They are not known to maintain a large territory. An individual will often frequent the same den over a long period of time. Once thought to be nocturnal, research now suggests that they are simply frequent nappers. They stay in their dens for regular rest times then go out to hunt for food. They are solitary animals, interacting with their own kind only to mate. Their bodies are well suited to their lifestyle. They prefer to crawl along on the ocean floor, but when they need to move quickly, they suck water into their bodies and shoot it out through a special tube, thrusting themselves thought the water. When threatened, they shoot ink at their enemies. This ink can take on the shape of a decoy octopus as it spread out, confusing other animals. It also affects the enemy's sense of smell, enabling them to get away safely. Octopuses are considered the most intelligent of all the invertebrates. Their major predators are seals, sea lions, and large fish such as lingcod and halibut. They are able to regenerate limbs that are lost to predators.