The generation of Noach was corrupt. Men would steal the wives of other men. The society became immoral. We learn from this that cattle mated with wild beasts, the dog went after the wolf, the rooster after the pheasant. Animals left their own species to mate with other species.
Animals behave according to instinct.
G-d created dogs to mate with dogs. The behavior of man effects the world at large. When man lives a moral life and does kindness etc. When you raise your values, the world s value s are raised up too. Our actions have global effects.