I would recommend leaving something for the unidentified animals to munch on. Place in on a roll of lining paper, or similar, and then inspect any poo left behind. Rat and mouse poo are very different. Mouse poo is as small as grains of rice, rat poo is much larger.
You may have a squirrel though. You will need to google their poo (not something I have ever typed before...).
You may have a squirrel though. You will need to google their poo (not something I have ever typed before...).