Ever growing list of Horror films with animals as the main character. As a biologist, I tried to order it systematically. Didn't include horror movies with human-beast creatures ...yet (fuck it, I already included several humanoid-beast films).
Also added some non-horror movies with killer animals, like Moby Dick or King Kong.
I will not include any movie with animals of extraterrestrial origin (e.g. mutant alien spiders), but I did included movies with animals from another dimension, because they may be from our world but in an alternative Universe.