Are these fecal remnants? They don't look exactly like other pics but at the same time are very suspicious.
This is the underside of my box springs. Three separate slats, far from one another, had marks like this. They sort of smeared when I wiped at them in a dusty dark smear type of way.
Thank you.
20160619_181230 by t s, on Flickr
20160619_181015 by t s, on Flickr
20160619_172655 by t s, on Flickr