What rights do non-human animals have that they would still have if humans had never existed? What rights exist among, and are granted, upheld, denied, or revoked by, non-human animals?
They don't appear to have any right to life, amongst themselves.
They don't appear to have a right to freedom of assembly for the purpose of peaceful protest.
They don't appear to have the right to abortion, nor can an abortion be granted or denied or even obtained.
They don't appear to have the right to humane termination, without suffering. (In fact, I've seen video of animals that are still alive and conscious while being consumed by other animals.)
They don't appear to have any right to equal protection under the law. Nor the right to an attorney, nor to have their rights read to them at time of arrest.
I'm pretty sure you know the answer to all of those questions: animals cannot exercise a right to an attorney, assembly, or anything else because the lack the rational capacities to do so. They're no better or worse off than non-rational humans who lack the capacity to exercise any of those rights.
If the argument is "animals don't exercise rights, therefore they don't have any", well then you must deny the rights non-rational humans
for the exact same reason. The argument which excludes animal rights applies to mentally similar humans. Neither of them are moral agents.
Most people don't like that conclusion, because mentally similar humans have some important and interesting capacities, like a capacity to experience suffering and satisfaction. If someone believes that suffer and satisfaction bears moral weight, then
that particular capacity is morally relevant in non-rational humans. It seems clear then, we can respect a person's capacity to experience suffering and satisfaction
even when that person isn't a moral agent. This argument is logically inclusive to animals, so we're obliged to treat them with the same respect.
In other words, moral agency isn't a prerequisite for moral consideration. You'd be hard-pressed to explain why non-rational humans deserve moral consideration, but non-rational animals do not.
Thus, I must again ask: what rights do non-human animals have, that haven't first been granted (or denied) by humans?
In case it isn't apparent, I am advocating that humans are appropriate for determining and upholding animal rights, as humans are the only ones who determine and uphold them, and always have been.
Fair enough. Humans are moral agent and can discover rules relevant to the ethical treatment of humans. Seems uncontroversial enough.
Of course, a more interesting question here is why those rules relevant to the ethical treatment of humans stop at the level of humans. Sure you can say that "humans make the rules", but that's not the end of the story: any given rule has some underlying moral principle. Not everyone agrees on the same set of principles, not everyone agrees that all principles are as good as others, not all principles are logically consistent.
If you've ever been involved in a discussion on homosexuality, you have discussions of this sort all the time. Some guy objecting to homosexuality might say its "unnatural", so his underlying moral principle is that unnatural things are morally wrong -- its easy enough to settle on a definition of "unnatural", such as being manmade or not found in nature, and show that the person accepts many unnatural things as perfectly acceptable, like skyscrapers (manmade), or show that the "unnatural" thing is found in nature, like homosexuality in many species of animals. If you can do that much, you've shown that the general principle underlying the objection to homosexuality is short-sighted, inconsistent, irrational, or just plain bad.
Now, I have discussions of this sort whenever I talk to people about animal rights. Initially, before jumping on the vegan train, I was very much against animal rights but did not like the arguments being used against it. In pretty much all cases, the arguments invoke some obvious fallacy or leave a hole open which logically excludes non-rational humans.
(Case in point: If you've been on this forum or the Internet Infidels forum long enough, you've seen fundies argue that evolution implies social darwinism, atheists shoot it down by saying "survival of the fittest is descriptive, not prescriptive"; in a discussion of animal rights,
the very same atheists argue in favor of eating animals because, well, we're animals, survival of the fittest and all that jazz.)
You can see why that's problematic, right? Even if humans make the rules, the principles that they have are inclusive to non-human animals anyway. Arguments against animal rights have nasty consequences such as excluding a whole class of humans, justifying might makes right, legitimizing racism, resulting in consequences that almost everyone finds repugnant.
Animal rights and human rights aren't different things, they aren't even complimentary, they're the exact same thing. Animal rights are simply a logical extension of the moral and principles that everyone already accepts regarding the ethical treatment of humans.