What is this on my bp?

I was checking on all the snakes a min ago. This guy had used the bathroom so got him out and cleaned it up. Was checking him over and I saw this down his side? It looks almost like dirt to me. I tried rubbing it off, but nothing comes off. I have no clue. I just got him a week ago.
https://ball-pythons.net/gallery/fil...0406192049.jpg

It looks like substrate to me...or poop

Yea I was thinking maybe he got in the poop some. He is on aspen bedding. I'll try to see if a wet paper towel will get it off.

I was thinking substrate staining as well, maybe from the prior owner's care?

Ok, that's definitely not aspen, hahaha. So I'm guessing poop. A warm damp cloth should do the trick.

The "dirt" is between the scales, so I think it's just hard to wipe off, as whatever you use skims over the scales without getting all the way into the "crevices".
And in a warm cage, I'm sure it got dried on. ;)

Yea tried getting it off. Won't come off. He's all white. So that's bugging me it being so noticeable haha.

Same reason I don't have white carpeting...:D Might have to wait for him to shed?

BTW, I believe the technical term for this is "schmutz".