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Stomatopod Log Entry: Comparing Stomatopods to Cephalopods Part II (May 7,2002)

Contributors: Dr. Roy Caldwell, "Pandora" (C. Chen), "kalim" (ASJ)

This series of quotes was taken from the mantis shrimp discussion board, where a heated argument about mantis shrimp intelligence versus octopus intelligence broke out. I have deleted most of the posts, with all apologies, because I wanted to keep this note focused on discussions on differences between mantis shrimps and octopuses (as opposed to general discussions on intelligence and the like). Thanks to all in the discussion.

Heck, the people in the ceph forum (including me) would go ballistic if they saw this thread... hahaha. I have a mantis and an octo, and I must say, the contest isn't even close, sorry mantis fans. My mantis is cool to watch and comes out when I feed him...

But my octo sees me across the room and has learned to behave differently around me than my bf and other friends, since I'm the one who feeds him. When I come close, he shoots water out of his tank to get my attention, and he pulses color also, sometimes coming to the surface and extending 3 of it's arms like a dog in begging mode.

I've seen him solve really unusual tasks too, in his effort to escape.

"Intelligence" is task and species based. I know of no octopus that can remember another octopus with which it has fought for a month or more.

I know of no octopus that can be trained to discriminate betwen to very similar colors.

I know of no octopus that can be trained to discriminate between two different e-vectors of polarized light.

There are stomatopods that can do all of these things.

As for observational learning in octopus, I remain a skeptic. THe Italian experiments that were published a few years ago, to my knowledge, have not been replicated. Many of us have tried. When you think about it, why would an octopus evolve such behavior. They are mostly asocial and rarely whould have the opportunity to observe another octopus do anything.

- Dr. Roy Caldwell

The octopus IS solitary for much of their life, but no more so than a mantis shrimp! There is a social theory of learning for human evolution, but this is not necessarily the only way to evolve complex behavior and cognitive ability (in hominid evolution, there's also a number of competing theories and no real definite consensus in anthropology yet). If you used "being social" as a measure of intelligence, you'd exclude many animals known for their intelligence, including the orangutan, which lives alone most of it's life except when mating or raising young... and of course, you'd exclude the mantis shrimp which can't be known as "social" either! As I said, I have nothing against mantis, I own one myself and have seen it do very amazing things, but owning an octopus also, I've got to say the latter wins hands down.

- Pandora

My statement about octopus not being social had nothing to do with arguments about the evolution of "intelligence" in social verse non-social species. I was simply pointing out that I could see very little opportunity in nature for octopuses to learn by watching one another. Aside from brief mating encounters, most species that have been studied rarely spend much time within sight of another octopus.

As for mantis shrimp, they are indeed much more social than octopus. They frequently occur at very high densities, learn to recognize individual neighbors with whom they frequently interact, and in species such as Lysiosquillina maculata, a male and female may live together for 20 years or more. There is good evidence that these pairs coordinate their activities.

I will admit that I did include sensory systems that octopuses are deficient in, but length of memory is a measure that can be applied across apecies and I can't remember any demonstration in octopus that memory persists as long as it does in stomatopods.

FInally, I will stand my ground on the statment that the Itailian observational learning study has not been replicated using O. vulgarus or any other octopus. I've tried, I know several other cephalopod behaviorists who have tried it, and the effect is not robust. (It didn't work with stomatopods either.)

- Dr. Roy Caldwell

My opinion is that a relatively long-lived critter with intricate and vigorous conspecific social interactions is more likely to evolve behavior and characteristics that are conducive to the development of "intelligence", than a short lived group of animals who live solitary lives. However, that doesn't mean i automatically think that mantis shrimps are intelligent...


BTW, you are wrong about a few other things... in addition to some cephalopods being highly social (i.e. squid), there are long lived cephalopods such as the nautilus, which live for 16 years. We do not know which, the octopus, nautilus or squid is most like the ancestor of all cephs, but the nautilus, being a "living fossil" does make probably the best model. Lastly, on no parental care... look up octopus and parental care and I think you'll find more info Or better yet, ask some of the people here on RC who have bred them. The mothers are often exceptionally good parents, refusing food while rearing young, and of course, ultimately dying for their reproductive success.

...And if you don't have a chance to find these at the library, here's some stuff on the internet you can read right now:

Or just ask Gono, I'm sure he knows a thing or two about octopus rearing and their parental care

- Pandora

If we are moving towards a discussion of parental care, stomatopods certainly engage in far more of it in both quality and quantity. Just a few highlights of things that some stomatopods do that octopus don't.

  1. Care of larvae as well as eggs.
  2. Multiple broods - perhaps as many as 20 or 30 breeding episodes in a life-time.
  3. Monogamy, breeding with the same partner for up to 20 years.
  4. Biparental care with both males and females tending eggs and larvae. In fact in Pullosquilla and some Nannosquilla, the female lays two clutches of eggs, one that the male tends and one that the female cares for.

Some octopus may stop eating for several months and waste away, but some stomatopods also quite eating for months - and they don't die when the eggs hatch.

- Dr. Roy Caldwell

kalim, hehe, I should have never even gone down the slippery slope of parental care to begin with, I only mentioned it because YOU originally brought it up in comparison... it's really not a relevant subject to cognitive ability (unless observational learning and mimicry are directly related to it).

Also, I would definitely agree with you on the part about broad-based claims and the very general idea of "what intelligence is". I will certainly give you that there is more evidence for stomatopods recognizing others, after all, they as a whole more social than octopus (though the word is still out on a number of squid which do show recognition, but as I said, based on evidence alone). But I didn't ask for that... I asked for evidence of observational learning. Look this term up, it has a very specific meaning. I would be extremely surprised if ANY invertebrate had been documented conclusively to learn by observation... the closest studies have all been done on octopi, and I would doubt THAT claim as well, because they were not well-designed studies.

I think the point is that we do all agree that both animals exhibit different aspects of intelligence, we are just disagreeing on what to put emphasis on. I could just as well ask for evidence of mantis spatial mapping, or of neurophysiologic studies on frontal lobe development in mantis, nerve conduction studies, or shape encodement and memory. There is a paucity of evidence on both sides (in different specific testible realms of intelligence), not necessarily because either animal is incapable, but sometimes because the studies have not been done yet, again a limitation of humans. On that respect, I'd certainly be interested in what Dr. Caldwell has to say, since he's done research with both.

- Pandora

let's make it simpler:

  1. we agree that intelligence is an amorphous, broad term that is very hard to measure accurately, if at all.

  2. we agree mantis shrimps are social animals (at least in some cases) with well-developed parental care (at least compared to octos), behavior and learning abilities that equals if not surpasses those in octopus (at least according to Dr Caldwell, who studies both), highly developed ability to distinguish between individuals, are relatively long -lived, and have the capacity to develop monogamous long-term relationships. Octopuses, on the other hand, are asocial short lived species that seem to demonstrate some capacity for observational learning (although this is highly debated even at this time). They also demonstrate a great capability of escaping from tanks.

  3. we agree intelligence cannot be automatically assumed based on such characteristics as monogamy, parental care, etc.

  4. we agree that there are several possible causes for the evolution of intelligence. Two you mentioned: prey/predator selection pressure, and sociality. We agree that both mantis shrimps and octopuises are subject to the first, but that mantis shrimps are alone subject to the second.

    What I think:

  5. I do not believe ascribing so easily the broad term intelligence to mantis shrimps OR octopuses is helpful or even desirable. I believe some researchers get too attached to their subjects and start out by reaching the conclusion of intelligence then trying to prove it.

  6. I find anecdotes about octopuses escaping from tanks and opening jar lids to be interesting stories, but indicative of nothing else. These are probably emergent properties/characteristics that derive from behavior that the octopuses have evolved in their natural habitat., with no higher cognitive forces at work.


Well with those sentiments, I can mostly agree! There are some minor points in the above that I wouldn't go with, but I don't think they're worthwhile splitting hairs over... and the last point is more one of personal opinion which neither of us is really going to have our minds changed over.

- Pandora


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