Spiders are one creature that sparks both disgust and fascination; their hairy, leggy bodies and hunting habits turn most people off, but their incredible Spidey-skills cannot be ignored.
Spiders are prolific predators and should be a welcome visitor in your home. Their ability to trap and kill large numbers of insect prey can help to keep your house clean and bug-free (albeit a little webby in places). The tiny spider has a whole arsenal of skills that make them effective hunters, but how do they evade predation themselves? Do they really have special senses to help them detect and avoid danger and, if so, how do they use them?
How do spiders sense danger?
Spiders use their eyes to detect danger
It may seem anticlimactic, but the spider’s first danger-seeking sense is good, old-fashioned sight. Just like you and me, spiders come equipped with eyes; four pairs of them, in fact. The sophistication of these eyes (and, therefore, the eyesight of the spider) varies significantly from species to species. However, spiders can generally see well enough to spot and evade an approaching threat.
Spiders can ‘hear’ using their body hair
Arachnids are generally disliked for their hairy appearance, but those hairs play a vital role in the way spiders sense danger in their surroundings. These tiny hairs usually cover the legs and body of the bug and are extraordinarily sensitive, allowing the spider to pick up airborne vibrations caused by sounds up to 3 m away. By doing so, spiders are able to ‘hear’ what is going on around them, a sense that they were previously thought not to have.
A study of sound detection in jumping spiders found that this skill of theirs is quite sophisticated. The arachnids can not only detect different frequencies of sound, but they can even tailor their response accordingly. For example, a low-frequency sound (around 80Hz) will often be interpreted as a possible nearby predator, for example, a predatory wasp. When this happens, the spider usually will stay perfectly still to avoid attracting attention, thus sensing and averting nearby dangers.
Spiders can use their webs to sense danger (and prey)
The spider’s web is, in many ways, an extension of its own body. By sensing and interpreting vibrations along each of the finely spun, silken strands, the spider is able to detect intruders in its web before it even sees them.
Spiders mostly use this talent to locate and catch their prey, swooping in on flies and other insects that get themselves entangled in the sticky strands. Resting with one leg on each strand, the spider plucks at the threads to generate vibrations, which travel throughout the web. If these vibrations hit against an object, the spider feels it in its legs and feet and knows exactly where to go to find its prey. Even more importantly, the frequency of the vibrations tells the spider exactly what type of critter – fly, bee, small gecko – it will have to deal with. This gives the spider the upper hand when approaching potentially dangerous prey.
Though spiders mostly use their webs as a tool for catching dinner, they may also have a hand in helping them evade threats. Their skills for sending out and interpreting vibrations allows them to detect damage to the web, which must be repaired immediately if the spider is to survive. Web vibrations can also give spiders an early warning of approaching danger, giving them a few extra seconds to make a quick exit if they need to.
Other spider superpowers
Spider superpowers were first brought to public awareness by Peter Parker’s wall-scaling, web-spinning alter-ego back in the sixties. Their ability to defy gravity and move with astonishing speed and agility has been well-established, but do spiders have any other superpowers that they’re not sharing with us?
Certain spider species have talents that even Marvel’s best-loved superhero can’t compete with, for example:
The orb spider builds decoy models of itself
It’s possibly the smartest defensive tactic on this list; some spider species, such as the orb spider, actually build body doubles of themselves to evade predators. These dummy spiders, often constructed from dead bugs and bound together with silk, are strategically placed around the web to create the illusion of multiple spiders. Predatory wasps, a common threat to the orb spider, can’t tell the difference between these and the real deal, and will often become confused and attack the ‘model’ spider instead.
The diving bell spider lives almost entirely underwater
The diving bell spider is the only known arachnid species that spends its entire life underwater, despite not having gills. This particular species mates, rests, hunts and breeds under the surface of the water – but how does it survive without an air supply?
The secret is in the ingenious construction of the web, a ‘diving bell’ that is built between fronds of aquatic plants and then inflated with an air supply.
Using this, the spider can store oxygen underwater and only needs to surface occasionally to restock the air bubble.
Spiders certainly have a wide array of special talents to help them hunt and survive, but how do they avoid danger? Pop culture would have us believe that every arachnid is equipped with extraordinary sensory skills; unfortunately, the reality is slightly more commonplace. As it turns out, spiders mostly detect approaching danger using their four pairs of eyes. Although eyesight varies between species, most spiders are able to rely on sight alone to avoid predators. Those with poor vision supplement this sense with a few other special abilities that are, in fact, unique to spiders.
Arachnids are masters of vibration interpretation and regularly use their webs to expand their awareness of their surroundings. The pattern of vibrations that reaches the spider through the silk strands that make up its home can inform it exactly what is in its web, and how to approach it. Some spiders can even use the tiny hairs that cover their bodies to pick up on airborne vibrations caused by nearby sounds. In doing so, they can tell when there is a potential threat nearby and take the appropriate action to avoid it.