If you’re dead afraid of spiders, this article may increase your level of Arachnophobia and cause you to go completely nuts. So proceed with caution.
You’re not chickening out are you?
Can spiders hear?
Yes, spiders are pretty capable of hearing despite the fact that they have no external ears at all. They can pick up and process sounds from moving objects, claps, wingbeats of predators and can even listen to human speeches from several meters across a room.
No, we know what you’re thinking, but they’re not ghosts!
How spiders can hear?
Spiders are everything from mysterious to terrifying. They are capable of tasting without a tongue, smelling without a nose and scientist are now telling us that they can eavesdrop on conversations without any ears! Talk about really mysterious!
Apparently, spiders are able to listen and pick up sounds with the aid of sensitive structures on their forelegs called trichobothria (singular trichobothrium).
Trichobothria are basically hair-like structures that are fitted into the bottom of a deep, wide cut on the surface of the spider’s forelegs. This cut is filled up with a super flexible membrane which grants the rooted trichobothria some really extraordinary mobility.
This means that they easily set into motion whenever they are subjected to any airborne vibration no matter how small it is.
When humans speak, clap or chairs are moved at reason distance (usually nothing more than 5 meters away from a spider) the trichobothria hair present on the spider’s legs respond by vibrating very fast and thereby producing electrical signals that are sent to the auditory nerve connected to the auditory centre of the brain where the electrical impulses are perceived by the brain as sound. The brain then translates the impulses into sounds that spiders knows and understand.
Can you imagine? The spider even has an auditory nerve for sensing whatever is being said! You really should be very mindful of what things you say around the house! 🙂
The hairs according to research are most sensitive to low frequency sounds within the 80-130Hz range, and this invariably corresponds to the pitch of a very deep male voice, and flap sounds from parasitoid wasps, the main predator of jumping spiders: the spiders that were used for the hearing experiment by the way.
Spiders can perceive sounds from several distance away (upto 5 meters according to the experiment).
What can spiders hear?
By now you know that spiders use hairs on their legs to catch sound waves from several meters away and send them through as electrical impulses to their brains for interpretation, just the way it happens in the human body.
But what exactly do spiders hear from all this? What sounds do their brains translate to from these impulses?
It’s boom boom
It turns out that the overall sensory experience of spiders is actually less rich compared to that of humans.
When someone across a confined room utters the name “mustapha”, the human brain after receiving the sound waves turned electrical impulses from the ear, treats, filters and translates these impulses exactly as the initial uttered word with enough clarity, but in spiders, things happen very differently.
All they are able to hear is a sound similar to what you get from a really bad microphone connection according to Paul Shamble, an arachnologist who lead the spider hearing research at Cornell University.
Their brains are not well developed to be able to interpret sounds exactly the way human brains do. Their brains lack the ability to filter out unnecessary noise and disturbance and so what they interpret as a clap, speech or moving chairs is usually a very dull sound lacking any clarity and meaning whatsoever.
Their ability to hear can perhaps be interpreted in one way, as an adaptation for avoiding predation. In the case of jumping spiders, their predators of parasitoid wasps have wingbeat frequencies that fall within the range that their legs hairs are most sensitive to (80 to 130Hz).
The ability to detect this from several meters away perhaps allows them to go into hiding away from these predators. It’s possible that this is only one of the numerous functions of hearing in spiders, and we may get to discover the rest from future researches.
Previously held misconceptions about hearing in spiders
It was a generally held belief that spiders couldn’t hear sounds. Researches did observe that their tiny flexible trichobothria were super sensitive to airborne vibrations emanating from around their body length and few centimeter away, but that was really the end of the knowledge.
Nobody knew that these deflections were interpreted as neural activity in the brain (meaning that they were translated and heard and not only sensed), and that these deflection could even be induced at distances up to 5 meters away, until a team at Cornell university were able to prove so in 2016.
What was really fascinating about their discovery was the fact that they initially set out to monitor how the brain of spiders processed visual signals and then accidentally ended up discovering the auditory abilities of spiders.
They steered the direction of the research towards that strange discover from there on.
How did researchers come to know that spiders could hear?
While the team at cornell university were busy investigating jumping spiders to see how their brains processed visual information; they bore super tiny holes on the spiders head and insert small micro electrodes to do this, they began noticing that the brains of the spiders were responding when chairs were moved around the lab or when one of the team member clapped their hands.
The response appeared as a “neuron fire” on screen and was heard as a pop sounds from speakers connected to the graphic displaying computers.
When they noticed the response, they began clapping and moving objects around the room while increasing distance to see when the spider would stopped registering the pop. They found this distance to be at approximate 5 meters away.
To figure out exactly how the spider was able to hear them, having already known that spiders have no ears and that their hairs were very good sensory organs, the team placed water droplets on the legs of the spiders to bounce off the sound waves from the claps and chair movements around the room, by about 90% or more.
This was possible because the water droplet greatly restricted the vibration of hair. What they discovered was absolutely stunning. The neural response of the brain disappeared and when the water droplets were removed, the neural response came back.
This satisfactorily indicated to the scientists that the hair on the forelegs of the spider responded to vibrations in the air, similar to how the ears and ear drums in humans and other long-distance hearing animals worked.
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Cite this Article ” (APA Format)
Bunu. M. (2020, May 13). Can spiders hear?. Retrieved from http://emborawild.com/can-spiders-hear/