Some of you will be guffawing to your Objectivist selves saying, "Self, how ridiculous this JCFolsom is! Everyone knows animals have no rights! They think not, they communicate not, they can enter into no agreements. They work by pure instinct, not rationality; they are no different than the robotic toys that imitate them, purely property." Please correct me or add justifications if I'm wrong or understating the case.
Yet, methinks we can demonstrate quite clearly that at least some animals can indeed think, communicate, and even enter into agreements. We shall take as our example that oldest of human allies, the dog. What other animal so clearly feels as a dog? Evident in them is anger, fear, joy, and affection. Those who deny it are committing the opposite error to anthropomorphizing, discounting all human-like features as mere deceptions because that fits more neatly with their pre-conceived worldview. Taking this position, you may as well count all other humans as philosophical zombies, too, and thus justify slavery.
Animals also enter into agreements. Dogs on a show room floor expect and receive treats, above and beyond the food needed to keep them healthy, for performance. That this agreement was not spelled out in words makes it no less real. Humans can and do come to such agreements. If the trainer consistently failed to produce treats for performance, the dog would cease performing in a nearly perfect example of inter-species trade.
Dogs can also solve problems, figuring out how to unlatch gates and the like with the rather dissimilar tools at their disposal. Their ancestors in the wild, wolves, learn via experience the best strategies to capture their prey, and coordinate with other members of their packs to do so as well. I have seen stories of certain types of birds and primates grieved unto death at the loss of a mate or mother, too depressed to eat or otherwise care for themselves. Elephants have been observed blocking the roads of poachers with logs, and caressing the bones of their dead.
Is this complicating for our activities towards animals? You're damned right it is. Nonetheless, I believe the case can be made that any being that acts primarily from its own motivations cannot be truly owned, in that ownership implies primary control. Indeed, methinks this is the only real argument against slavery, including that slavery which a person enters into voluntarily. The one who sells himself into slavery does so fraudulently, whether he realizes it or not.
I'll leave it there, for now. Fire away!