I found a box turtle's upper shell in the woods next to my yard. It was so old that all the scales had already fallen off and it was just the white colored shell bone itself. I thought it had potential as a decoration in my garden, so I bought it home, cleaned it up, and set it out to dry.
Next day, the shell is gone. I figured something like a raccoon might have picked it up and carried it away, so I went looking, and sure enough it was laying right up at the edge of the woods. I noticed it looked like it had some chew marks on it, but I figured I had just missed them when I was cleaning. Anyway, took the shell back home again, set it out. A day or two later, it was gone again. Rinse and repeat for a week or so.
Then one early morning I stepped outside first thing and saw a squirrel sitting at the edge of the woods gnawing on the turtle shell. And that's when I found out that squirrels also eat bones of dead animals. From my understanding based on random internet searches, it's usually pregnant females who are seeking supplemental calcium.
