Well, I searched and found nothing, so here's my question? What in the **** causes a deer to urinate blue?

If you guys want pictures I could probably snap some tomorrow but we own a small food plot that is quite popular with the deer. Now when I walk through the woods/ravines I find many spots where their urine is blue, literally blue. It's kind of half and half with the brown urine as well.

I don't know, maybe it's not an odd thing but it's the first year I've ever noticed it. Dad told me about it first and I thought he was kidding, nope, I found at least a dozen spots out there.