Giant Pacific octopuses are the largest of all octopus species, usually stretching to around 4m long.
They are highly intelligent masters of camouflage and, while they prefer small fish and shelled animals, they have been known to eat sharks.
What is a giant Pacific octopus?
Giant Pacific octopuses (Enteroctopus dofleini) – sometimes shortened to GPOs – are the largest of all octopus species. These leviathans grow to several metres long. The biggest specimen in the world is said to have grown almost 10m long – that’s around the length of a school bus. They’re very clever, excel at camouflage and make excellent mothers.
How big is a giant Pacific octopus?
When we say giant, we really mean giant. These titans are the world's biggest octopus. They typically grow to lengths of 2–4m and weigh in at over 20kg. The largest specimen ever found reportedly measured 9.75m long and weighed 272kg.
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What do they look like?
These large, reddish-brown creatures have soft boneless bodies with eight arms, which can each operate independently to the other. They have thousands of suckers along their arms, filled with chemical receptors that enable them to taste everything they touch.
Although huge, they’re good at blending in and can change the colour and textures of their skin in a split second to camouflage seamlessly with their surroundings, thanks to special cells called chromatophores.
What do they eat?
Giant Pacific octopuses have a varied diet and eat a little bit of everything, from fish, shrimp, clams and crabs to lobsters, scallops, and even other octopuses. When the opportunity arises, they’ve also been known to eat small sharks.
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How do they hunt?
To get hold of this seafood banquet, giant Pacific octopuses use one of their key talents: stealth. They hunt at night, using their camouflage to help them creep up on unsuspecting prey. Once they’ve snuck up close enough, they can use jet propulsion to speed towards them before the victim has a chance to get away. Then, they grab them. The strong suckers along their arms make it almost impossible to escape.
When they bite into their hapless prey, their saliva contains a venom that will paralyse it. They often bring their meal back to their den to scoff it down, like picking up takeout. Their beaks and radula (which is like a tongue) are strong enough to tear through the tough exoskeleton of shelled animals such as crabs and lobster to get to the delicious flesh inside.
Once they’ve finished their meal, they toss the shells and bones away. These discarded items into an accumulate little pile, called a midden. Scuba divers know that if they see a heap of discarded shells and bones, there might be an octopus living nearby.
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Where do they live?
As their name suggested, these gigantic cephalopods live in the Pacific Ocean. They can be found at a range of depths – from the shallows all the way down to around 1,500m deep – from Japan and Korea to Canada, the USA and Mexico.
How do they reproduce?
Octopus sex is weird to say the least. The male has a modified arm, called the hectocotylus, that it uses to deliver a sperm packet to the female. She then stores the sperm until she decides that she’s ready to reproduce. She will do so only once towards the end of her life – laying tens of thousands, or even hundreds of thousands of eggs in a long string and tending to them devotedly.
It takes around six months before the eggs hatch and the mother octopus won’t eat during this time. Instead, she is fully dedicated to protecting her young from potential predators. This is her last act – the female dies soon after her eggs hatch.
Are they dangerous to humans?
Some say the terrifying mythical beast known as the Kraken was inspired by an enormous octopus or giant squid. But giant Pacific octopuses generally aren’t dangerous to humans.
Like all octopuses, GPOs are venomous. When they bite into prey, they use their sharp beak to inject a toxin that incapacitates their victim. Although this sounds like these enormous animals would be a huge threat to humans, they are much less dangerous than the tiny blue ringed octopus, which is the most venomous species of octopus (and deceptively cute).
Giant Pacific octopuses aren’t usually aggressive towards humans – unless they feel provoked – and their venom is not usually fatal to people if treated promptly. That said, these are wild animals so it’s always sensible to give them plenty of space and, if you are unlucky enough to get bitten, seek medical help immediately.
How intelligent are they?
Like other cephalopods, these are incredibly clever critters. This is, perhaps, not surprising when you consider that they have nine brains – one centralised brain plus one smaller brain in each of their eight arms. With one of these ‘mini brains’ controlling each limb, each of their arms can undertake a distinct task at the same time. Talk about multi-tasking!
Giant Pacific octopuses are believed to be the most intelligent of all invertebrates. They can open jars, solve puzzles and mazes, squeeze through tiny spaces, and recognise individual humans. They’ve even figured out how to pinch a fisherman’s catch to eat themselves.
When they’re kept in zoos and aquaria (which is common for this species), keepers use enrichment exercises like puzzle boxes to keep them entertained.
Are they under threat?
The Giant Pacific octopus is currently categorised as being of Least Concern by the IUCN Red List, although it was last assessed in 2014.
Like other marine creatures, octopus – including the giant Pacific – are threatened by overfishing, pollution and habitat loss.
They are often caught as bycatch by fisheries that use pots to catch species like crab or cod. The inquisitive octopuses spot the animals caught in the pots and realise they could snaffle an easy meal, but they can then get caught in the fishing gear themselves. Scientists believe that, if released quickly, the octopuses have a relatively high chance of survival.
Giant Pacific octopus - special features
- Mantle
- Nine brains
- Beak
- Salivary gland to produce venom
- Siphon (funnel)
- Three hearts
- Special colour-changing cells in its skin
- Eight arms
- Suckers
Giant Pacific octopus - facts at a glance
Scientific name: Enteroctopus dofleini
Nicknames: North Pacific giant octopus, GPO
Length: Typically, just over 4m across but bigger specimens have been found
Average lifespan: Between three and five years in the wild
Weight: Varies but can be around 50kg
Depth: Both deep and shallow waters but commonly found around 5m
Top image: Giant Pacific octopus. Credit: Getty
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