Answer:
"Do rats eat rats?"
Technically, the house rat is a scavenger and mostly thrive on rubbish as well as dead creatures so it is possible for rats to eat other rats especially if they are dead.
One sure answer though, is that a rat can eat even a creature of the same kind or from the same phylum (Rodentia) because a colleague of mine had a hamster who died due to rat bites.
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Also, if two or more rats don't like each other they may try to kill and/or eat each other, and if a female rat who just gave birth is stressed or disturbed while or just after giving birth, she may abandon or kill and eat her babies.