Do zombies eat animals or are they just after humans? Some movies, they're only eating people, other movies, for instance, 'Night of the Living Dead', the original modern zombie movie, they eat everything; they eat bugs off trees. They eat anything they can get their hands on that's alive. Many movies and books show examples of zombies moving through an area like a locust, just eating everything alive and leaving nothing left for the survivors that are out there.
This is an easy thing to test. We think that zombies don't work together, so it's not like I'm a zombie and you're a zombie, and we go up to a house and I say, "Hey. I'm going to go around the back and you moan at the front porch. They'll coming running out the back, I'll trip them, and we can both eat them." Zombies don't work together. All you have to do is go outside by yourself without a net, without any equipment, and try to catch a squirrel or try to catch a dog that doesn't want to be caught. The notion that zombies are going to be able to move through an area and just eat every living thing doesn't really seem told hold water. The reason you hunt deer with a rifle is because they don't just stand there and let you walk up to them and bite them.
If zombies do eat animals, it could have a potential catastrophic effect on our own food supply. As we become . . . as civilization collapses and we become much more . . . we go much more back to our hunter/gatherer roots, we need to have something to hunt to be able to hunt, at all. If zombies do eat animals, it could cause severe problems for us, but the zombies have to be able to catch. The animals and the animals that don't want to be caught are generally hard to catch.