# How Do We Know Tarantulas Have Bad Eyesight?



## CABIV (Jan 18, 2017)

I was thinking about this the other day, and I was curious how we know they can't "see" that well.  

You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly.  Indeed, tarantulas seem to be indifferent to their surroundings. 

Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?

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## ledzeppelin (Jan 18, 2017)

Im no scientist, but there are methods that determine the general sight of animals, which colors they see.. It depends on a number of some receptors and stuff like that.. To answer with a practical example: if they (Ts in particular) had good eyesight, they wouldn't web on the floor so much.. Webbed floor enables them to feel the movement of prey and predators. If their eyesight was good, they would hunt openly, like a praying mantis would, for example.. 

This is just a laypersons answer.. I'm sure many will follow with more scientific content

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## Chris LXXIX (Jan 18, 2017)

Aside for the *Goddess *0.1 _Pelinobius muticus_ PBUH (Peace Be Upon Her). She can see pretty well and granted me the honor to be Her devoted & humble Priest u_u

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## Bugmom (Jan 18, 2017)

CABIV said:


> I was thinking about this the other day, and I was curious how we know they can't "see" that well.
> 
> You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly.  Indeed, tarantulas seem to be indifferent to their surroundings.
> 
> Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?


I don't think they're indifferent to their surroundings in the least, they just "see" their world differently than we do, because their world is what they can feel and probably smell, too. A female tarantula knows a male has come a-callin' because she feels his vibrations from tapping. This is similar to the mating dances with birds - the arachnid equivalent of bright plumage and Riverdance moves. Birds need those displays because birds rely on their eyesight to navigate their world. Tarantulas rely on the vast number of sensitive setae covering their bodies. Although I'm not sure why jumping spiders are as hairy as they are, given their relatively good eyesight, but on the other hand, they're not tarantula levels of hair.

But then you wonder, why are some tarantulas "hairier" than others? Bumba cabocla is hardly "hairy" at all. Does this mean that species has better eyesight than Brachypelma albopilosum?  Heck if I know. Someone answer this!

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## Venom1080 (Jan 18, 2017)

they wait for prey to come to them. if you ever see a tarantula run after a cricket from across the cage let me know! 
seriously though, if youve ever kept wolf spiders, youd see how a spider with good eyesight hunts compared to a tarantula.

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## Devin B (Jan 18, 2017)

I think its because they have a hard time reading the paper unless its fairly large print, or if mine are wearing their glasses (which are really thick).  Also tarantula glasses are really expensive.

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## Ungoliant (Jan 18, 2017)

CABIV said:


> I was thinking about this the other day, and I was curious how we know they can't "see" that well.
> 
> You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly.  Indeed, tarantulas seem to be indifferent to their surroundings.
> 
> Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?


A lot of this information comes from _Biology of Spiders_, and I would encourage you to get a copy of this book if you want to learn more about spider anatomy, physiology, and behavior.

Most spiders don't rely heavily on vision but tactile and chemical cues.  For example, orbweavers can only see differences in light levels, which helps them entrain their circadian rhythms to the day/night cycle.  Their eyes don't form clear images, and they rely mostly on the vibrations transmitted through their webs to know what is going on around them.

Hunting spiders (such as jumping spiders and wolf spiders) tend to have better eyesight, which is usually indicated by the presence of large median eyes.  (Jumping spiders have the best vision of any spider.  Not only do they see in color and have binocular vision for gauging distance, but they can see ultraviolet and polarized light.)

Animal vision is assessed in a variety of ways.  First, you can study the anatomy of the eye.  As noted in _Biology of Spiders_, "the efficiency of any eye is determined by the design of its optics and by the structure of the retina.  Both are well developed in jumping spiders."  Tarantula eyes seem more similar to those of other spiders with less acute vision, although I would not be surprised if arboreal tarantulas like _Avicularia_ that need to navigate trees could see a little better than terrestrial tarantulas that hunt from burrows.

You can observe their behavior in the field.  For example, there is a species of wolf spider that navigates differently on sunny days that on cloudy days, indicating that it is using the sun and/or polarized light.  Jumping spiders continually orient themselves to track prey and other things that catch their attention.

In artificial settings, you can deprive them of certain sensory inputs and see how they behave.  For example, many jumping spiders don't hunt well in darkness or red light (the end of the spectrum they can't see well), whereas a web-dwelling spider can capture prey with or without light.

You can try to test their ability to distinguish between objects, such as objects of different colors.

Placing a mirror in front of a spider can show whether the spider is seeing an image of itself.  (There are lots of cute videos of male jumping spiders making threat displays at "the other male" in the mirror, whereas tarantulas seem indifferent to their reflections.)

You can place 2D images or 3D models of prey or other spiders before the spider and see if it reacts without any tactile cues like motion.

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## ledzeppelin (Jan 18, 2017)

Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?

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## Ungoliant (Jan 18, 2017)

ledzeppelin said:


> Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?


I've wondered that about _Avicularia_ as well.  It may just be a "leap of faith" that they take to escape a desperate situation.  (In their natural habitat, there is a good chance that they will be able to grab onto a leaf or branch on their way down.)

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## Venom1080 (Jan 18, 2017)

ledzeppelin said:


> Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?


if you had the choice of being eaten by a monster or jumping off the hand to a uncertain fate, what would you do?  
its a last resort Avics do to escape predators, not to mention they live in trees and plants wheres theres almost always something beneath them.

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## ledzeppelin (Jan 18, 2017)

Venom1080 said:


> if you had the choice of being eaten by a monster or jumping off the hand to a uncertain fate, what would you do?
> its a last resort Avics do to escape predators, not to mention they live in trees and plants wheres theres almost always something beneath them.


That's true, but I do imagine that arboreals have better eyesight in general.. I think they need it more

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## Venom1080 (Jan 18, 2017)

ledzeppelin said:


> That's true, but I do imagine that arboreals have better eyesight in general.. I think they need it more


ive read stuff that says that, yeah, but ive never really seen any proof.

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## ledzeppelin (Jan 18, 2017)

Venom1080 said:


> ive read stuff that says that, yeah, but ive never really seen any proof.


Yeah.. But I guess due to the fact that there's a severe shortage of tarantula related studies.. which sucks.

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## dopamine (Jan 18, 2017)

Tarantulas are the last spiders in the evolutionary line. True spiders, notably hunting spiders like the jumping species and wolf spider, have developed infinitely better eyesight. Some have even speculated that the Salticidae genus have intelligence not unlike a cat.

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## Venom1080 (Jan 18, 2017)

dopamine said:


> Tarantulas are the last spiders in the evolutionary line. True spiders, notably hunting spiders like the jumping species and wolf spider, have developed infinitely better eyesight. Some have even speculated that the Salticidae genus have intelligence not unlike a cat.


wouldnt that make tham the first in line? and im pretty sure trap door spiders are more primitive. 
if you want to see a intelligent spider, look up the portia spider on youtube. it _plans_ its attacks on other spiders.

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## KezyGLA (Jan 18, 2017)

Joking aside, when I walk into my T room most African sp. will dart for their hides before I can walk into the middle of the room and the big NW terrestrials will retreat when they feel me come into the room 

I may get shot down for this but in my experience I feel I must say a few things. 

The only Theraphosidae I have seen with what may be ' bad eyesight' is Grammys, Aphono, Brachy and Avic.

You can sometimes drop it right on their web right next to them, you think they arent hungry them go to remove but once you intervene with tongs they then know its there?

Over the years, whenever I have dropped prey they will usually put the front legs straight over prey, in what seems like a 'what is this, and can i eat it' effect. 

Yet I am no spider man 

Were whenever I have dropped prey into a baboon sp. enclosure it will disappear as soon as it moves on their web. As if they see it closing in. I have noticed thi with eastern Asian sp. too. It is almost like they watch it before you let go. 

I have been experimenting with a few of the 'thele' species and they seem to not miss anything. You can be in the same spot away from the tank and move slightly then there is a burst of speed that seems to come from nowhere as tbe leg it around the emclosure without you having touch the thing. 

Although I believe that there has got to be genus with bad eyesight out there, i dont think applys for all. 

(Please excuse me it may not sound right, I tried to use google traductor for english)

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## Ungoliant (Jan 18, 2017)

KezyGLA said:


> Joking aside, when I walk into my T room most African sp. will dart for their hides before I can walk into the middle of the room and the big NW terrestrials will retreat when they feel me come into the room


They are extremely sensitive to vibrations, even ones you can't feel.

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## KezyGLA (Jan 18, 2017)

Ungoliant said:


> They are extremely sensitive to vibrations, even ones you can't feel.


I know this but I believe that there are some sp. with much better eyesight than other.

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## dopamine (Jan 18, 2017)

Venom1080 said:


> wouldnt that make tham the first in line?


First in line, my mistake lol

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## viper69 (Jan 21, 2017)

CABIV said:


> I was curious how we know they can't "see" that well.


Scientists have studied their vision decades ago, I believe back in the 60s, certainly the 70s. If you google, you can find some scientific papers in peer-reviewed literature to read. We know what wavelengths of light they are sensitive to as well generally speaking.



Bugmom said:


> I don't think they're indifferent to their surroundings in the least, they just "see" their world differently than we do


Are you speaking of vision? If so, this is not entirely true, their vision is not that great, scientific studies have proven this.



ledzeppelin said:


> They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?


I'm pretty certain there are no published studies of this type for tarantulas, for true spiders such as Jumpers there are! As it's obvious they are visual predators.

Some long time keepers of Ts have speculated based on observation that Pokis might have better eye sight than say a NW Brachy. I've certainly experience things that indicate this. I do not however have proof. What they see however I don't know.

I do "know" that Avics will jump off you without any knowledge of what is around them. You have to remember in the wild they EXPECT their to be branches and other things to break their fall to grab a hold of. They are not expecting to jump off of something, ie one's arm, and have no trees bushes etc around them.

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## viper69 (Jan 21, 2017)

KezyGLA said:


> I have been experimenting with a few of the 'thele' species and they seem to not miss anything. You can be in the same spot away from the tank and move slightly then there is a burst of speed that seems to come from nowhere as tbe leg it around the emclosure without you having touch the thing.


You mean incei? If so, they are particularly sensitive to vibration IME, I don't think its vision at all. They are the only species I own that is SO sensitive to the slightest of vibration.


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## Ungoliant (Jan 21, 2017)

viper69 said:


> You mean incei? If so, they are particularly sensitive to vibration IME, I don't think its vision at all. They are the only species I own that is SO sensitive to the slightest of vibration.


It may be that, being web dwellers, the vibrations are transmitted better through the silk than on substrate alone.

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## KezyGLA (Jan 21, 2017)

viper69 said:


> You mean incei? If so, they are particularly sensitive to vibration IME, I don't think its vision at all. They are the only species I own that is SO sensitive to the slightest of vibration.


When I say 'thele's I mean Dolichothele, Heterothele, Neoholothele and Holothele sorry. Not just N. incei. I should have been more clear. My apologies.


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## viper69 (Jan 22, 2017)

KezyGLA said:


> When I say 'thele's I mean Dolichothele, Heterothele, Neoholothele and Holothele sorry. Not just N. incei. I should have been more clear. My apologies.


Ah I see.


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## YagerManJennsen (Jan 23, 2017)

(This might have been said already; I didn't read the whole thread)
From just a hobbyist POV, I was observing one of my avicularias just last night and you can see just by the way they walk around. Going slow stretching out the front legs in the air and lowering them down; It just looks like they are navigating by touch much like if you were in a dark room and wondered around with your arms waving about trying to get ahold of something.

There's probably better explanations than this, this is just my interpretation.

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## viper69 (Jan 23, 2017)

YagerManJennsen said:


> (This might have been said already; I didn't read the whole thread)
> From just a hobbyist POV, I was observing one of my avicularias just last night and you can see just by the way they walk around. Going slow stretching out the front legs in the air and lowering them down; It just looks like they are navigating by touch much like if you were in a dark room and wondered around with your arms waving about trying to get ahold of something.
> 
> There's probably better explanations than this, this is just my interpretation.


Terrestrials do this as well. There's no scientific debate as what a tarantula's primary modality is, none at all.

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## Matttoadman (Jan 26, 2017)

I have kept my A. seemani in a 2.5 gallon tank with a glass lid(holes drilled for ventilation) since oct. Last night I replaced it with a heavy duty large meshed screen
	

		
			
		

		
	



	

		
			
		

		
	
 to allow it to air out a bit. As soon as I placed it on to she ran up the side and started to chew on it. The question is could she see the lid change or feel the "openness"?


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## viper69 (Jan 27, 2017)

Matttoadman said:


> I have kept my A. seemani in a 2.5 gallon tank with a glass lid(holes drilled for ventilation) since oct. Last night I replaced it with a heavy duty large meshed screen
> 
> 
> 
> ...


Their vision isn't that good at all. It's very basic due to their "eye" anatomy. T likely sensed the air currents from the new lid. You gave your T a worse lid, what a bad idea. You need to switch. People have had Ts lose fangs on screen.

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## Matttoadman (Jan 27, 2017)

Yeah she's went into premolt now. It got damp from water dish war so while she is under I am airing it out. I am going to tape it up soon.


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## smitje (Jan 29, 2017)

viper69 said:


> Their vision isn't that good at all. It's very basic due to their "eye" anatomy. T likely sensed the air currents from the new lid. You gave your T a worse lid, what a bad idea. You need to switch. People have had Ts lose fangs on screen.


Im trying to grasp this a bit. It seems to me that some of my T's sense exactly where the opening of the enclosure is at (I had 3 bolting on me so far, in a controlled environement) 

So if they dont see the exit how does a brainless spider translate vibration into a 3D model of its surroundings? How does it calculate where the hatch is at with me breathing over it and causing all kinds of weird vibrations?


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## viper69 (Jan 29, 2017)

smitje said:


> Im trying to grasp this a bit. It seems to me that some of my T's sense exactly where the opening of the enclosure is at (I had 3 bolting on me so far, in a controlled environement)
> 
> So if they dont see the exit how does a brainless spider translate vibration into a 3D model of its surroundings? How does it calculate where the hatch is at with me breathing over it and causing all kinds of weird vibrations?


They aren't brainless per se, they do have a nervous system. Use google scholar to find articles dealing w/T and true spiders. There's more biological research done on true spiders than Ts.

As for this "How does it calculate where the hatch is at with me breathing over it and causing all kinds of weird vibrations?" You have used too many pronouns for me to understand.


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## smitje (Jan 29, 2017)

viper69 said:


> They aren't brainless per se, they do have a nervous system. Use google scholar to find articles dealing w/T and true spiders. There's more biological research done on true spiders than Ts.
> 
> As for this "How does it calculate where the hatch is at with me breathing over it and causing all kinds of weird vibrations?" You have used too many pronouns for me to understand.


Im sorry for that, english isnt my mother tongue.

What Im trying to understand is how does the spider know where the door is without visually seeing it? If it would sense so by vibration or airflow it must somehow convert these "feelings" into a map making an escape possible (or does it have other means of recognising an exithole)?

Seems like a lot of processing for a spider to me. Especially when I am also there vibrating and breathing. Me as a disturbing factor should impair its senses at least a little but they always seem to get it right, no matter how small the escape hole is.


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## viper69 (Jan 29, 2017)

smitje said:


> What Im trying to understand is how does the spider know where the door is without visually seeing it?


Through touch via trip wires, different vibrations when the door is opened, air currents etc. Read up on sonar/bats. How do they generate a map via sonar?  That may give you a few more things to think about.

Maps are formed by all sorts of modalities, not only vision. Some maps are formed by the detection of magnetic fields.



smitje said:


> If it would sense so by vibration or airflow it must somehow convert these "feelings" into a map


Correct, though whether they get a full map that is remembered, or a partial map that is generated just for that moment, I don't know. I've observed things that make me think they remember certain cues, and other times, not hah.



smitje said:


> Seems like a lot of processing for a spider to me.


Clearly they are able to do it, regardless of what we think. You are clearly underestimating them.



smitje said:


> Me as a disturbing factor should impair its senses at least a little but they always seem to get it right


Clearly you don't


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## Ungoliant (Jan 29, 2017)

smitje said:


> What Im trying to understand is how does the spider know where the door is without visually seeing it? If it would sense so by vibration or airflow it must somehow convert these "feelings" into a map making an escape possible (or does it have other means of recognising an exithole)?


I would expect it to be analogous to how we use our stereo hearing to locate the source of a sound -- except tarantulas have eight legs to help them pinpoint sources of vibration or moving air with amazing precision.


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## smitje (Jan 29, 2017)

viper69 said:


> Through touch via trip wires, different vibrations when the door is opened, air currents etc. Read up on sonar/bats. How do they generate a map via sonar?  That may give you a few more things to think about.
> 
> Maps are formed by all sorts of modalities, not only vision. Some maps are formed by the detection of magnetic fields.
> 
> ...


Haha, very true thats why I am asking. I am keeping 30 T's at the moment, including some "jumpy" ones and never underestimated any of them. I know their love for me is a lot less then the other way arround and I know they are quite capable of ruining my day.

Its purely out of interest "how does a T percieve its environement". I remember a picture I have seen visualising how a fish or some other animal sees the world. Long time ago. I guess there is No such thing for T's as they rely heavily on other senses.

Even sonar and magnetic fields are easily visualised. But my T's, got no clue. If they sense mainly through vibration how do they filter out prey, escape holes and so on in a room cluttered with disturbances? Sonic booms make marine creatures swim ashore and solarflares disorient pigeons. To be honest I havent put a T on a washing machine yet but Im pretty sure they would find the exit.

I guess well never know for sure


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## Garth Vader (Jan 29, 2017)

We as humans are such visual creatures that it's hard to imagine how another creature can know things so well without seeing.  They can sense air and movement in ways we cannot really imagine.  It's pretty amazing.  

I have a dog who was born with a birth defect and his eyes never fully formed. He is completely blind and knows nothing else.  Now dogs see, but they mainly take in information through hearing and smell.  It is incredible to watch him get around.  He seems to make a mental map of an area and hardly ever runs into things. I have watched him sense a tree right before he would plow into it and then darts out of the way. I'm used to it because he's been my dog for years now, but I notice that people tend to be completely flabbergasted by his ability to get around.  He is not helpless at all.  He plays fetch, goes up and down stairs, plays on the beach, etc.  I just imagine people are so struck by him because we as humans really struggle without the sense of sight and we depend on it for almost everything we do.    

Obviously dogs are very different that tarantulas, but this is an example of how animals can observe their environment with other senses.

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## smitje (Jan 30, 2017)

Im getting that. Pretty amazing stuff indeed. Makes me wonder how far they can venture out before loosing their way.


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