A red octopus's normal color is red or reddish brown, but like other octopuses it can change quickly—in a fraction of a second—to yellow, brown, white, red or a variety of mottled colors. To defend themselves or for social signaling (for example, courting), octopuses change to color patterns that contrast with their surroundings. To camouflage themselves, octopuses change to color patterns that blend with their surroundings. They can also alter their skin texture to match sand or the surface of smooth or rough rocks.
An octopus usually forages at night, collecting several specimens before retreating to its den, where it eats at leisure. The octopus kills its prey (crabs are a favorite food) with venom secreted from its salivary glands, then cracks the shell with its sharp beak. If the prey is a snail, the octopus drills a hole in the snail's shell with its radula and injects a chemical that dissolves the snail's flesh from its shell. An octopus deposits empty shells outside its den in a pile–commonly called an "octopus's garden."
While tidepooling, you might see a red octopus in the intertidal zone, but it's best not to touch it. Red octopuses have sharp beaks and are inclined to bite and then spit venom on the wound. Healing from an octopus bite might take three weeks.
Octopus eyes are similar to vertebrate eyes, with lenses, retinas and pupils. Although they have excellent eyesight, they use touch and smell to find food—thousands of chemical receptors and millions of texture receptors line the rims of their suckers. An octopus scours the sandy seafloor to flush out small prey, or crawls in and out of rocky areas to hunt crabs and shrimp.
Red octopuses live about two years. They begin life as larvae in the intertidal and shallow subtidal zones, spending a short time drifting as plankton. They change into adult form before settling as juveniles on kelp holdfasts. Later, they migrate farther offshore, where they settle on sandy mud sea bottoms. According to researchers who explore the Monterey Canyon with an ROV (remotely operated vehicle), the red octopus is the most common animal found along the continental shelf—at depths of 600 feet (183 m)! Red octopuses mate in late winter and early spring before moving to the intertidal area, where they spawn. Females protect and groom eggs until the larvae hatch six to eight weeks later. The females then die; the males die after mating.
Octopuses are highly developed marine molluscs. They have three hearts—one pumps blood through the body and the other two pump blood through the gills. Researchers consider octopuses to be the most intelligent invertebrates—maybe as intelligent as a house cat.