You could write it with something like this:
[[6, "rabbit"], [9, "sheep"], [10, "pig"], [11, "cow"], [12, "wolf"]]
Then when you generate your random number between 1-12, you iterate through the array until you find a number greater than or equal to the number generated. This would come in handy if you were rolling a hundred-sided die, but for 12 sides, I’d say your solution is plenty good enough. You might want to at least factor out those object literals into variables though.