I've grown successful dahlias for the first time this year! They are GORGEOUS and my husband I are really enjoying them. I planted them in large pots so they can be brought in in the winter. The problem is, though, that for the last couple of days, I've seen brown droppings on the steps, leaves and new blooms that, frankly, look like mouse droppings. ICK! I can't imagine it IS a mouse, as the plants are four feet high and I would think the stems would break if a mouse was atop them. Not te mention, the compost is not too far away and they would surely enjoy that more!
What can this be??? I can only imagine it's a pest that will ruin my pretty wonders, but I don't know what. I would rather be prepared for the coming fall out, or better yet, be prepared to protect the plants!

Thanks, all! A dahlia photo from yesterday enclosed. :)