First, the presence of language and consciousness in a creature simply does not prove self-awareness. Every living thing has some level of consciousness, even plants, and communication is necessary in many (if not all) species of animals, so the higher ones would certainly develop complex methods to do so, including of the vocal variety.
That aside, I believe that I mentioned that sentience may be possible in some animals, like whales, dolphins (basically dolphins are whales more interested in holding still for testing), and many other higher animals. Hell, I'm willing to say (and have, in
print) that
ant colonies could be sentient beings, when considering each ant as an independent brain cell. There are most likely other self-aware folks on this earth, but my point was that they are
not our pets.
That said, if a species
were self-aware, you'd think that by now they would have chosen to tell us about it -- which would have been most helpful for the whales (and gorillas, and elephants, etc, etc) if they shared that info, wouldn't it? Perhaps we would have been nicer to them?
I had no idea that language in animals other than us had been proven, and aside from asking who's proven it, given that scientists have little interest in the subject, why does that matter? Language is a complex method of communication, yes, but are those birds' or dolphins' complex songs filled with metaphor, introspection, hope, fiction, individuality, verse, and all the other things that elevate communication from a simple transfer of information (ie, "I'm over here," or "there is food") to a tool for questioning, establishing, and sharing the nature of our very existence? Don't get me wrong, complex communication --
language -- is an impressive thing for some animals to be doing, but it does not necessarily imply sentience.
In truth I might, because I tell myself that at least once a week; it keeps me honest. Seriously, though, if someone were to tell
me that, I would ask them why they thought it to be true, and perhaps, as I've done many times, have an interesting conversation about the source of the "BS." Are you saying that I should agree with folks who believe that their dog can LD simply because
they believe it can do so? That doesn't seem very fair to me, or to a person who might hold a belief that could need a slight dose of reality injected. Remember, we're not talking about a person's spiritual beliefs here; we're talking about their pets' night life.