Enteroctopus dofleini

Giant Pacific octopuses, Enteroctopus dofleini, are found throughout the Pacific Ocean. They have been documented as far north as the Alaskan Aleutian Islands and as far south as the Baja California region of Mexico. This species ranges as far northeast as Japan. (Scheel, 2002)

Giant Pacific octopuses are generally found in tidal pools and up to depths of 110 m, although they can also reside in deeper waters of up to 1,500 m. They often live in dens or lairs, under boulders, and in rock crevices. Ideal habitat for this species includes a soft substrate of mud, sand or gravel that includes large boulders for creating dens. Giant Pacific octopuses are found in greater densities near dense kelp fields. Members of this species are ectothermic, and their metabolism is dependent upon water temperature. Optimal water temperatures for giant Pacific octopuses range between 7 and 9.5 degrees Celsius. (Scheel, et al., 2007; "North Pacific giant octopus (Enteroctopus dofleini)", 2010)

Giant Pacific octopuses are larger than any other species of octopus. Specimens have weighed as much as 272 kg and measured 9.6 m in radius. However, most reach an average weight of 60 kg with a dorsal mantle length of 50 to 60 cm. Giant Pacific octopuses 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. (Anderson, et al., 2002; Schwab, 1987; "North Pacific giant octopus (Enteroctopus dofleini)", 2010)

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. (Anderson, et al., 2002; Kubodera, 1991)

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 m 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 octopuses are polygynous. (Anderson, et al., 2002; High, 1976; Kubodera, 1991)

Giant Pacific octopuses breed throughout the year, though spawning peaks in winter. Males may breed with several females, but females mate only once in their lifetime. Over several days, females lay 20,000 to 100,000 rice-shaped eggs (avg. 50,000) in grape-like clusters of 200 to 300 eggs each. These clusters are hung from the ceiling of the den. Females remain with the eggs throughout the entire brooding period, guarding them from predators and using her syphon to aerate and clean the clusters. 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. (Anderson, et al., 2002; High, 1976; Kubodera, 1991; "North Pacific giant octopus (Enteroctopus dofleini)", 2010)

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. (High, 1976)

Giant Pacific octopuses on average live 4.5 to 5 years in the wild. A similar lifespan has been observed for members this species held in public aquariums. (High, 1976)

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. Members of this species are timid and rarely display aggressive behavior toward humans unless challenged. (Anderson and Mather, 2007; High, 1976; Scheel, et al., 2007)

Giant Pacific octopuses have a small home range of less than 5 square km.

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. (Anderson and Mather, 2007; Anderson, et al., 2002; Mather, 2008; Schwab, 1987; "North Pacific giant octopus (Enteroctopus dofleini)", 2010)

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. This collection of skeletal remains is known as a middens. Examination of middens indicates that the diet of giant Pacific octopuses is primarily composed 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. 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. (Anderson and Mather, 2007; Schwab, 1987)

Giant Pacific octopuses avoid predation by remaining in a protective den, camouflaging itself, or hiding among kelp. Although juveniles are eaten by a variety marine life, adult giant Pacific octopuses have few predators other than humans, which have hunted this species to use as food and as bait for Pacific halibut. Giant Pacific octopuses are known for their ability to release an ink cloud, although they rarely do so as a direct form of defense. Instead, they tend to fight off predators with their arms. Once released, they use their propulsion abilities to jet away. As giant Pacific octopuses escape, they then expel a cloud of ink as a screen, allowing them to seek safe refuge. (High, 1976)

Giant Pacific octopuses do not specialize on any one particular species of prey and are not the main source of food for any particular predator. They do, however, serve as host to some dicyemid mesozoans. Dicyemennea nouveli is a large, conical-shaped species that reaches up to 12,000 um in length. Dicyemennea nouveli inserts the pointed anterior end of its body into the folds of the renal appendages of giant Pacific octopuses. Other members of g. Dicyemennea are also found in shallow-water cephalopods. (Furuya, 2008)

Giant Pacific octopuses were commonly used as bait for Pacific halibut during the late 1950s and 1960s, though this is no longer a common practice. In some ares, this species is commercially fished and is eaten in some countries in the Pacific. (High, 1976; "North Pacific giant octopus (Enteroctopus dofleini)", 2010)

There are no known adverse effects of giant Pacific octopuses on humans.

Giant Pacific octopuses are not considered at risk by the IUCN Red List, CITES, or the US Federal List of Endangered Species. Although this spices is commercially fished in some areas, this does not appear to be greatly affecting population sizes. ("North Pacific giant octopus (Enteroctopus dofleini)", 2010)