Hello, SleepyHead.

Dogs bark at open spaces in films because we perceive them as guardians. They spot danger and warn us of it since about 100,000 years back in our common evolution.

Killing dogs in movies is part of the horror movie makers' nasty "tricks." Humans are emotionally very close to dogs, we are conditioned to especially respond to their yelps of pain like no other creature. Not only we shaped the wolf, but in turn the dog shaped us. Horror movie makers play on that bond when they do cruelty to dogs because we respond so strongly to it, emotionally.

You can compare this with the movie "Equilibrium". Humans take drugs to no longer feel emotions. There's a scene where the thought police kill a group of dogs that were illegally kept as pets. You only hear the yelps.The intention of the movie maker was to elicit a strong emotional response. I frankly couldn't watch after seeing this scene. Same with the first "The Butterfly Effect".

Try to name the Hollywood movie productions where you actually see violence being done to a dog. Contrast this with the intended audience, the mass appeal of a movie. You would see some interesting correlations. Blockbusters almost never seem to directly portray violence to dogs. Contrast for example "Alien" with "Alien III". John Hurt had his chestburster moment in plain view. The alien in "Alien III" comes from a dog, and the camera pans away before the moment. I find the latter one much more depressing, now that I think back to it...

Contrast this with one of the key scenes of "Independence Day". When the aliens blast up L.A. Emmerich makes a point of not only saving Will Smith's movie family but also their dog (in one dramatic leap). This elicits a positive response in turn.

As for the cats - everything that CF said. They just have a reputation of being mysterious, maybe also psychic, and also the witch archetype is still strong in modern storytelling. One of the commonly used pictures is to pair up a mysterious woman and a cat - the archetype in action.