Keeping an Octopus vulgaris
Keeping an Octopus vulgaris
Written by Monday, 31 March 2003 00:00
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“Thinking of keeping an octopus? Consider their positive attributes; interesting behaviour, colour changing ability, splendid appetites. But then remember the following problems; inking, super-aggressive predation, and Houdini-like escape potential. They eat or will try to consume most everything, will get out of any opening big enough to squeeze their beak through (or push the top off of), and will unknowingly commit hari-kari if spooked into inking their environment. Other than that, cephalopods make good to suitable specialized aquarium specimens.”(1)
When this notion comes from one of the most respected authorities on marine fish keeping one needs to pay special attention to it. It actually sounds like a “no – no” case and it really is. However, once you get an octopus in your tank you realize that those positive attributes mentioned above are an understatement. At the same time you sincerely hope and pray that the list of problems is an understatement, too, which it largely isn’t.
Our octopus (already named Thanassis) was found at a depth of less than 2 meters off the Attica coast on June 24th, 2002 and is the most recent addition to our Mediterranean marine tanks. When we met each other it was sitting relaxed in front of its cave holding a shell. It immediately tried to withdraw in the cave but not quickly enough. I was able to catch it with my hands and place it in the collection bucket we always have when swimming. After getting out of the sea John and I decided that, since we had a rather empty 140 litre tank perhaps we could give it a try – John always wanted to keep one of them anyway. All bathers were surprised to see us changing its water every now and then (instead of killing it on the spot) since it used to release ink every time we removed the cover to make sure it was still alive. We already knew (from Robert Fenner’s book) that inking is very dangerous for its own health in the limited volume of water it was in. We also decided to collect some sea urchins which were supposed to become its first meals.
When we reached home we opened the bucket and tried to annoy it enough in order to release as much ink as possible in the bucket and not in the aquarium. This wasn’t that difficult and after a couple of minutes all ink was released while the octopus, showing an overall light gray / white colour (sign it was afraid) was released in the tank. It immediately disappeared behind the rocks. We also dropped all the sea urchins in the tank and stayed there for a good 2 hours looking at a completely motionless tank. We knew it was alive because of its respiration (the whole head moves with each breath so you can’t go wrong) but it made no effort to move. After leaving the tank alone for an hour we came back to see if anything had changed. Well, the octopus was already patrolling its new house and when it saw us, instead of retreating it became a deep brown / red colour (the “angry” version) expanding all tentacles still moving around. Unless you see this creature moving in a well aquascaped tank you can’t imagine the meaning of the word “flexibility”! It can pass its big body through openings which seem far too small for it in an effortless way. Of course, we already knew about the Houdini-like escape potential so we covered the tank with a peace of Styrofoam cut to shape and placed several heavy rocks on top of it.
Next day it was obvious that night is the best moment for this animal (being a nocturnal hunter). Regarded one of the most able and deadly predators in the animal kingdom it had already eaten all the bivalves in the tank and a small fish which was discovered under a rock. However, the sea urchins were still there. The octopus seemed more relaxed moving around, even swimming in a couple of occasions (mainly testing the dimensions of its new sheltering den), while re-decorating the tank to meet its own needs. We decided to wait a bit longer to make sure that it would not eat the urchins before adding other food in the tank. With a tank this size you have to be very carefully not to pollute the water.
Indeed, after 4 more days, it was clear that sea urchins was not its favourite dish so we had to go for something else. The octopus was really hungry and only accepted a piece of fish meat (after examining it for some time) while a frozen shrimp was caught at first but immediately rejected. By the way, you have to remove the uneaten food quite fast – since octopus already produces enough (very concentrated) urine to pollute any under-filtered tank. With an octopus in the tank this is easier said than done. First comes the cover which has to be removed again. Then comes the octopus itself which – if frightened – will release its ink. So, you have to work quickly but smoothly while your moves inside the tank must be as less threatening as possible. The octopus watched the long tonsils with curiosity from the “safety” of its cave. Even though there was a 40 cm distance, it became brown/red again while it changed its skin texture from smooth to wrinkled. Anyway the shrimp was out without ink in the tank although we had half a kilogram of super activated carbon ready to be used – just in case …
We then placed an order to our nearby fisherman for live mussels which would have to be collected only hours before we got them. He was extremely interested in the well being of the captive octopus and called us at 6:00 am to let us know that the mussels were collected and we should go and get them.. Six o’ clock in the morning is not the best time for me but fish keeping means sacrificing some things.. like those extra two hours of sleep. All mussels were placed in the left tank so the octopus (occupying the right tank) would not eat the lot at once. We then lifted the cover of the right tank and – with the lights still off – dropped four mussels in its tank. I must confess I never expected the octopus to be so lightning fast. In a fraction of a second it moved from its cave and grabbed two of the mussels in mid water. The animal seemed to be really hungry. It didn’t even pay attention to us as it immediately opened one of them and ate it on the spot. After that it took another one and went back to its cave.
Its behaviour is now more close to what we observe in its natural environment. It will come out of its den, walk around and then take a mussel (if hungry) and get back to its “den”. Actually it has created its own little home after spending the first couple of days in a pot we had provided it with. Instead of using it the octopus got two stones (quite heavy ones) put them on the two sides and then used the already existing ones as the “front” wall of the home. Just before going to sleep, it will also take some mussel shells and put them over it. When sleeping, the head is almost hidden under the shells. When awake the head is over the shells watching every single move we make. It knows exactly when the cover is to be lifted and will eagerly come to take the mussels. Of course, the octopus in the wild relies on a more varied diet and this is the next thing to ensure. Every week we bring back from the sea live small crabs while there is a quantity of swordfish fillet in the fridge to wet its appetite.
The sight of it coming to you immediately to beg for food is something that you have to see in order to believe. Not only will it come close (no ink..) but it will grab your hand as well as anything that falls in the tank in the hope it is some kind of food. Sometimes it will stay in the surface, all arms extended with its head in the water (upside down) until it realizes there will be no (more) food. When a piece of food falls further apart it will extend one of its arms in a straight line and then use the suckers that come in contact with the food to test it. When it realizes that this is something edible it will immediately take it and bring it to its mouth. When it opens a mussel you can hear the sound of the opening shell very clearly. After we added some prawns in its tank it spent days “playing” with them, trying to catch them using every possible way. We saw it using the “surprise attack” by suddenly expanding its whole body and arms to catch them. When this failed, it was time for the “ambush” approach by taking the colour of the sand and remaining absolutely motionless till the prawns came near to it, at which time it would prepare the arms not visible by the prawn to make the attack. It then used the “slow approach” technique – by crawling on the sand and then on the glass in a seemingly airy way. When all that failed it simply decided it can coexist with them so now you can see prawns even sitting on it.
One thing that needs to be taken care of is filtration. The octopus has very effective kidneys which are able to concentrate urine unbelievably. Apart from that, it should be the definition of “messy eater”. Not only does it spread the food all over the place but then uses its siphon to clean up itself and the place it is sitting on. You can then imagine hundreds of small food particles floating around the tank all the time. Prawns will make a good meal out of them but still a great deal will have to be collected by the filter and the skimmer. I would advice the use of a good skimmer rated for at least 3 times the volume of water you have and a good filtration system. Periodically cleaning the filter cartridges with synthetic sea water is recommended. I would suggest that you look at the outlook of your power filter every day to make sure it is not clogged. With this kind of mess this will happen much sooner than anticipated.
After spending some time with it we can’t really tell if it is really that intelligent but it is definitely different. In contrast to most other marine species we keep which react in a predictable pattern the octopus will react in its own way – a different way every time. It may or may not come in the front glass, change the colour or the texture of its skin, or simply ignore us and continue doing what it was already up to – and most of the time it is up to something. We have seen it using the thin ends of its tentacles to “scratch” itself, to examine the glass heater closely, to check the dimensions of the place it was about to settle, to create a new “home” in an instant by grabbing what is available within reach (even if this is the two sea stars – an unforgettable sight – can you imagine it being “hidden” behind two bright red sea stars?) and many more actions that indicate it is able to make a decision and execute a plan very quickly. The ability to use its arms in almost the same manner we use our hands gives this animal a more “human” like behavioural appearance. You expect it to take something and – most important – “use it” which makes it unique. Moreover, although it is supposed to be a nocturnal and shy animal this is not the case when it gets used to its surroundings and feels safe. After a week in captivity you will never see it getting afraid or running for shelter.
There are many people who have run numerous tests to evaluate the intelligence of this animal and the general belief is that it is one of the most intelligent animals on this planet. Some of these experiments show beyond any doubt that the octopus is able to think, plan and perform the task in the most efficient way. This was further proven in an experiment with bivalves which needed varying force to be opened or presented in different ways to the octopus. The animal was always able to select the correct and most efficient way to open them. Two of these scientists, Jennifer A. Mather and Roland C. Anderson have commented the following:
“When humans think of intelligence, we think of ourselves. This anthropocentric viewpoint is partly because intelligence has only really been studied in vertebrates and partly because we see its evolution as leading to the pinnacle called Homo sapiens. Until recently, there hasn't been any model of how another completely separate group could show us how intelligence might evolve differently than ours. Research on the octopuses is beginning to provide that alternate model.” (2)
This is definitely so and we all know that whenever we look at our pets (being them fish or any other species) we are trying to interpret their emotions based on how we would feel if we were in their position. Moreover, we try to think that they “feel” the same as we do, express themselves the same way and finally react in a similar - even if more simple - pattern. However, deep inside we know that things are not that simple. Our pets are different to us. How different? According to those two authors, maybe not much different.
“Perhaps it is this individual sensitivity to change, honed by intelligence and variability, that has been the key to the success of both the cephalopods and the higher vertebrates. Similarities that could lead us to understand the evolution of intelligence in octopuses and humans are few, but thought-provoking: 1) neither group has the protection of exoskeleton, scales or armour, 2) both have evolved in complex environments, the octopod in the tropical coral reef and the hominid in the savanna edge, and 3) both have considerable variability among individuals and the ability of being able to change their behaviour to help them survive. So, perhaps looking at the octopuses through their intelligence, feeding flexibility, predator avoidance, play, and personality helps us also look at aspects of ourselves, from another angle!” (2)
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