There is a gray wolf population north of the Saint Lawrence River (not that far from Maine). There have been rare sightings and I think one carcass of a gray wolf found in Northern Maine. Speculation is that males cast out from a pack occasionally roam south but there is no known breeding population. There is also genetic evidence of some cross breeding of Coyotes and Gray Wolves but its also that coyote population has filled the ecological niche of the wolves along the border in Maine so they have gradually gotten larger to better fill the niche. Southern Maine along the developed coast is loaded with white tail deer but inland the industrial forests are managed for softwood and the white tail population is far lower thus not a lot of feed for a wolf pack. Coyotes are more opportunistic and live off whatever they can find and thus a better fit for the current condition of the woods.