I know a movie that's so obscure I can't even find it on imdb, or find a shot of the cover anywhere. It looked like it was filmed in the 70's, but was probably low-budget early 80's, and it was about some nerdy looking guy and his girlfriend (possibly some others) who were out in the forest camping, getting attacked by a bear. I remember the title came at the same time an airplane landed/took off, and the bear died from falling off a cliff. Notable moments include the protag running off into the forest chasing a butterfly like a retard, leaving his girl alone to be attacked by the bear (could also have been a roving gang of rapists). The bear varied wildly in size from shot to shot.
It's not Grizzly.