We started in Jackson Hole and entered the park from the south, stayed at Old Faithful one night, drove through the Haydn valley and then stayed at Mammoth Springs for 3 days of wolf hunting in the Lamar Valley. Great trip (went with our alumni association - organized by Orbridge) for all types of photography. Very little snow this year in the north of the park. You could shoot bighorn, elk, pronghorn and bison with modest focal lengths (new 100-400 would be perfect), but if you want to capture wolves, eagles, coyotes and foxes, take the longest lens you have - the Lamar valley is huge and you would be very lucky to get a decent shot with less than the 600 + 2X. Our closest wolf viewing was at a distance where the animal just about filled the frame at 1200mm. Per my first post, I wish I had a 7DMKII on this trip - there was plenty of light, so noise would not be a huge concern and I could have used more pixels on target.