I was stirred to write this aticle when a friend sent me new footage of a mimic octopus in Indonesia. It’s a common scene. The octopus is sitting at its den entrance. It takes hold of the diver’s slate and the diver uses this to try to slowly tease it out to the open sand. But then before you know it, the octopus reaches for the diver’s bare hand, pulls the fingers in slowly, slowly, and eventually its beak is right over the diver’s hand. As the arms and mouth delicately feel around the hand, all I can think is “Don’t bite, Don’t bite!” and “Ack! Why in the world are you letting that octopus crawl all over your bare hand?! It could be dangerous!!”

Picture this: You’re on vacation, and you find a pretty tropical spider on the railing where you’re drying your towel. Would you let that spider crawl all over your bare hand?

Most people would answer “no” to that question. Most of us have such a minimal understanding of spider venom diversity and spider behavior that we don’t assume by default that it could be safe to handle. We would gladly, and probably safely, watch one in its web, but would think it’s crazy to let it crawl onto our hands. Even though every day people all over the world dive with cephalopods, it’s a good idea to treat them the same way you would a spider; with awe, but from a distance.

Here are the most common reasons people give me for choosing to handle cephalopods, and some serious reasons why you should not.

But I didn’t know Cephalopod X could be dangerous

Dive under the assumption that any cephalopod could have a dangerous or painful bite, especially in the tropics. For most cephalopods, including the Mimic Octopus and Wunderpus, the venom has not been analyzed by scientists, and there are no publically available reports of people being bitten. We simply have no idea how dangerous they could be. Scientists, divers, fishers, and aquarists continue to discover new species each year, especially for diverse regions and favorite dive spots in Asia, Australia, and Oceania. Even if a cephalopod has a scientific name or has appeared in dive magazines, that doesn’t mean we have an understanding of its toxicity. Toxicity studies are very expensive, time consuming, and are usually done only after a species is suspected or known to be toxic. Don’t be the first to get bitten. Don’t test the venom for yourself.

But so-and-so heard of this guy who was bitten, and he was fine. Ok, so it hurt a bit, but he didn’t die.

Even if you personally know a population of cephalopods very well and are 100% sure that people along that very same coastline have been bitten and survived bites, you could have a unique adverse reaction of your own. Like spiders, all cephalopods known so far have some form of toxic venom used to immobilize and/or help kill their prey, but the strength and the chemical mixture of the toxin(s) vary both within and between species. Some cephalopods also have toxins throughout their body in addition to their saliva, making them poisonous to eat in addition to having a venomous bite. Your own body’s reaction to those toxins ultimately determines how dangerous a cephalopod is to you. Even if a bite isn’t dangerous, many people have undesirable reactions. Do you really want your arm to swell up while you’re on vacation, or risk the bite getting infected?

But it was just such a nice octopus!” or “That kind never bites!

Some cephalopods show evidence of personality, so some individuals may be more or less likely to bite you than others. But for the most part, many cephalopods you encounter on a dive are generalist predators that are looking for their next meal, while simultaneously trying not to be eaten themselves by something larger. If some living part of you gets near a cephalopod’s mouth, it has every reason to bite and few reasons not to. If you handle it, it may bite you out of defense because you are so much larger. If you try to lure it out of its den, it might mistake your hand for a meal. I have seen octopuses lunge at, seem to bite, and not let go of items that would seem much less edible than a finger. Many cephalopods manipulate their prey before biting. If you get the impression that an octopus is “playing” with your hand, it might just be trying to reposition you into a good biting angle. It may give up and let you go, or it may bite.

While some people have gained lots of experience safely handling certain cephalopods, some species of cephalopod are often handled without biting people, and some people get bitten but don’t feel much pain, the reality is if you handle a cephalopod there’s always a chance it will bite, and there’s a good chance if it does it will hurt you. The best way to be sure a cephalopod doesn’t bite you is to refrain from handling it.

What cephalopods are known to be dangerous or have painful bites?

Blue-ringed octopuses (genus Hapalochlaena) have dangerous neurotoxins in their venom and their bite has killed people. Of the numerous species of Blue-ringed octopuses that exist, some populations might not be deadly, but it’s best not to risk it. Relatives of the “day-drop-arm” octopus (Abdopus aculeatus, a.k.a. “Shaggy octopus” or “Algae octopus”) have a neurotoxin in their tissues that is similar to tetrodotoxin (TTX), the chemical that makes Blue-ringed octopuses and fugu (pufferfish) so deadly. The Poison Ocellate octopus (Amphioctopus mototi) is, you guessed it, venomous (toxin ‘administered’ through a bite) and could be poisonous (toxin acts if ingested). The Eastern Pacific Red octopus (Octopus rubescens), Giant Pacific octopus (Enteroctopus dofleini), Common Reef octopus (Octopus cyanea), Ornate octopus (Callistoctopus ornatus) and Common octopus (Octopus vulgaris) have given people very painful bites when handled. Giant cuttlefish (Sepia apama) and the Humboldt squid (Dosidicus gigas) have acted aggressively toward divers, though it’s unknown what may have sparked this behavior. This list is not exhaustive. Please do feel free to write in to contribute your own cephalopod bite experiences.

Some other cephalopods are thought to be especially venomous based on their body colors or other unpublished information. Flamboyant cuttlefishes (Metasepia spp.), Wunderpus (Wunderpus photogenicus), the Mimic octopus (Thaumoctopus mimicus), the Striped Pajama Squid (Sepioloidea lineolata), the Pacific Striped octopus (Octopus chierchiae) and the Larger Pacific Striped octopus (undescribed) fall into this category.

Special note about Blue Ringed octopuses.

Blue-ringed octopuses are very small. Their mantle (body sac) can be about the size of a grape, and they can fit into tiny spaces. While you dive or snorkel in their home range, be careful not to pick up and carry around things in which they could be hiding, such as empty shells (including cowries, conchs, and cone snails, etc.), cans, bottles, or anything else with little holes and pockets. If you inadvertently pick up a Blue-Ringed octopus’s home and it doesn’t come out during the dive, then it will come out on the boat, or in your shorts pocket if that’s where you’ve held the shell.

Touching them could hurt them:

In addition to protecting yourself, please also think of the cephalopods, and don’t touch them. Cephalopods have sensitive skin and poor immune systems. Skin lesions can become infected and turn deadly. Please treat them the way you would a whale shark, a sea fan, a manta ray, or any other delicate animal we already know not to touch for their protection.

Further reading:

*While not all scientific papers are freely available on the internet, in most cases the corresponding author can email you a pdf of the paper upon request.

1. Reynolds, S. Cuttlefish Attacks on Divers. Paper available on the web
2. *Williams, B. L., & R. L. Caldwell. 2009. Intra‑organismal distribution of tetrodotoxin in two species of blue‑ringed octopuses (Hapalochlaena fasciata and H. lunulata). Toxicon 54(3):345–353.
3. Norman, M. D. 2000. Cephalopods: A world guide. ConchBooks, Hackenheim, Germany.
4. Nature, Kings of Camouflage. Paper available on the web
5. Tonmo.com
6. *Robertson, A., D. Stirling, C. Robillot, L. Llewellyn, A. Negri. 2004. First report of saxiton in octopi. Toxicon 44, 765–771.
7. *Fry B. G., K. Roelants, J. A. Norman. 2009. Tentacles of venom: toxic protein convergence in the Kingdom Animalia. Journal of Molecular Evolution 68(4), 311-21.
8. *Sinn, D. L., & N. A. Moltschaniwsky. 2005. Personality traits in dumpling squid (Euprymna tasmanica): Context-specific traits and their correlation with biological characteristics. Journal of Comparative Psychology, 119, 99–110.
9. *Huffard, C.L., N. Saarman, H. Hamilton, & B. Simison. 2010. The evolution of conspicuous facultative mimicry in octopus: an example of secondary adaptation? Biological Journal of the Linnean Society, 101(1):68–77

About the author: Crissy Huffard is a cephalopod biologist and marine conservation consultant based in California. Over the years she has published research papers on bipedal locomotion in octopus, photo-identification in Wunderpus, evolution of the Mimic octopus, and other topics in marine science. Her work has taken her from the Equator Islands in Indonesia to the icebergs off Antarctica, and many coastlines in between. In her most recent role Crissy worked for over three years with local marine conservation teams in Raja Ampat and Kaimana, Indonesia to provide science support to multi-use marine protected areas, aiming to help protect community fisheries and food security.