Could have been a hog or a horse. I've always heard that lead has a sweet taste is why animals like to chew it.
I also have some bullets that look like they have human teeth marks. We have all heard the story of pain bullets but I find it hard to believe simply because you never read of it in any of the journals. Not saying it didn't happen, but some will argue that it didn't. I would love to know for sure because some I have look just like human teeth.
I'm no expert by any means, but if it were chewed by a hog, wouldn't it be marred all over. Looks to me like something had to hold it to chew the end like that.. Just saying.