Along the way, they encounter three adults who've been dodging the beasts' advances on their mortality for quite some time. As they all try to survive the night, emotional moments are exchanged, secrets are revealed, and surprises that could be not so surprising drive the story towards a rather solemn and open ended conclusion.
Animal feels like the foundation for something bigger. There are clues throughout the film that allow your imagination to run with possibilities but ends with no further exploration into the why's and how's, which is not always a bad idea. A bit more insight without over explaining would've been fine and felt more satisfying. Do not be surprised if we see a sequel.
In short, Animal was about survival, both primal and emotional and the struggle to maintain both. It proposed that they are equally needed to preserve our humanity. Without, the characters were no different than what was hunting them.