But by that definition, every not-yet-extinct species is intelligent. Or at least, every species that responds in any way to external environment in order to enhance survival and reproduction... which is pretty much every species.
You're assuming a binary extant/extinct dichotomy. That may work on the level of an individual species, but not on the colony level. The colony is simply attempting to propagate itself. So the utility at a given time could be given by something that measures the current size of the colony, the size of its descendants, and some estimate of how much each colony will further propagate.
Fine, but it's still a bogus use of the word "intelligence".