When tragedy befalls an animal, we tend to be more upset about it because animals are innocent. They're not aware like we are and can't make better choices when we can, so when they get caught at the wrong place at the wrong time, it's somehow sadder to a stranger than if it were an adult human.

You see this in cinema. We're relieved that the cat survives in Alien, even though we just watched several humans die horribly. And we kind of feel like John Wick's Roaring Rampage of Revenge is justified after the Russian mafia kills his dog.