With its writhing tentacles and eerie ability to figure things out, the octopus is one of the strangest animals in the sea, or on Earth, for that matter. Its alien appearance and sliminess unnerve some people, offering plenty of material for nightmares and legends. Octopus stories abound around the globe, including seafaring yarns about huge, blood-thirsty “devilfish” tearing ships to bits. While these stories are usually debunked, the uncanny abilities and physique of the remarkable giant octopus make these tales hard to let go.
Large, but Short-Lived MolluskThe largest of at least 90 subspecies of octopus, the giant octopus can grow to 300 pounds and have a 30-foot arm span. However, mature males average only about 50 pounds and females, about 33 pounds. Their arm spans typically are about eight feet. Despite its fearsome appearance, the giant octopus—while quite resourceful—is very shy and poses little danger to divers, fishermen, or swimmers. These mollusks are distant relatives of garden snails and slugs, and closer relatives of squids and cuttlefish. The giant octopus can be found in the coastal waters of northern California through the Gulf of Alaska, and around the Pacific Rim to Japan and Korea. They live in waters just beyond the low-tide mark to depths of up to 1,500 feet along the continental shelf. They usually live about three to five years.
A giant octopus spends most of its day lurking in a rocky crevice, emerging at night to forage for prey. When it ventures out, it typically crawls along the sea floor, often with surprising speed. Above the floor, it propels itself by a water jet thrust out through its gill chamber.
A giant octopus eats almost anything it can catch, with crabs at the top of its list of favorites. It also catches fish and other octopuses. It hunts mainly by sight. The octopus surges forward and envelops prey with its strong tentacles. Its suckers have touch sensors and chemical receptors that it uses to check out its catch, allowing it to reject anything that feels or tastes wrong. Sometimes the octopus paralyses its victim with venom from its salivary glands, but usually it just rips prey apart with its powerful suckers. The octopus kills crabs with a shell-crushing bite from the parrot-like beak concealed at the center of its tentacles. It then scoops out the flesh and discards any shell outside its lair.
Male giant octopuses mature sexually before females. During mating, the male uses a specialized tentacle to insert a sperm packet into the female. The male dies soon after mating. The female produces up to 100,000 eggs, which she attaches to the ceiling of her den. She guards her eggs for six months, never eating or even leaving her den. She oxygenates her eggs by shooting water over them from her gills. Exhausted by breeding and starved by the vigil over her eggs, the female dies almost as soon as the eggs hatch. Each egg hatches into a tiny octopus about one-quarter of an inch long. Baby octopuses swim to the surface to live as plankton—tiny plants and animals that drift in the ocean—until settling on the seabed when about one-half ounce in weight where it grows at an amazing rate—reaching two to three pounds in one year and then continuing to gain about two percent of body weight per day! Few hatchlings, however, ever reach maturity before becoming food for fish, moray eels, sea lions, or other octopuses.
Intelligent Invertebrate?The giant octopus has the largest central nervous system—mostly brain—of all invertebrates, rivaling that of many vertebrates, including birds and fish. It can do some really amazing things. But is it intelligent? Herein lies much debate-fodder for scientists. The fact that octopuses survive despite being soft, tasty creatures suggests to some that they are resourceful and intelligent. They also appear quite capable of solving simple puzzles, learning, and remembering. Scientists have trained captive specimens to negotiate their way through simple mazes and distinguish squares from crosses. They have been taught to unscrew lids from food jars and have been observed learning by watching the behavior of other octopuses.
But other scientists aren’t so sure that big brains mean greater intelligence. They suggest that a big brain may be necessary to operate such a complex animal with sophisticated eyes, eight versatile tentacles, ability to change color, sensitive suckers.
Dazzling Array of Defensive and Offensive Weapons
Suckers. The octopus uses its suckers to rip prey apart and anchor itself to a rocky surface. Sensors around each sucker allow the animal to reject anything that tastes or feels wrong.
Tentacles. The octopus has eight strong arms capable of pushing, pulling, and grasping prey tightly.
Beak. The giant octopus uses its powerful beak to crush crab shells.
Venom. Venom in its salivary glands contains a chemical that helps the octopus disable prey and break down its muscle tissue.
Ink. The octopus can disorient a pursuer by squirting a burst of purplish-black ink.
Appendage Regeneration. Should the animal lose a tentacle to a predator, it can grow a new limb.
Camouflage. The octopus can change the color and texture of its skin cells in less than one second to blend in with its surroundings. These cells in its skin called chromatophores are under muscular control, allowing different pigments to come into view as the cell walls are stretched or squeezed. One expert suggests that “Chameleons are just dead-boring compared to octopuses.”
A giant octopus can live out of water for some time as long as it stays cool and damp. It may leave the water to search for food on land. To snatch quick snacks, octopuses have been known to climb aboard fishing boats and open fish holds full of crabs or to break out of aquariums to prow around rooms for tasty inhabitants in other tanks. They generally have up to one-half hour out of water before they die from lack of oxygen.
Octopus blood is a poor carrier of oxygen. To compensate, these animals have three hearts and permanently high blood pressure. As a result of these physiological inefficiencies, the octopus has poor stamina and an inability to struggle offensively or defensively for very long.
By day giant octopuses retreat to dens under rocks or in holes. At the entrance, one typically observes an “octopus’s garden” composed of a collection of bones, spines, and shells from past meals.
An octopus can squeeze through an opening no bigger than one of its eyes.
An octopus’s brain continues to grow throughout the life of the animal and consists of over 170 million nerve cells, three-quarters of which are involved in vision.
Conservation StatusGiant octopuses are important members of the oceanic web of life. As hatchlings they enter the low end of the food chain—the diverse plankton soup—that feeds myriads of animals. As they grow to maturity, they climb to almost the top of the ocean’s food chain to become a formidable predator.
The giant octopus is currently not considered endangered, and some intrepid enthusiasts keep them as pets, although this requires a major commitment. The giant octopus is vulnerable to pollution, but unlike its edible relative, the common octopus, it is not in direct danger from humans even though there is a small commercial fishery for it from Alaska to Northern California, mainly as a bait for halibut fisheries. In Oregon, many octopus are taken as incidental catch in the Dungeness crab pot fishery and the groundfish trawl fishery. Octopus overfishing, however, appears to have occurred in Japan and in sport dive fisheries in the straits between Vancouver Island and mainland British Columbia.
Enriching an Octopus’s Life—the Zoo ExperienceThe National Zoo currently has a female giant octopus in residence at its Invertebrate Exhibit
. It is a very popular animal at the Zoo mainly because, unlike many Zoo animals, the giant octopus is familiar to most visitors through stories. Also, adding to its appeal, the animal is large and gregarious, never missing an opportunity to react and interact. Few can resist the opportunity to look the octopus in the eye and have it stare back. One keeper calls the giant octopus “the Invertebrate Exhibit’s giant panda.” This popular mollusk is fed a diet of shrimp, fish, and crab.
To provide this fascinating animal opportunities for exploration and interaction similar to those observed in the wild, the Zoo has implemented an Octopus Enrichment Program
. Under the watch of a trained observer, a new object—such as a jar, tube, or rubber dog toy—is introduced periodically to the octopus. With each introduction the animal's behavior is recorded to identify the level of interaction with the object. In addition, the tank contains shelves, archways, and doors. New objects and complexities are planned for the future to give this mollusk with a sophisticated brain a new and broader array of challenges.
Adopt a Giant OctopusWhy not consider adopting this wild and wonderful giant from the deep for yourself or for a special someone? An Adopt a Giant Octopus package would make an especially wonderful educational gift for a child. Your adopt contribution will support exhibit improvement, medical care, and food not only for the giant octopus but also for the more than 2,400 other animals that reside at the National Zoo and its Conservation and Research Center at Front Royal, Virginia.