Average adult size: Adults can grow to be 18 inches across.

Natural history: Octopuses have 8 arms with hundreds of cup-like suckers in two rows. The octopus usually hides from predators by blending perfectly with its surroundings. Masters of camouflage, they can change color and texture in the blink of an eye. Octopuses have a secret weapon: They can confuse their enemies by ejecting a cloud of ink. This smoke screen allows the octopus to make a disappearing act. Its main enemies are the moray eel and large fishes. In an emergency the octopus can also escape a predator by jet-propulsion, it can squirt a blast of water out of its siphon to escape.

Octopuses have well-developed eyes, similar to our own. They are sensitive to low light for hunting at dawn and dusk. Octopuses are the most intelligent of all the invertebrates. With a well-developed brain, octopuses can learn tricks as easily as a dog. Octopuses are active at dawn and dusk, leaving their den to hunt. They blend into their surroundings and grab passing prey with their long arms. Octopuses bite their victims with a "beak," then inject a venom that effects the prey's nervous system. Octopuses feed on crabs, snails, clams, small fishes and shrimps. Tidy eaters, they leave neat piles of shells outside their den, called a midden. Most medium-sized octopuses live only one-and-a-half to two years. Octopus eggs hatch in about four to six weeks. Most females stop eating while brooding the eggs and die after the eggs hatch.

Range: From Panama north to southern California.