Yeah they might not kill for fun, but there are many cases in which wild animals have killed wantonly and with no intent to consume their kills. It's called instinct, something triggers them, and they kill as many times as opportunity presents itself. The idea that wild animals kill "only enough to eat" is very far from true. Usually the behavior we see, in which animals kill only enough to eat, they are motivated by hunger, they kill, they feed, and are no longer hungry, and because they are no longer in the presence of prey, they don't kill any more. This is because the location of the prey was not what they considered a safe location to consume it, or because while adressing their pressing hunger, the other prey species moved away. Some people try to paint the picture that if you put 20 chickens in a pen with a fox, you could come back in ten days and he would have around ten left. This is not true. He would kill them all the first night.
You can make 1/4 inch grid wire as taught as you like, but because it is a tiny gauge, an animal can go through it in seconds. Much better off with 1 inch grid with much larger gauge wire, or 1" x 1/2" grid, with gauges of at least 16 if not 14.