brain to body mass ratio in some is second only to humans. Self-awareness is seen, by some, to be a sign of highly developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like meta-cognitive reasoning (thinking about thinking) that are typical of humans. Research in this field has suggested that cetaceans, among others, possess self-awareness. The most widely used test for self-awareness in animals is the mirror test in which a mirror
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