One might consider the number of arguably intelligent species alive right now on this planet. Humans, two types of chimpanzees, gorillas, orangutans, cetaceans of several types, African grey parrots, corvids, canids, and so on. Clearly, to style any of these creatures, other than ourselves, as "intelligent" is controversial, but this illustrates the point that we share a planet with numerous species which very well may be intelligent, but we can't conclusively establish whether they are or not. Where is a Turing test for dolphins? It is possible we might someday encounter a space-faring race with which we could not communicate at all? Where would they fit in our scheme? Lobsters?