bumpity bump, this thread is entertaining. what about karma where the "afterlife" is just one life after another....haha crack myself up.
Well, it'd be funnier if you got the terms right...karma doesn't describe the afterlife. You're thinking of reincarnation.
Serious answer about reincarnation...the specifics depend on the religion and the sect (just like in the Abrahamic religions--you can't generalize about what a Muslim believes based on what Christianity teaches, and you can't say what a Catholic believes based on what the Amish practice), but many Eastern religions don't differentiate between animal souls and human souls. It's possible for humans to be reborn as animals and vice versa. The Jains are known for even brushing the ground before them with a broom as they walk, to prevent themselves from accidentally stepping on an insect. They also have extremely strict dietary rules, down to what kind of plants they can eat since small animals and insects are killed in farming.
Even in more widespread beliefs, there tends to be a concept that all life has equal spiritual value. In practice this may not play out, of course. Some traditions are completely vegetarian, and others make exceptions for subsistence hunting. But again, these are huge generalizations...you're talking about billions of people with widespread cultural and religious differences, even the ones who technically practice the same faith.
Personally, I don't believe in an afterlife really--not one that I, RowdyDogs who enjoys arguing on the internet, am going to in the exact same form. I believe there's a part of all living things, a soul for lack of a better word I guess, that existed before we were born and will continue to exist after, but it's not tied to our egos (in the Freudian sense). I think my critters, and all critters, are the same way.
But when I did believe in a more traditional heaven, I was sure my dogs were going there. My mother is very religious and believes the same thing, so I was raised that way. And she's not even really an animal person!