Although bat droppings look almost the exact same as mouse droppings, one can tell the two apart by comparing consistency, shininess and location. The biggest difference between the two is their consistency, as mouse droppings are hard, whereas bat droppings are dry and crumble when touched.
Another factor that may help identify whether the droppings are from a bat or mouse is their shiny or speckled appearance. Bats primarily eat insects, and the insect wings give the bat guano a distinctive shiny appearance. In addition, bat droppings are normally clustered in one small area, whereas mouse droppings are usually scattered all over the place. If piles of droppings are found in the attic or outside the home, it is likely that they are bat guano. The piles are likely to be located only in those two places because bats only defecate in certain areas, typically before they enter the home and directly below wherever they roost during the day.
Take caution when dealing with potential bat droppings, as they are known to contain a type of fungus that can lead to histoplasmosis. For this reason, it is important never to touch the droppings with bare skin and also to wear a HEPA filter or respirator when cleaning up the droppings.