Are webs part of a spider's mind?

Orb weavers and their webs

Spiders are the masters of weaving silk. But spiderwebs haven’t only been catching spider food; they have also captured the attention of humans. All thanks to a question – Are spider webs part of the spider’s mind? This notion, rooted in cognitive science, philosophy of mind, and spider love, suggests that spiders may use their webs not just as tools but as also as integral components of their cognitive processes.

The subject of this captivating story is the orb weaver. With over 3000 species, these spiders are renowned for their meticulously crafted spiral webs, often found adorning Australian gardens. Something to know about orb weavers is that they have terrible eyesight. Without great vision of the world around them, they rely entirely on their silk for food and shelter (two essentials needed for survival). But the spider’s reliance on the web is not enough to suggest the web is part of the mind – we need to dig deeper.

Orb weaver with newly constructed web in the middle of a busy walkway in an Adelaide inner suburb.

A Tale of Extended Cognition

This question is in part triggered by some recent discoveries in the relationship between spiders are their webs. There is no question that webs are an extremely effective and necessary tool for these blind spiders, in part because it extends their senses beyond what the body alone is capable of. But recent observations have questioned whether this concept can be taken a step forward, moving away from a more traditional to a more extended way of thinking about minds.

Traditional cognition is the mental action of acquiring knowledge and understanding through thought, experience, and the five senses. In this sense, the web is nothing more than a tool for the spider to obtain information, as the mind is limited to the physical confines of the body. However, thanks to scientific observations, some are wondering whether the spiders are actually using their webs as a form of extended cognition.

Extended cognition is information processing and cognitive states that take place outside the nervous system that increase your chance of survival. It can be any processes that act as extensions of our thought, beyond the ability of the body alone (calculators, writing, and phones are considered as elements of human extended cognition). And so, in the case of spiders, their webs could serve as extensions of their minds, facilitating a range of cognitive tasks crucial for survival and adaptation.

Processing, learning, adapting, and remembering through the spider web

It turns out, there is a lot of evidence out there that the silk threads of webs do extend the sensory arrays of spiders and contribute to cognitive processes. Firstly, spiderwebs transmit vital information about the environment to the spider’s awareness. When prey becomes ensnared in the web, the resultant vibrations serve as cues for the blind spider to locate and subdue its meal. Remarkably, spiders also possess the ability to adjust the tension of their web’s strands, to increase the sensitivity to vibrations when hunger strikes. They have also been seen to tailor their web designs to suit what insects they’ve been catching – if they’re having better luck with smaller insects they’ll add more threads; if they’re having more luck with bigger insects, they can reduce the thread count.

Another remarkable discovery is that spiders can exhibit memory using their web. When spiders are finished with a meal, they will wrap up leftover food in silk (it a bit like using gladwrap) and store it on the web for later. It has been experimentally shown that spiders are then able to recall the precise location of their leftover meal – effectively utilizing their webs as memory maps. Memory in invertebrates is rare and has only been shown in a handful of bugs.

The ability to encode, store, and retrieve information from the web demonstrates a sophisticated level of cognitive processing and is a testament to the dynamic symbioses between the silk and their understanding of the world.

Small brain but big behaviours

The last stop on this journey through the spider mind is the size of the spider’s brain. While I couldn’t find an exact figure (and I don’t have any arachnologists on speed dial), my internet search has led me to guesstimate that the brain of an orb weaver is no bigger than a poppy seed. That is a tiny brain – miniscule even. This small brain size is thanks to the evolutionary pressures and tradeoffs on energy demand.

To understand this we can refer to Haller’s rule which states that, while small creatures will have smaller brains, the ratio of brain to body size will actually go up. For example, the brain to body ratio for elephants is 1:560, but is a whopping 1:7 in ants despite being infinitesimally smaller (for reference in humans, our brain to body ratio is 1:40).
Since brains are energy intensive, smaller animals, such as spiders, must navigate a delicate balance between cognitive capacity and energy expenditure. While bigger brains may allow for more complex cognitive abilities, when you’re the size of a spider, the energy you’d need to consume to maintain the big brain just simply isn’t feasible. Yet spiders exhibit what is generally considered to be cognitively intense behaviour.

In fish and mammals, it’s well documented that predators/carnivores have larger brains, relative to their bodies, than their prey. Larger brains are needed for more cognitive tasks – hunting strategies are more intense than grazing. It is also accepted that generalist foraging strategies (not having a strict diet – like animals that only eat 1 food) require enhanced information processing capabilities due to the diverse challenges presented by a wide niche.

Yet despite the small brain, the carnivorous and generalist diet, the spiders are doing it all! This is another reason why spiders are excellent candidates to search for adaptive cognitive strategies like extended cognition.

Spinning tales

The green room loves a story. And this one is a favourite because it’s spinning a tale on mind – literally and metaphorically. By taking our ideas on mind and comparing them with nature’s evolutionary innovations, we can untwine the web that is cognition. Spider cognition is a prime example of this, with its intricate interplay with silk webs, gaining us insights into the fascinating world of arachnid behavior and the broader principles of cognitive evolution. From the depths of ancient history to the gardens of today, the enduring partnership between spiders and their webs serves as a testament to the remarkable ingenuity of nature and the boundless complexity of the living world.

Are webs part of a spider's mind?

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