Are tarantulas intelligent

Eight-legged geniuses

Octopods and spiders fascinate with their high intelligence, which arises from completely different brains

Is it because of the legs? Probably not. But an impartial observer - for example from a strange planet - who wanted to find out which animals are particularly intelligent and why, could establish all sorts of correlations and come to the conclusion that as soon as one leaves the realm of the vertebrates, intelligence is at its maximum with eight legs reached: octopods and spiders.

In fact, it will be a coincidence. Another connection is more conclusive. Vegetarians have to be very brave now, but it is like this: If you look around the animal kingdom, the hunters are usually brighter than the herbivores (and plankton). Toothed whales beat baleen whales (not to mention manatees), wolves beat sheep, box jellyfish beat moon jellyfish, ravens beat chickens. This is simply due to the different requirements of food production. You don't need to surround a green pasture, you don't have to trick krill, you don't have to stalk a ripe apple, and you don't have to be careful that the kale doesn't see you. It is the hunt that calls for strategy formation, foresight and a change of perspective.

But it is the eight-legged hunters who fascinate the most. They are like aliens who live among us; independently evolved intelligences whose last common ancestor lived with us around 560 million years ago - or even earlier - and was so simply structured that an earthworm looks like Einstein in comparison. From a few nerve tracts distributed over the body and an eye spot, a powerful brain was created several times, which can grasp, learn, plan and remember its environment with several senses.

Octopods: Mentally and physically flexible

The octopods (and their ten-armed relatives, the cuttlefish and squids) are similar to us and therefore perhaps more understandable in that they combined intelligence with brain size. And their pupilized two lens eyes may also help us to come into eye contact with them.

An octopus' brain is about the size of a rat, but probably more powerful. He easily acquires the ability to open a lid jar - if there is a living cancer in it. The mollusc also copes with the problem of maneuvering the clasped crab through a narrow neck of a bottle. And if an octopus cannot solve a task right away, then it is able to see how it works from a neighbor in the aquarium. This learning by imitation, and the excitement that the animal shows in it, seems very human. And so the octopus seems understandable.

But only at first glance. The scuba diver and philosopher Peter Godfrey-Smith pondered in a very readable book ("Other minds") what it might mean for the self-perception of an animal that a third of the nervous system is in the legs, so that each leg can even make independent decisions can meet. Does such an animal have a clearly defined self or does it feel more like a body?

And how can we imagine high intelligence without tradition? And anyway: in such a short life? All cephalopods don't live longer than a year or two. Many still tend their brood. But they die when it hatches. Little octopuses can learn nothing from their parents, nothing they pass on to them. If it were different, maybe the octopods would have taken over the world long ago. But without brood care and a family, no social associations, no altruism, no cooperation could develop. Each octopus hunts and dies for itself.

Nevertheless, their intelligence is striking. Octopods are feared as escape kings in aquariums. That they can maneuver their soft body through even the smallest holes helps them. And they also have a downright malicious sense of humor. Smith tells of captured octopods who shot out the light bulb in the room with a targeted jet of water from their siphon. Or even such a jet of water in the neck of a zookeeper they didn't like.

A story from Smith's book sounds so incredible that I have to retell it here. He emphasizes that he got it from a respected, soberly observant researcher. She went down the aisle with the aquariums and fed the octopods with thawed pieces of cuttlefish. Octopods eat something like that, but they don't like it. They prefer live crabs. The researcher noticed that the octopus in the first basin did not eat its ration, but held it in a wait-and-see manner and followed it with its eyes. She returned from the end of the corridor and the animal was still watching her. And when she was next to his aquarium, he took the unloved pieces of food - and threw them into the overflow of the aquarium.

Coincidence? Overinterpretation? Maybe. But actually you don't want to see it that way.

The world in the spirit of the spider

While octopods seem familiar and likable to us with their size, their softness and agility, their sociable curiosity and, last but not least, their play of colors (which the ten-armed cuttlefish have perfected), none of this applies to the other eight-legged creatures: spiders. Most of us - even I have not yet completely overcome a slight arachnophobia - are rather happy that the arthropods lack the size of squids as well as their sociability. It is not easy to like spiders. But at least you can marvel at them. And respect.

It was established early on that they are not stupid. The anthology "Invertebrate Learning" from 1973 describes, for example, what happens when you carefully cut off a braided piece of prey that a spider has hung in its web with fine scissors: Then the spider moves around the spot in increasing concentric circles on which the loot had hung. I mean: she's looking for her. So she has an inner representation of her web, and a memory for what should be where in it. And on top of that, a sensible strategy to look for it when it is not there. Recently, this finding has been replicated and expanded: web spiders look longer for large prey than small prey, so they also remember this factor.

But the intelligence beasts among the arachnids are the jumping spiders. They do not spin webs, but roam around to hunt, lie in wait for their prey or sneak up on them, and then catch them with the leap that gives them their name. They only use a spider thread for self-belaying.

This way of life demands flexibility, and jumping spiders do indeed display this trait. Depending on what prey they are looking for, they adapt their strategy: they only attack large prey from behind, while smaller prey from any direction; They hunt fast prey, but sneak up on immobile ones.

Jumping spiders of the species Portia fimbriata perform perhaps the most impressive feats of intelligence. These animals are after a special and delicate prey: other spiders, namely orb web spiders. The obvious problem with this is that orb web spiders constantly monitor every movement in their webs with high sensitivity, making it impossible to sneak up on them. Some species of Portia solve this problem by mimicking the vibrations of captured prey, luring the net owner over to kill it. Others by waiting for a gust of wind to mask their movements, or by shaking the web itself as hard as a blast of air. But none of this works with the highly nervous Australian spider Argiope appensa. And a charge against the defensive opponent would probably not be advisable.

So what is Portia doing? When it spots possible prey, it immediately performs its first remarkable cognitive feat, which others will follow: it does not run away, but pauses and plans. She looks around to see where there is a branch above the prey spider and how to get there. Then she goes there, which implies moving away from the prey. From the point above its prey it then lets itself off with a spider thread and strikes.

To do this, the jumping spider needs an impulse control that is not found even in many birds and mammals. Furthermore, a three-dimensional representation of their environment, which is precise enough to virtually drop the plumb bob over their prey. Then the ability to remember the targeted place and the way to get there until it is there. - Chapeau!

The intelligence in the poppy seed

And all in a brain the size of a poppy seed. Little is known about how this brain crumb produces such cognitive performance. It has been known for a while that there are two separate visual systems in it: with the two frontal main eyes, spiders see sharply and in color (and how they achieve 3D vision despite the tiny interpupillary distance is a topic in itself), with the other three Pairs of eyes, on the other hand, discover movements.

How this information is integrated, however, could not be investigated for a long time because it is not trivial to gain access to the brain of living jumping spiders: Their body fluid is under high pressure, which is used hydraulically for movement. If you drill a hole to put an electrode through, the liquid will squirt out and the animal will die. It was not until a few years ago when different types of electrodes were used that it became possible to observe spider neurons at work and, for example, to find some that respond specifically to moving flies.

In one thing at least, the jumping spiders have recently moved closer to us emotionally: As was recently discovered, at least one species (Taxeus magnus) in this group is suckling its young. Animals that feed their offspring with body secretions in different ways come in different groups. Caecilians, for example, an earthworm-like form of salamanders, deposit layers of skin for this purpose. These jumping spiders, however, literally produce a milky secretion from glands in their abdomen, which is absorbed by their spiderlings and must be in order for them to survive. Ultimately, the mother takes care of her offspring for several weeks until the little ones can hunt themselves and leave the house.

At the end, however, we leave the jumping spiders and return to our familiar, web-building house spiders. Because they can surprise you too. Michael von Tschirnhaus, who was responsible for collection and entomology at Bielefeld University, once exhibited a mason jar into which a house spider had obviously fallen. She couldn't get out because the walls were too smooth. That might be a situation that evolution did not anticipate. So what was the spider doing? She began to weave a ramp, rising in a spiral staircase from the bottom of the glass. If she had had enough spider silk or food, then she would have made it. But as it was, she starved to death halfway and was found on her unfinished work.

Other intelligences

We almost expect great apes and primates to achieve high cognitive performance. And every owner (and only this one) thinks his dog is super-intelligent. The fact that birds also have very bright heads was a little harder to accept. Her brain seemed too different. But then it turned out that it contains the same modules as ours, just arranged differently, and that was all fine. Because we understand the intelligence of vertebrates, monkeys, domestic animals, whales and birds because they are similar to us.

And that is exactly what the spiders and cephalopods break through (and the bees, dragonflies and many others that I have arbitrarily neglected here because of their number of legs). They show that humans are not the measure of all things. That intelligence is also possible in a completely different way. They can orientate themselves spatially and remember and yet have no hippocampus, they have a working memory and strategic thinking, but no frontal lobe, they learn motor skills without any basal ganglia or reward pathway (although a common origin has been claimed here). Evolution has demanded and promoted certain intellectual achievements, and the nervous system was formed in order to produce them. There are different implementations of the same capabilities.

And who knows how many skills are left? We implicitly assume a convergent evolution, i.e. that the same abilities were achieved independently and in different ways. But are they the same skills? Does an octopus think like us? Is he perhaps also coping with completely different achievements that we cannot even recognize because we cannot? Hasn't "the intelligence" developed several times, but rather different intelligences that touch here and there but cannot understand each other?

Man is always looking for himself in his environment. He looks into the eyes of his counterpart and expects a mirror. Empathy is always also projection. But if we look into the eyes of the eight-legged genius, then this search fails. We look into the absolutely foreign. The incessantly fascinating.

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