Let's stick to the subject. "Intelligence" is purely a human concept, so let's leave non-humans out of this, yeah? What monkeys understand about human concepts have nothing to do with "intelligence" being definable. "Literature" is only possible to be appreciated by humans because it is a human convention. Does that make sense to you? Do you understand what bacteria are saying to each other or thinking? In any case, that doesn't explicitly define what "intelligence" is, if it's even anything at all.