Dude! You're channeling my 9th grade Biology teacher!

But you're right....something to do with teeth....
Yeah, I have a couple of degrees in Wildlife Science; I should know that one. Rodents only have one set of teeth in front kind of like ). Lagomorphs have a second set directly behind the front teeth kind of like ').
As to eating whatever it takes to survive, it's all about how hungry you are and what is available.