Snares are anchored cable nooses set to catch wild animals. There are two types, active and passive. An active snare has the wire under tension and a trigger to cause it to snap closed, while a passive snare has a one way cinch so that as the prey struggles the noose tightens and strangles the prey. Based on admittedly messy and ill sourced numbers, it seems a realistically sized spider could build passive snares to catch and kill medium sized mammals. Also of note, spider silk undergoes Supercontraction when exposed to water so tensioning an active snare might also be possible. So my actual question is, are there any impediments to a spider evolving this ability, what interesting implications might it have for the overall ecosystem?
The admittedly messy and ill sourced numbers:
- Steel snare (capable of catching raccoons and coyotes: 1lb/12 (37.8g)
- Silk to Steel strength by weight ratio: 5
- Silk produced per 23000 4cm spiders per week: 1oz
- Largest spider: 11.9cm / 175 g
This gives 6 weeks, for a real sized spider. Which sounds like a lot, but these traps should be reusable. So the spiders would be capable of killing prey 20 - 100 times their own mass.
If someone finds better sources that lead to different numbers, that would also be great.