We don't know intelligent beings that aren't mammals, either, but that doesn't imply that one is a prerequisite for the other. One could reasonably argue that self-directed agencies are an outcome of the evolutionary process, and predate evolution of intelligence, so the latter necessarily comes with those strings attached in nature. But we're past the "in nature" part by now.

I know that in my mental model of what intelligence is, a completely passive entity that responds to my questions in a certain way would qualify.