City-Dwelling Spiders Build Webs That Don't Work

In welcome news for urban arachnophobes everywhere, it turns out that certain types of spiders just aren't cut out for city life. Apparently, spinning webs on concrete and steel kills the vibrations spiders need to sense prey—meaning dinner ain't coming easy.

In order to see how man-made structures affected spiders' abilities to catch prey, a research team at UC Berkeley hunted for spider webs around campus, noting both the materials the webs were built on and how well they conducted ambient noise. They were then able to replicate each material's level of noise vibration in the lab, even simulating the effect of potential prey with a second web vibrator.

What they found actually surprised them: spiders had the easiest time detecting prey when the background vibrations came mostly from wind. Scientists speculate it may be that the increased activity puts spiders on high alert.

City-Dwelling Spiders Build Webs That Don't Work

They also learned that artificial bases were the quietest, which, interestingly, makes it much harder for spiders to sense intruders. Because while webs spun on the extra-quiet concrete might lower levels of wind vibration, it also lowers the vibrations from any other disturbance.

In other words, spiders that build webs in cities are screwing themselves over twice. Because man-made materials dampen vibrations, the constant buzz of city life means that spiders' webs are almost always vibrating at least somewhat somewhat—even when there's no potential meal on board. Add this incessant hum to the fact that the webs themselves have problems picking up more subtle movement, and you've got a major issue (and a hungry spider).

And sure, spiders may be an occasional nuisance, but as more and more manmade structures start popping up, we risk severely lowering the population or even (in a worst case scenario) wiping them out entirely. And this is just one little species; there are thousands of animal species living in cities that are being affected in ways we have yet to even acknowledge. And if we want to coexist peacefully, we're going to need to figure out how to take the needs of those we displace into account. [Animal Behaviour via Science News]

Image: Shutterstock/krisgillam