You knew it had to come to this: some people in Austria are trying to have a chimpanzee legally declared a "person." In this case, it is not because they actually think the chimp, Hiasl, is a person; rather, to get around a quirky legal technicality in Austrian law.
Are chimps people? No. If we were to assume they were, then all sorts of other problems would arise. For example, could they be charged with a crime? Could they own property? Should chimps be afforded legal protection? Absolutely. I find it hard to argue that a sentient animal is just a "dumb" animal.
Higher mammals have been demonstrated to have many traits that are exhibited by humans (arguably, the most intelligent animal of the lot). These include:
*Compassion (demonstrated by certain large cats bringing food to injured cats in their group)
*Intelligent use of tools (we all know about the chimpanzees who modify branches to make sticks for fishing out termites)
*Ability to communicate in a structured manner we recognize as language (many examples, but the most famous being Washoe, the chimp)
*Organized warfare (sadly, too many examples, including chimps)
*Ability to have sex for pleasure, rather than just reproduction (dolphins)
This makes them intelligent, but it does not make them "persons."
More on the Austrian case will be found in this article.