Considering the vast number of non-human animals compared to humans, the probability of being a human is vanishingly low. Therefore, chances are that if I could be an animal, I would be.

I do not really think you need an anthropic argument to prove that "you" couldn't be an animal; it is more a matter of definition, i.e. by definition you are not an animal. For example, there is no anthropic reason that "I" couldn't have been raised in Alabama, but what would it even mean to say that I could have been raised in Alabama? That somebody with the same exact genes and parents was raised in Alabama? In that case, it is the same as saying I have an identical twin that was raised there. The fact of the matter is that when I say "I", I am referring to someone with all of the same genes and experiences I have. To say that "I" could have been some other human is nonsensical; to say that "I" could have been a bat is even more so.