A while back I posted a book excerpt explaining how to defend oneself against a charging land octopus. It advised throttling them at the neck. But it turns out there's a more effective, and less violent, method to deal with belligerent octopuses: hypnotism.
Fig. 1: The proper Danilewskian method for
hypnotizing small to medium sized octopuses.
The earliest known work on octopus hypnotism was done by professor Vasily Danilewsky* of Kharkiv University as part of his research on animal hypnosis, particularly the induction of cataleptic states. His original paper on the subject was communicated in 1878, in Russian. I haven't been able to find that, but I did find a later paper, "Recherches physiologiques sur l'hypnotisme des animaux" ["Physiological research on hypnotism of animals"], that he delivered in French at the first International Congress of Psychology in Paris, 1889 (at the August 9 meeting dedicated to hypnotism, published in the proceedings the following year).
In it, he gives an overview of his research, which determined that of the animals he tested, the most susceptible to hypnosis was the octopus:
[p.86] Le plus de succès se présente dans l'hypnose du poulpe (Octopus). Il faut maintenir l'animal dans une position telle, que ses bras soient dirigés en haut sans que les ventouses s'attachent à quoi que ce soit. Tous les mouvements volontaires de réponse ou de défense s'arrêtent entièrement. On peut irriter l'animal par des piqûres à travers la peau, les bras, par l'électricité ou des substances chimiques sans détruire l'immobilité de l'animal; tout au plus obtient-on une faible réaction locale. Cet état hypnotique peut durer plus d'une demiheure, tandis que chez les autres animaux il dure ordinairement de dix à quinze minutes.
[The most success arises in hypnosis of poulpe (Octopus). The animal must be kept in a position such that its arms are directed upwards without the suction cups attached to anything. All voluntary movements of response or defense stop entirely. One can irritate the animal by punctures through the skin, arms, by electricity or chemical substances without destroying the immobility of the animal; at most a weak local reaction is obtained. The hypnotic state may last more than half an hour, while in other animals it usually lasts from ten to fifteen minutes.]
Interestingly, he found that the duration of hypnotic catalepsy in cuttlefish lasted no longer than in other animals, suggesting this susceptibility is unique to Octopoda and not a general cephalopodan trait.
Further research in the 1920s by Dutch zoologist J. ten Cate reproduced Danilewsky's findings. In his paper "Nouvelles observations sur l'hypnose dite animale. Etat d'hypnose chez octopus vulgar is." (["New observations on so-called animal hypnosis. Hypnosis in Octopus vulgaris."] Archives néerlandaises de physiologie de l'homme et des animaux, vol. 13, 1928, pp. 402-406 -- the Google Books copy doesn't appear to include those pages in its snippets), ten Cate confirmed that the key to octopus hypnosis is inverting the octopus while not touching its arms:
Upon holding Octopus vulgaris in the hand in such a manner that the tentacles do not come into contact with the hand or other objects a state of so-called animal hypnosis quickly follows. The characteristics of this state are more or less complete immobility, atony of muscles, and reduced reflex excitability. This characteristic state quickly passes when the tentacles are put into contact with objects.
[English abstract from Psychological Abstracts, vol. 3, 1929, p. 154.]
When held in this position long enough, the octopus entered a profound cataleptic state:
When the octopus was thus hypnotized an arm could be lifted, and when released it fell as lifeless as a piece of rope -- as great a contrast with the normal behavior of an arm as could possibly be imagined. The octopus could be thrown from hand to hand and showed no more reaction than if it had been a football. A heavy pinch with surgical nippers, or even more drastic treatment, was required to awaken it.
[Description from Kingdom of the Octopus by Frank W. Lane, 1960, p. 84.]
Unfortunately, one hoping to use this knowledge for defense against octopod adversaries -- especially larger ones or those that have the environmental advantage of being underwater -- will face the potentially insurmountable problem of how to first get one's opponent upside down and then keep it that way long enough without it's arms touching anything. But if one could manage such a reversal, hypnotism offers a humane way to incapacitate the octopus without causing it pain or permanent harm.
More realistically, hypnotism would probably be better employed in the care and management of relatively docile subjects, such as the gentle O. paxarbolis, than in mortal combat with an enraged, charging land octopus.
And since I can't get enough of it, here's an episode of Kure Kure Takora where Takora the tree octopus finds a book on hypnosis and uses it to make his neighbors steal stuff for him:
[VIDEO DELETED BY GODZILLA, INC.]
* UPDATE: I originally had Danilewsky's name as "B. Danilewsky", as it's listed on his French paper. His first name is actually Vasily (Васи́лий), although French transliterators might disagree(?). Wikipedia has an entry, so I added that too.