Old dog leaving calling cards

I had a Great Dane years ago that started leaving "calling cards"--I'm sure a bit larger than your Pogo's :-) ! He'd be walking through the house and never knew he did it. After a thorough check-up at the vet, they came up with a problem in his spine. No pain (thank goodness) but no feeling.

I just quietly picked up after him (fortunately they were always quite solid), hoping he didn't notice and feel bad.