You are entitled to your opinion on whether animals/snakes have souls or not. Since it cannot be proven to exist, it's always going to be just an opinion however.
People that believe that animals have souls exactly like a human tend to drift down the road to the "animals should have the same rights as humans" road evenually though. Not everyone does.. but it's a tendancy I've seen.
So then you have to decide.. do animals have lesser souls? Is it possible to have a lesser soul? Is a lesser soul less able to be a "person"?
All of the above is moot to me, I'm not certain people have souls, less certain animals would be burdened with such. First, you'd have to define "soul" and it's purpose.