Trying to understand Karma

I know the gist is that whatever energy you put into the universe, you will eventually receive it back, good or bad. I also understand that this can transcend lifetimes. For example, two incarnations ago, you murdered/raped/tortured someone and eventually you’ll pay that karma forward one way or another.But what I don’t understand is that it’s almost certain that at least one time during your existence, your incarnation was a predator animal that relied on killing your food to survive.I understand that if you were a human, you would have the choice to kill. Unless it’s in self defence, humans don’t usually rely on killing to survive. So if we commit murder, we will have to pay our karma forward. That makes sense.But does it work the same way with, for example, a lion chasing down a gazelle? The lion needs that gazelle to live, so I can’t see negative karma making sense if it’s a life or death situation. I don’t understand having to pay back negative karma several lifetimes later because your lion incarnation needed to survive.