Most definitions of murder hinge on the criminality aspect; stating it as, a premeditated and unlawful killing.
At first I thought it was more of a moral question. To which there’s the famous Mark Twain quote—which seems as good a discourse as any to start with: “[moral sense] is the quality which enables [man] to do wrong. It has no other office… Without it, man could do no wrong.” Or more commonly espoused, “The fact that man knows right from wrong proves his intellectual superiority… the fact that he can do wrong proves his moral inferiority." And I think this effectively touches on what seems to be ubiquitously agreed here, that there has to be some conscious knowledge and agency for an action (killing) to be considered wrong… A moral intention if you will. We can argue about deontological and teleological ethics another time.
But is wrong and unlawful the same? No. There are things that aren’t necessarily considered wrong, but unlawful. And things that could be considered wrong, but not unlawful. But we’ll get back to that.
Another relevant quote from the same essay* is, “among the animals man is the only one that harbors insults and injuries, broods over them, waits till a chance offers, then takes revenge.” (i.e. premeditate)
So in trying to think of spiteful animals I first thought of a cat. Maybe not all, but my cat has certainly harbored spite towards my dog (he eats her food sometimes) and swipes and intimidates at later times without further, timely provocation. But this is likely anthropomorphization on my part. Going back to the same essay, Mark Twain also has an opinion on this, “Cats are loose in their morals, but not consciously so.” So again, to what level can we determine an animal’s intent? Does it premeditate?
Are we sure animals don’t know what they’ve done when breaking rules we’ve set for them?
A dog can seem to know he’s done something wrong, or is it just aggrandized fear at being caught—in association with our demeanor he knows punishment follows? Probably the latter.
So, so far I get the feeling animals can’t premeditate, and don’t consciously intend to do wrong, which seem to be the necessary and sufficient conditions for Murder.
But does not knowing you’re doing wrong suddenly make the action not unlawful? No. It is still a crime to commit crimes even if unknowingly. Not knowing the law does not protect you from prosecution. So but then again, there are no laws an animal can break as we do not hold them to the same standards. Because they cannot intend to do wrong we do not judge them on any basis of law.
Not trying to peddle Mark Twain as the philosophical authority on animals and their morals, but I think I agree with him.
So in long-winded-conclusion, no, animals cannot commit murder.
*The Lowest Animal - Mark Twain