Sometimes we gather things straight out of nature, or somehow come across something that was. I have antlers, feathers, dried lotus pods and a pine cone. Some people use them as curios -- which can be bones of animals long passed when they were found, among other things. I'm of a mind that certain things that like carry the spirits of the creatures they came from. It isn't always that way, I don't think -- but certainly there are times when I've heard strange things around others' altars.
I think sometimes if you are meant to find a curio from a specific creature with a guiding spirit still attached, then you must find a way to keep it with you. Maybe take the time to listen or understand why the spirit is contacting you. It may be linked to something personal for you -- it could be a physical representation of a past omen, or a power animal, spirit guide or animal totem. You never know.
But one thing I have been aware of for a while is that if you are meant to hear the spirits of things, then it is absolutely something to pay attention to. Not that we all know the answers as to why -- but nothing is coincidental. So keep an eye out and an ear open -- you never know what you'll find.