Moral relativism has led us to debate for 24 pages (and counting) whether or not a human life is more valuable than a dog's life. How sad.
That's because there's no answer to that question. It depends on the human and it depends on the dog.
Smoo has hit things right on the nail today.1) Humans are animals. We happen to be the most advanced animal on earth but we are animals none-the-less. Personally, I think we are perfectly right to assert ourselves as such, and to utilize the world as we see fit. But you're kidding yourself if you don't understand that you are still an animal.
2) The save your child or 100 other children parallel is a good example. Some of you have already said you would save your child. I think most people would. However, you would also agree that in general one child is no more valuable than another. To another person, your child would be just like the other 100. But you're making a decision to save your child because to you the parent, that child has much more value than any other, even the sum total of 100 children. Same thing goes with the dog. To almost anyone, a human life is more important than a dog life. A human is more advanced, more intelligent, more capable of doing a number of things. I don't think it's a reach to say that a human has capacity for a more "meaningful" life, whatever you choose that to mean.
BUT......to the dog's master, the dog has more value than somebody else would consider. For the 40-something % of us that answered the way we did, the dog has more value to us than a random person we do not know. It is the exact same equation as the child vs. 100 other kids scenario, just with different weights and variables.