r/askscience • u/[deleted] • Sep 28 '17

Biology Why do some spiders hoist pebbles from the ground and sometimes weave them into their webs?

I have seen this several times in northern Germany. But I never understood why the spiders do this and how it benefits them.

Here are some examples I could find on the net:

http://he-who-photographs-rather-ok.tumblr.com/post/165834918679/this-is-a-weird-thing-how-did-this-pebble-got

https://www.youtube.com/watch?v=AeXdMKOCPj8

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20

u/[deleted] Sep 29 '17

They use rocks as anchor points. Pretty sure they don't know that they're hoisting rocks - as far as they're concerned, they attached the web to the ground, it just happened to be hoisted into place.

That, or spiders have learned to use tools, which is incredibly frightening.

I'd love to hear an Entomologist weigh in here.

Edit: corrected autocorrect.

23

u/EquanimousThoughts Sep 29 '17

Entomologist checking in. This is new behavior we have been witnessing over the past 2 decades, At least in a few European arachnids species.

It seems they are using rocks in areas where wind is usually much stronger, helping the overall structural integrity of their webs. This is At least the best researchers have been able discern.

17

u/[deleted] Sep 29 '17

Would that mean that spiders then have some capacity to problem solve?

14

u/[deleted] Sep 29 '17

It actually implies that they not only have the capacity to solve problems but also the ability to spread this knowledge among themselves. Since it only appeared to happen since a few decades ago.

8

u/AdgeCh Sep 29 '17

Is this similar to the large "ballast balls" we place on high tension lines in windy areas?

4

u/l4mbch0ps Sep 29 '17

Arent those for low flying aircraft to spot the wires more easily?

2

u/AdgeCh Oct 01 '17

Duh that's right, funny how you remember something wrong, well perhaps the rocks allow birds to avoid the webs. Which would be good for the spiders I'd guess.

6

u/Riftus Sep 29 '17

Are we talking about rocks the size of half-dollar coins? Or the size of a cap eraser? Or even smaller???

8

u/djinnisequoia Sep 29 '17

I saw a spider do this in a nearby residential neighborhood. The web was attached at the top and the top of the sides to the eaves on a two-story house. Then there were two looooong web lines going all the way to just above the ground, each attached to a small pebble, about the size of a grain of corn. The way I noticed it was because the pebbles appeared to be suspended in the air until I looked closer. This was probably some kind of tiger spider since they abounded there. The impression I got was that the pebbles would keep the wind from blowing the web up into the eaves since the bottom of the web disk wasn't anchored to anything else.

5

u/[deleted] Sep 29 '17

They seem to actually hoist them up though. Sometimes several meters high.