Giant Pacific Octopus: Characteristics, Feeding and Reproduction

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Giant Pacific octopus (Enteroctopus dofleini)

The giant Pacific octopus (scientific name: Enteroctopus dofleini) is the largest octopus species. Also known as the North Pacific giant octopus, it belongs to the genus Enteroctopus and can reach a length of around five meters (16 feet) long and weigh over 250 kilograms (550 pounds). The length of the largest ones includes four-meter (13-foot) -long tentacles and a head the about the size of an American football. Typically though they weigh about 15 to 18 kilograms (33 to 40 pounds). Each of its eight arms are about 2.2 meters long (five feet) long and have 2000 suckers.

Giant Pacific octopuses have dorsal mantle that typically measures 50 to 60 centimeters (1.6 to 1.8 feet) in length. They are usually reddish in color but are able to change color and texture when threatened or for camouflage. The dorsal mantle is shaped like a sack and contains the brain, reproductive organs, digestive organs, and eyes. Giant Pacific octopuses have two eyes, one on each side of their head, which provide extremely acute vision. Giant Pacific octopuses also have four pairs of arms that extend from the mantle. Each pair is covered with up to 280 suckers, which contain thousands of chemical receptors.

Giant Pacific octopuses were commonly used as bait for Pacific halibut during the late 1950s and 1960s, but this is no longer the case. They are as commonly eaten and commercially fished as some other octopus species in Asia. Although their numbers are not they are not considered at risk by the International Union for Conservation of Nature (IUCN) Red List, the International Trade in Endangered Species (CITES) or the US Federal List of Endangered Species.

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal

Giant Pacific Octopus Habitat and Where They Are Found

range of the Giant Pacific octopus

The giant Pacific octopus is found primarily in the the coastal North Pacific, from Baja California in Mexico to Alaska and is particularly associated with the Pacific Northwest (Oregon and Washington) in the U.S. and British Columbia in Canada. It is also found in coastal waters off Russia, Eastern China, Japan, and the Korean Peninsula. [Source: Wikipedia]

The giant Pacific octopus can be found from intertidal zones at the ocean surface down to depths of 2,000 meters (6,600 feet). Members of this species are ectothermic (cold blooded, with their metabolism dependent upon water temperature) and do best in cold, oxygen-rich water. Optimal water temperatures for giant Pacific octopuses range between 7̊ and 9.5̊ Celsius (45̊ and 49F. There average lifespan in the wild is 4.5 to 5 years. Similar lifespan numbers have has been observed by individuals kept in public aquariums.

Giant Pacific octopuses are often found in tidal pools. They often live in dens or lairs, under boulders, and in rock crevices as well as ocean bottom areas of soft mud, sand or gravel that includes large boulders for creating dens. Giant Pacific octopuses are found in their greatest concentrations in dense kelp forests. Colleen Hartis, Animal Diversity Web (ADW)]

Giant Pacific Octopus Size and the Seven-Arm Octopus

The largest verified giant Pacific octopus weighed 71 kilogram (157-pounds) when weighed live. Adults usually weigh around 15 kilograms (33 pounds), with an arm span up to 4.3 meters (14 feet). Larger individuals weigh around 50 kilograms (110 pounds) and have a radial span of six meters (20 feet). American zoologist G. H. Parker found that the largest suckers on a giant Pacific octopus are about 6.4 centimeters (2.5 inche) and can lift up 16 kilograms (35 pounds) each. The closest rival for the largest title is the seven-arm octopus (Haliphron atlanticus). One specimen of this species weighed 61 kilogram (134-pound) and an incomplete carcass was estimated to have weighed 75 kilograms (165 pounds) and measured 3.5 meters (11 feet). [Source: Wikipedia]

Giant Pacific octopus

There have been a number of questionable size records and unverified claims, including a report of one up that weighed 272 kilograms (600 pounds) and had a nine meter (30-foot) arm span. The Guinness Book of World Records lists the biggest as 136 kilograms (300 pounds) with an arm span of 9.8 meters (32 feet). A UN catalog of octopuses says the Giant Pacific octopus can reach 180 kilograms (400 pounds) with an arm length of 3 meters (9.8 feet).

The seven-arm octopus (Haliphron atlanticus) is very rare. It gets its name because the males’ hectocotylus (a specially modified arm used in egg fertilization) is coiled in a sac beneath it right eye and not visible so it looks like the octopus has seven rather than eight arms. The species was thought to live only in the Atlantic Ocean. Specimens have been caught throughout the Atlantic, including off the Azores and near South Georgia Island. In 2002, a giant octopus was caught by fishermen trawling at a depth of 920 meters off the eastern Chatham Rise, New Zealand. It had a mantle length of 69 centimeters (2.3 feet), a total length of 2.9 meters (9.5 feet), and weighed 61 kilograms (134.5 pounds) but was incomplete.

Giant Pacific Octopus Behavior, Senses and Intelligence

Giant Pacific octopuses are solitary and often remain inside the same den for weeks at a time, leaving only to capture food, mate, or escape predation. They are timid and rarely display aggressive behavior toward humans unless provoked Giant Pacific octopuses have a small home range of less than 5 square km. [Source: Colleen Hartis, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Each pair of arms of giant Pacific octopuses has up to 280 suckers, which have thousands of chemical receptors. These provide an acute sense of touch and taste, which this species use to help detect prey. Typically calm animals, giant Pacific octopuses are unusually adept at navigating by using landmarks in the wild and at adapting objects as tools. They are the only invertebrate known to use their well-developed vision to learn through observation. /=\

Giant Pacific octopuses are considered extremely intelligent, partially do to their larger-than-average brain-to-body weight ratio. Individuals in captivity are known for having having unique temperaments and personalities, ranging from playful to destructive. Their high level of intelligence and desire to interact with human caretakers have earned captive members of this spices a reputation as notorious escape artists. Giant Pacific octopuses in aquariums have demonstrated the ability to recognize humans and socialize with them by shooting jets of water and changing their body texture. These octopus have about 300 million neurons in their brain and nervous system. They have open tank valves, disassembled expensive equipment, and ruined lab and and aquarium equipment. [Source: Wikipedia]

Giant Pacific Octopus Mating and Reproduction

Giant Pacific octopus with eggs

Giant Pacific octopuses are 1) oviparous (young are hatched from eggs); 2) engage in internal reproduction in which sperm from the male fertilizes the egg within the female; and 3) employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. [Source: Colleen Hartis, Animal Diversity Web (ADW)]

Giant Pacific octopuses breed year-round. Males may breed with several females once reaching maturity, but females mate only once in their lifetime. The number of offspring ranges from 20,000 to 100,000, with the average number being 50,000. Both males and females reach sexual maturity at ages 3 to 5 years.

According to Animal Diversity Web: Male reproductive organs of great Pacific octopuses are enclosed inside the mantle cavity within a genital bag. Spermatozoa are encapsulated in a spindle-shaped spermatophoric sac. Males utilizes a hectocotylized arm, a specialized tentacle used for the transfer of sperm, to insert the two spermatophores (each 1 meters in length) into an oviduct located in the mantle of the female. The balloon part of the spermatophore remains inside the oviduct while the remainder of the sac hangs from the female. Eventually, the sac bursts and releases millions of spermatozoa. The entire mating process takes 2 to 3 hours.

Giant Pacific Octopus Brooding and Development

According to Animal Diversity Web: Female giant Pacific octopuses remain with their eggs throughout the entire brooding period, guarding them from predators and using their syphon to aerate and clean the clusters. Females do not leave the den during this period, not even to eat. Females die during the brooding period or shortly thereafter, and males die within three months of breeding. Therefore, there is no post-hatching parental investment evident in giant Pacific octopuses. [Source: Colleen Hartis, Animal Diversity Web (ADW)]

The rice-shaped eggs are grouped in grape-like clusters of 200 to 300 eggs each. These clusters are hung from the ceiling of the den. Hatching can take anywhere from 150 days to almost 1 year depending on water temperature. Cooler temperatures delay the development of the embryo and therefore lengthen incubation time.

Giant Pacific octopus young

The lifespan of giant Pacific octopuses is characterized by a fast growth period that continues throughout its entire life of 4 to 5 years. Larvae hatch from a cluster of eggs and are on average 9.5 to 10.1 mm in length. The larvae, with limited swimming ability, move to the surface to begin a planktonic existence that lasts 1 to 3 months. At the end of the planktonic stage, juveniles descend to the benthos where they undergo rapid growth. Giant Pacific octopuses continue to grow until they reproduce. Within 3 months of breeding, males normally undergo a period of senescence and die. Symptoms of senescence in this species include reduced food intake, retraction of skin around the eyes, aimless movement (wandering) and lesions that do not heal. Females that survive brooding undergo a similar period of senescence and die within weeks of the eggs hatching.

Giant Pacific Octopus Feeding and Predators

Giant Pacific octopuses prey upon crabs, scallops, shrimp, abalone, squid, snails, clams, cockles, lobsters, fish, and other octopuses. Giant Pacific octopuses are considered generalist foragers. They return to their den in order to consume their prey, and they deposit the prey's remains at the entrance of their den in what are known as a middens. Examination of middens provides evidence of them eating the prey named above and indicates their diet consists primarily of clams, crabs, fish, and squid.

Giant Pacific octopuses are visual hunters that utilize a variety of hunting strategies including stalking, chasing, and camouflaging themselves in order to ambush prey. Food is often grabbed with with their suckers and then bitten using its tough beak of chitin. One in captivity was once observed snagging a 1.2-meter spiny dogfish. Consumed carcasses of this same shark species have been found in wild giant Pacific octopus middens. In 2012, amateur photographer Ginger Morneau photographed a wild giant Pacific octopus attacking and drowning a seagull. [Source: Wikipedia +]

According to Animal Diversity Web: They possesses a well-developed sense of vision, allowing them to coordinate the use of all eight arms to attack their victim. Members of this species also use different methods to prepare meals for consumption. One method includes pulling the protective shell apart in order to reach the meat contained inside. Another method involves crushing prey with their strong beak located in the center of its appendages. The most common method of obtaining food, however, involves drilling a hole in the prey's shell, in which an octopus injects its toxic saliva. [Source: Colleen Hartis, Animal Diversity Web (ADW)]

Various scavengers and other creatures try to eat octopus eggs, even when the female is protecting them. Paralarvae are preyed upon by many other zooplankton and filter feeders. Adults are an important food source for harbor seals, sea otters, and sperm whales as well as for Pacific sleeper sharks. Giant Pacific octopuses avoid predation by remaining in their dens, camouflaging themselves and hiding among kelp. Giant Pacific octopuses have the ability to release ink clouds but they seem more inclined to fight off predators with their arms or make a quick escape using jet propulsion.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated April 2023

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