As a follow-up to my previous post about Oppian's poetical description of olive-loving tree octopuses, here are the other surviving reports from the Old World of octopuses coming out of the seas and and going into the trees...
In his History of Animals, Aristotle notes in passing that "the octopus is the only mollusc that ventures on to dry land; it walks by preference on rough ground". This, of course, isn't true: snails and slugs are all mollusks who have also ventured out of the sea. However, Aristotle's confusion over the membership of the phylum Mollusca notwithstanding, this does show how land-going octopuses were well known in the ancient world.
Pliny the Elder repeats in Naturalis Historia the observations (first published by Trebius Niger) of Lucius Lucullus, the proconsul of Hispania Bætica, who described a giant polypus (an older term for octopus) that was terrorizing Iberian fish-picklers by coming out of the sea and robbing their salty stores. This story is particularly notable to tree octopus fans since the thief used a tree to gain entry:
At Carteia, in the preserves there, a polypus was in the habit of coming from the sea to the pickling-tubs that were left open, and devouring the fish laid in salt there -- for it is quite astonishing how eagerly all sea-animals follow even the very smell of salted condiments, so much so, that it is for this reason, that the fishermen take care to rub the inside of the wicker fish-kipes with them. -- At last, by its repeated thefts and immoderate depredations, it drew down upon itself the wrath of the keepers of the works. Palisades were placed before them, but these the polypus managed to get over by the aid of a tree, and it was only caught at last by calling in the assistance of trained dogs, which surrounded it at night, as it was returning to its prey; upon which, the keepers, awakened by the noise, were struck with alarm at the novelty of the sight presented. First of all, the size of the polypus was enormous beyond all conception; and then it was covered all over with dried brine, and exhaled a most dreadful stench. Who could have expected to find a polypus there, or could have recognized it as such under these circumstances? They really thought that they were joining battle with some monster, for at one instant, it would drive off the dogs by its horrible fumes, and lash at them with the extremities of its feelers; while at another, it would strike them with its stronger arms, giving blows with so many clubs, as it were; and it was only with the greatest difficulty that it could be dispatched with the aid of a considerable number of three-pronged fish-spears. The head of this animal was shewn to Lucullus: it was in size as large as a cask of fifteen amphoræ, and had a beard, to use the expressions of Trebius himself, which could hardly be encircled with both arms, full of knots, like those upon a club, and thirty feet in length; the suckers or calicules, as large as an urn, resembled a basin in shape, while the teeth again were of a corresponding largeness: its remains, which were carefully preserved as a curiosity, weighed seven hundred pounds. [Chapter 46, Book 9.]
Aelian's On the Characteristics of Animals contains a similar encounter with a pickled-fish-marauding octopus that took place in the Greek colony Dicaearchia -- this one using the sewers instead of a tree to infiltrate a human settlement, but worth quoting nonetheless:
Octopuses naturally with the lapse of time attain to enormous proportions and approach cetaceans and are actually reckoned as such. At any rate I learn of an octopus at Dicaearchia in Italy which attained to a monstrous bulk and scorned and despised food from the sea and such pasturage as it provided. And so this creature actually came out on to the land and seized things there. Now it swam up through a subterranean sewer that discharged the refuse of the aforesaid city into the sea and emerged in a house on the shore where some Iberian merchants had their cargo, that is, pickled fish from that country in immense jars; it threw its tentacles round the earthenware vessels and with its grip broke them and feasted on the pickled fish. And when the merchants entered and saw the broken pieces, they realised that a large quantity of their cargo had disappeared; and they were amazed and could not guess who had robbed them: they saw that no attempt had been made upon the doors; the roof was undamaged; the walls had not been broken through. They saw also the remains of the pickled fish that had been left behind by the uninvited guest. So they decided to have their most courageous servant armed and waiting in ambush in the house. Well, during the night the Octopus crept up to its accustomed meal and clasping the vessels, as an athelete puts a strangle-hold upon his adversary with all his might gripping firmly, the robber -- if I may so call the Octopus -- crushed the earthenware with the greatest ease. It was full moon, and the house was full of light, and everything was quite visible. But the servant was not for attacking the brute single-handed as he was afraid, moreover his adversary was too big for one man, but in the morning he informed the merchants what had happened. They could not believe their ears. Then some of them remembering how heavily they had been mulcted, were for risking the danger and were eager to encounter their enemy, while others in their thirst for this singular and incredible spectacle voluntarily shut themselves up with their companions in order to help them. Later, in the evening the marauder paid his visit and made for his usual feast. Thereupon some of them closed off the conduit; others took arms against the enemy and with choppers and razors well sharpened cut the tentacles, just as vine-dressers and woodmen lop the tips of the branches of an oak. And having cut away its strength, at long last they overcame it not without considerable labour. And what was so strange was that merchants captured the fish on dry land. Mischief and craft are plainly seen to be characteristics of this creature. [Chapter 6, Book 13. Translation by Alwyn Faber Scholfield, 1958.]
Aelian also mentions the olive-loving semi-arboreal octopuses that Oppian described:
Fisherfolk assert that even octopuses come ashore if a sprig of olive is laid upon the beach. [Chapter 37, Book 1.]
If a field, or if trees with fruit upon them are close by the sea, farmers often find that in summer Octopuses and Osmyluses have emerged from the waves, have crept up the trunks, have enveloped the branches, and are plucking the fruit. So when they have caught them they punish them. And as quittance for what the aforesaid fish have reaped they provide the owners of the pillaged fruit with a feast. [Chapter 45, Book 9.]
These olivevorous tree octopuses are also described by Athenaeus in his Deipnosophistae ("Banquet of the Learned"), who adds figs to their diet:
And sometimes they [polypi] have been seen leaving the sea, and going on dry land, especially towards any rough or rugged ground; for they shun smooth places: and of all plants they especially delight in the olive, and they are often found embracing the trunk of an olive with their feelers. They have also been discovered clinging to such fig-trees as grow near the seashore, and eating the figs, as Clearchus tells us, in his treatise on those Animals which live in the Water. And this also is a proof that they are fond of the olive, -- that if any one drops a branch of this tree down into the sea, in a place where there are polypi, and holds it there a little time, he without any trouble draws up as many polypi as he pleases, clinging to the branch. [Chapter 103, Book 7.]
From these stories and descriptions we can piece together a possible history of Old World tree octopuses: Being naturally curious, the octopuses cautiously explored the sewers and other manmade waterways in search of the fish they no doubt saw humans take from the sea. Upon finding the fish, they became emboldened by the added deliciousness of the pickling process, and were willing to risk venturing across dry land to get to the preserves. When humans tried to stop them with walls, they quickly learned to use the trees to their advantage. This led to their discovery of olives and figs, with which they quickly became so enamored even pickled fish no longer interested them.
Could humans have played a similar role in the evolution of the Pacific Northwest Tree Octopus? Perhaps octopuses originally came ashore looking for the salmon they saw humans catching. When they discovered the humans' smoked salmon -- so unlike the fish they were used to, and so very, very tasty -- they wanted more than they could steal from the humans, and thus took to the similarly flavored redcedar trees under the mistaken belief that "tree fish" -- naturally imbued with the smoky redolence of the woods -- dwell there. Not ever finding these mythic fish, they eventually gave up their quixotic search, but, having become accustomed to their arboreal life, continued to call the trees home.
Well, it's one possible explanation, anyway.