Animals are aware of God’s existence on some level. The argument for that is that unlike humans, beasts are innocent and do not deserve the sort of separation from God that many humans suffer from. But they do not pray to Him or talk to Him or know Him or love Him as friends. Pigs are not God’s friends.
That is the reason why God would never have created them unless they could serve humans in various capacities who are able to enter, through charity, into friendship with God.
God does not need a merely natural world, with each creature self-sufficient and self-interested and on its own. He wants a single uni-verse united by love. And only rational beings — God, angels, and humans — are able to love.
Now some animals, like cats and dogs, can be uplifted into a kind of friendship with man. Through that friendship they become connected to the vine and branches, and their souls can be preserved by a special act of God upon human request. If a man wants his dog to go to heaven, God, by loving the owner, can grant the wish. I do not find that at all implausible: it is love that saves, and only it.
Generally, however, animal souls are corruptible and are of no concern to anyone.