Deep Intelligence - the Giant Pacific Octopus

A Giant Pacific Octopus glides along a rocky underwater wall in central Puget Sound.

A Giant Pacific Octopus nestles in a small cleft at Sunrise Wall near Tacoma, Washington.

A Giant Pacific Octopus out in the open at Renate's Reef in Barkley Sound, British Columbia.

A diver peers at a Giant Pacific Octopus hidden inside a wall crack in Barkley Sound, British Columbia.

A Giant Pacific Octopus glares out at the camera lens from its hiding place in Nootka Sound, British Columbia.

A Giant Pacific Octopus comfortably resting inside its den in Nootka Sound, British Columbia.

A diver shares a morsel with a Giant Pacific Octopus, its tentacle snaking out of the den to investigate the offering.

From out of the corner of my eye, I watched as my dive buddy, Jerome Ryan, glided slowly downward into the deep emerald-green gloom that is Puget Sound, sun beams dancing down from the surface glistening on the back of his tanks. Within seconds the bottom began to take shape and the bright pink encrusting hydrocorals enshrouding the rock wall burst into my view. Together, we turned and let the subtle current slowly sweep us across the rocky face, our eyes darting here and there seeking the wonders of our cold underwater world. Within moments a subtle movement attracted our attention and we were drawn toward what at first appeared to be part of the rock structure. Instead, it proved to be one of our favorite creatures – a Giant Pacific Octopus – completely out in the open and doing some "exploring" of its own. Quietly we approached, Jerome holding out a hand with a finger extended. Slowly, almost imperceptibly, a long arm began to creep along the rocky ledge toward the proffered hand. Ultimately the tip of the arm touched Jerome's dry glove and it began to slither around his fingers and palm, as if savoring this strange new sensation. The occasion was only disturbed by the occasional flash from my camera strobe, recording the scene. It was a magical moment…..the photos I took will never do it justice……

The Giant Pacific Octopus is a cephalopod mollusc, a class that contains all other octopuses, squid and cuttlefish. It is regarded as the largest species of octopus in the world. Until recently it was known as Octopus dofleini, but in 1998 was re-classified as Enteroctopus dofleini, part of a genus that includes all other giant octopus species. Rumors abound in the Pacific Northwest regarding the size to which E. dofleini is capable of growing, including one supposedly found dead years ago in the Ballard Locks in Seattle that is said to have exceeded 30 feet in local mythology. Tall tales aside, the most impressive "official" record that I have been able to locate is one from the Canadian Department of Fisheries and Oceans web site, indicating that the largest Giant Pacific Octopus on record weighed 272 kg (599.6 pounds!) with a total arm spread of 9.6 meters (31.5 feet!). Others have reportedly been found within the 300 to 400 pound range. Many biologists, however, dispute these "records", and in reality finding one that exceeds 100 pounds is extremely unusual. Generally, it is agreed that E. dofleini can reach a size of over 150 pounds, although a typical adult will be in the 60 to 80 pound range. Still, the size of the Giant Pacific Octopus is apparently limited only by the quality and quantity of its food……literally, if it eats well, it'll GROW!

Like all octopuses, E. dofleini has eight arms attached to the head/mantle area centered around a mouth. They have no bones – the only hard part of their body being a beak used to bite and kill prey. Each arm has rows of suckers along the full length to the tip. The arms are incredibly sensitive and have many nerves within them as well as in the suckers themselves. Octopuses can actually taste with their suckers and use them as one of their primary means of gathering information along with their excellent eyesight. E. dofleini has two rows of suckers per arm and can have as many as 1,600 of them. The mantle itself resembles a large bag that moves in and out as the octopus breathes. It contains the stomach and all of the other organs, including 3 hearts. Two of the hearts pump blood through the gills while the third pumps it through the body itself. When octopuses breathe in, water flows over the gills and fills the mantle, when they breathe out the water is forced from the mantle through a tube called a siphon. E. dofleini can force water through this siphon in such a manner that it can jet propel itself away from predators (or a too-curious diver) and have been known to travel large distances in this manner. Octopuses are known to be the most intelligent of the invertebrates and documentation exists that clearly shows evidence of curiosity, memory, planning, and even personality. Their skills include problem solving, stealth and mimicry and they have been known to open jars, make use of tools, and even to play. The Giants are also masters of camouflage, having specialized cells in their skin known as chromatophores that are under direct neural control. This allows them to change color in a matter of seconds based on their surroundings or situation, and also enables them to make patterns on their skin based on a series of rapid color changes. Further, they can raise or lower papillae on their skin, literally changing their texture in an instant. Combined, these abilities allow E. dofleini to rapidly change color, shape, position and texture from one moment to the next. When a diver witnesses such a spectacle it is one of the most beautiful sights in nature, but realistically speaking these capabilities are what make the Giant Pacific Octopus one of the most effective predators in the sea.

When it comes to food, E. dofleini and humans seem to share many of the same seafood preferences. In fact, when recently dining at a locally famous seafood restaurant near Seattle I was struck by how much the menu resembled a list of octopus favorites! In Puget Sound, the delectable Dungeness crab heads the list of preferred food items, but all types of shrimp, clams, crustaceans, fish and other molluscs are also on the menu. Octopuses are among the most mobile of the oceans' predators and will travel extensively in search of their food. However, they will normally return to their den after their hunting expeditions, bringing their prey with them for "in-house dining". One of the most certain signs of current or recent den occupancy is a large accumulation of crab shells and other shellfish debris near the mouth of the den. A den located in an area of particular food abundance can often have a midden of discarded and broken shells several feet high. Normally hunting at night, E. dofleini requires a heavy abundance of speed, stealth and skill to catch its favorite meal - Dungeness Crab are master sprinters and are capable of awe-inspiring bursts of speed when fleeing a hungry octopus (or diver!). Typically, the hunting tactics of E. dofleini involve a slow approach by stealth with each of the independent arms surrounding the unsuspecting victim, coupled with a sudden burst of speed in which the prey is enshrouded by the arm web and held in place with the suckers. The octopus' beak is then used to kill the prey and tear it into pieces for feeding.

Dwelling on the continental shelf of Western North America as well as Northern Japan and the Russian far-east, the range of E. dofleini extends in the United States from Southern California up the Pacific coast to the tip of the Aleutian Islands in Alaska. E. dofleini can literally be found everywhere within Puget Sound but have a decided preference for areas containing abundant food sources as well as the best denning opportunities. Dens are vital to these giants at virtually all stages of their development, so sites with abundant natural or artificial dens are extremely attractive to them. Most dens are found in naturally occurring holes, cracks or crevices within rocks or walls, although often E. dofleini will dig a suitable den in sand or under a log or rock if a ready-made den isn't immediately available. Man-made objects are also popular as dens and octopuses can often be located within the nooks and crannies of wrecks, abandoned sewer pipes, and any other type of suitable debris. Small octopuses can also be found denning within bottles, jars or pipes on the bottom. Dens are usually only temporarily occupied, an octopus generally remaining in an area only so long as the food supply lasts. It will move on to greener pastures once hunting becomes difficult or foraging expeditions more far ranging. E. dofleini does not appear to be territorial, although smaller octopuses will generally retreat from a larger individual should one be encountered. The Giant Pacific Octopus is an asocial animal – they do not deliberately avoid each other, but they also do not seek each other's company except when breeding is on the agenda. In areas where dens are scarce, competition for them may be intense and divers may find several octopuses near each other simply because of the close proximity of good den opportunities.

Generally, males reach sexual maturity at approximately 26 pounds in weight and females at approximately 44 pounds. This will normally occur between 2 and 3 years of age. When a female is ready to mate it is believed she releases chemicals into the water column that in turn attract males to her. In the Pacific Northwest mating normally occurs in the Fall and pairs can often be sighted during that time. The third right arm of the male is modified with a sexual organ (ligula) that may develop to be fully 1/5 the length of the entire arm, (small wonder humans often find themselves envious of the Giant Octopus!). The ligula is used by the male to insert two large spermatophores (up to 1 meter in length) into the mantle of the female, who then stores the sperm in them for later use. Males may mate with multiple partners, but females appear to be selective – preferring larger males to smaller ones. Females will seek out a secure, rocky den and lay their eggs approximately 2 months after mating. Between 20,000 and 80,000 eggs are laid over a period of several days and are attached to the ceiling and walls of the den itself. The female will then remain in the den with her eggs, constantly cleaning, tending and aerating them with her siphon. She will not leave the den; even to seek out food for herself, despite the fact that incubation of the eggs can take as long as between 5 and 7 months. When the time arrives, she will induce the eggs to hatch by manipulating them with her arms and suckers. Her last act will be to blow the larvae out of the den with her siphon. E. dofleini females die immediately after the hatching of their eggs, having sacrificed all of their strength and energy in caring for their brood. Males are also not long-lived, and may survive only several months beyond mating. Generally, females live approximately 3.5 years with males around 4 years. After hatching, larval octopuses are approximately the size of a grain of rice and swim upward to become part of the heavy surface layer of plankton. There they will remain until they have reached a size at which they are capable of surviving on the bottom of the ocean – usually after about 6 weeks.

As was mentioned briefly above, male octopuses generally reach the end of their lives approximately a few months or so after the females, although in a far different manner. Males in the last period of their lives tend to head out and explore their surroundings, or as Dr. Roland Anderson of the Seattle Aquarium puts it, they "go on walk-about"! They often can be found during the Summer months out in the open during daylight hours, sometimes in small groups of similarly aged individuals, and will commonly approach divers as if satisfying their curiosity. The number of diver sightings of large octopuses markedly increases during this time period as both species (octopuses and humans) are increasingly "out and about" exploring and discovering their world.

The author would like to extend special thanks to Seattle Aquarium Marine Biologists Roland C. Anderson, PhD., and Jeff Christiansen for their assistance and input regarding the content of this article.

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