The bat droppings will be in several piles if you have an infestion of bats.
Bats tend to stay in dark areas such as caves and attics. If you suspect bats in your home you will need to check the attic and look in the crevices where the wall meets with the rafters. Bats do not gnaw at property like rodents do. They can, however, get in through openings made by these rodents. They will leave stains on the walls that are from the oils of their skin and will remain quiet unless disturbed. Droppings are another way you can tell if you have an infestation of bats. There is a distinction from bat droppings to dropping from other pests that may enter the home.
Look at the shape of the droppings. Bat droppings will be long and segmented. They are not round or oval and do not harden like droppings from other pests such as rats.
Crush the droppings. Bat droppings are powdery when crushed and are extremely easy to crush. They are friable and can easily fall apart sometimes without trying to crush them.
Check through the droppings. There should be small pieces of undigested insects within bat droppings.
Notice if the droppings are in one pile. Typically, the bat will drop fecal matter below where it hangs or sits.