* Size: How big is the animal? Is it smaller than a mouse, about the size of a rat, or bigger?
* Appearance: What color is it? Does it have a long tail, a short tail, or no tail at all? Does it have a bushy tail? Does it have any distinct markings, like stripes or spots?
* Behavior: What is the animal doing in your yard? Is it running around, digging, or climbing? Have you seen it during the day or night?
* Location: Where in Maine do you live? This will help me narrow down the possibilities.
Once I have this information, I can give you a better idea of what kind of rodent-like animal you might be seeing.