Things Better Left Unvisited:
Exactly What It Sounds Like, Mates.
Quick--define "cannibalism".
If you said, "Why, that would be when a member of a species eats another member of the same species, of course, Wise and Powerful Milkshake of the Spider", then you'd be right. You'd also be overestimating my phenomenal cosmic powers. I just write words, I don't grant wishes.
Weeeeeell then, let's just see what the creatures of Redwall, namely the self-purported goodbeast clade, define it as:
Oh. Oh my. Wait, then it has... Hunh?
How is it that this makes sense to anybeast in this universe? Is there a list of cannibalistic and non-cannibalistic actions somewhere in some old tomes in Redwall that everyone has to memorize? Because without that I see no real pattern that determines what they think cannibalism means.
Let me show you. I'll list all the bits I can find from the volumes that I own and you can reference that handy definition you sort of provided above to see if the woodlanders own a dictionary (Here's a hint: THEY DON'T):
It's cannibalism for a common lizard to eat a mouse or mole, but in a later volume it is not considered this when a monitor lizard wishes to eat a vole or mouse.
It's cannibalism for a fox to eat a stoat (or "ermine" as they're called).
It's cannibalism for a stoat (again, "ermine") to eat a fox.
It's cannibalism for a rat to eat a hare, but not for a variety of vermin species to eat a rabbit. But the "rabbit: was actually a hare in that one.
It's cannibalism for an otter to eat a rat. It's also really sick for an otter to rip a rat's throat out with his teeth and then chat animatedly with the victim's corpse. And it's even sicker for the otter's new companions to just quietly keep their horror and disgust at this to themselves:
*Seriously, They Just Let It Slide*
Folgrim the otter still had blood running down his face. Though normally in the woodlanders' society the otter would have gotten a serious wrist-slapping for such a dreadful crime, Trimp just shrugged.
"Er, okay. Just don't bite any more minorities to death while yore with us." she finally consented.
"Yeah," Gonff agreed, grinning in that way that told Martin the Warrior that something really scarily racist was about to pop out, "After all, it was just a rat!"
The mouse warrior slapped a paw to his face before he remembered that he was really vehemently racist too. They all joined hands in a ring, chanting:
"Yaaay! Let's go kill more random vermiiiiiiiiiiiin!"
It's cannibalism for a fox to eat a hare or a rat.
It's cannibalism for an anything to eat a wolverine, apparently.
It's cannibalism for a toad to eat a shrew, badger, or hare. Also a toad eating another toad is implied, but that's never called cannibalism. What in Hellgates is that about?
But then you have raptors, snakes, large eels, pike and other such creatures eating a huge variety of creature: Mice, shrews, otters, weasels, stoats, hedgehogs, rats, ferrets, foxes, toads, lizards, the list goes on. But none of that is cannibalism, it's just taken as a "Yeah, we know. That's an eagle. They're supposed to eat meat."
And though the goodbeasts seem to hate the idea of eating a bird, they don't consider it cannibalism if a vermin creature (or even a vole or otter at one point) eats one.
And there's one reference to a group of foxes expressing that they are fond of eating dormice, the European equivalent to a chipmunk. And nobeast cried cannibalism.
*sigh* Just stick to the REAL definition, shall we?
More may follow. If you like, you may leave an as-of-yet unanswered bit of unusual Redwall yore as a suggestion, but it is more than likely I'll cover the grand majority of oddness and unmentioned unmentionableness.