The blue-ring octopus is only about eight inches wide with its tentacles extended. It prefers shallow water near Australia and often lives under piers. It avoids humans. But if it must defend itself, this creature can deliver a bite that is fatal. The toxin from the bite can paralyze most of the muscles in a human. A human might die in less than five minutes.
The blue-ring octopus gets its name from bright blue circles that can appear all over its body and tentacles. These rings are nearly invisible when the animal is at rest. The rings glow when the octopus is alarmed. The glowing blue color warns others to stay away.
The blue-ring octopus likes to sneak up on its favorite food—crabs. The crabs are sometimes as big as the octopus. But the octopus is often able to "hug" the crab tightly with its eight tentacles. As soon as the octopus gets a good grip, it injects its toxin into the crab's body. Sometimes it will inject its toxin directly into the crab's eye. The toxin kills the crab quickly.
Like some other males in the animal world, the male blue-ring octopus dies shortly after mating. The female guards the eggs for about two months until they hatch. After that, she waits until another male comes along.