Being a crazy biologist, I thought it would be fun to see how hermit crabs react to the availability of an unexpected big Rolls Royce shell. They'd been congregating near the showers, so I put it there. At night there was a seething mass of hermits swapping. Shells are at a premium, and I'd noticed earlier that the smallest one was making do with a discarded toothpaste tube cap. It looked very sad.
Well, the next morning there was no sign of the orgy. No hermit crabs to be seen, no discarded shells, no debris. But in one corner of the shower stall, there was the toothpaste tube cap, no longer needed.