Then they said, "What shall be the trespass-offering which we shall return to him?" They said, "Five golden tumors, and five golden mice, [according to] the number of the lords of the Philistines; for one plague was on you all, and on your lords.
Whether or not the Philistines associated the rats with the tumors or not, the rats (mice) were a devastating plague in themselves, as indicated by the remark of the priests and diviners  (1 Samuel 6:5) that they "ravage the land."  "Aristotle relates that in harvest entire crops were sometimes destroyed by the ravages of field-mice in a single night."[4]