Though octopuses and squid are both formidable fighters in the wild, they aren't typically dangerous to people. That doesn't mean they're always harmless. Some species are particularly well equipped for defending themselves against larger creatures, and they're strong enough to kill a human if they felt threatened.
Attack and Defense
Octopuses and squids are very similar biologically, and they use many of the same mechanisms for attack and defense. For example, both have hard, sharp beaks piercing the flesh and shells of their enemies and prey, scraping and pulling apart their meals. Both have arms lined with powerful suckers for grabbing prey. Octopuses can bite their prey and inject it with poison. Squids can squirt dark ink that clouds the water to confuse predators while the squids escape.
Fortunately for land-dwellers, octopus and squid defense mechanisms aren't a serious threat to humans. Most of their poisons are strong enough to subdue their typical prey, but not to harm humans. Squid ink is sometimes used as an ingredient in foods such as black pasta. Some octopuses are more dangerous to humans than others. Most notable is the blue-ringed octopus, which lives near Australia. This octopus's bite can kill a human because the venom causes paralysis that stops breathing.
The Humboldt squid has a particularly notable reputation as dangerous to humans, and it's sometimes advertised as a vicious man-killer who swarms and devours humans in large groups. This squid, who can grow to between 3 and 6 feet long, does travel in groups of up to several hundred, but the reality and the myth separate there. Unlike predators such as sharks, this squid lacks intent to harm humans, although it shows curiosity about us and could do some harm with his beak. This squid is used to eating much smaller meals, such as plankton and fish no longer than a few inches.
One of the most persistent myths regarding octopus and squids is that of the giant squid -- a massive creature who sinks ships and feasts on humans. Its aggressiveness and predatory behavior as envisioned by authors like Jules Verne is the stuff of legend, but the giant squid does exist. As of 2013, the largest one on record was 43 feet long. These squids are seldom observed alive, and typically they can be studied at length only when a corpse is discovered. Sperm whales have been discovered with battle scars apparently inflicted by the suckers of giant squids, and with squids' beaks in their stomachs. This indicates that although giant squids might be formidable fighters, they are not the biggest, strongest or most dangerous creatures in the ocean.
Tom Ryan is a freelance writer, editor and English tutor. He graduated from the University of Pittsburgh with a degree in English writing, and has also worked as an arts and entertainment reporter with "The Pitt News" and a public relations and advertising copywriter with the Carnegie Library of Pittsburgh.