I've lived in Gardiner now for over a year and I'm out shooting, depending on the time of year, 3 to 6 days a week from sunrise to sunset. As
@Steve indicates, animal sightings are very seasonal. At the moment there is a lot of grizzly activity along the East Entrance road from the Mary Bay and Sedge Bay areas east to the Teton Overlook. This is the area where the grizzlies Jam, Snow and her two cubs, Raspberry, and a couple more, hang out. On your way there, you'll pass the Mud Volcano, just past Hayden Valley, where griz 864 and her two cubs hang out (however, it appears 864 just recently kicked her cubs out). If you continue further East past the Teton Overlook there is a good chance you will see Bighorn Sheep beyond the Sylvan Lake area. In addition, the long stretch of road beginning from Phantom Lake along the North Loop to Tower Falls, which passes by Blacktail Pond and the Northeast Entrance Road has seen a great deal of black bear activity (to include some beautiful Cinnamon Black Bears) with cubs. There has also been some grizzly activity there as well. If you're interested in Harlequin Ducks, LeHardy Rapids on the Yellowstone River is where they are currently located and will be there until July. You will pass the Rapids on the way to the East Entrance and before Fishing Bridge. Beginning now and for the next couple of months, the indigenous trout begin heading towards their breeding grounds in Yellowstone Lake, near Pelican Bay, and from LeHardy rapids you can photograph them jumping upstream. I have a great shot of that from last year. Have not yet seen them jumping yet this year. If you're headed south from Mammoth towards Norris Junction, along that road in the area of Roaring Mountain and Frying Pan Creek the Grizzly Beryl with her two cubs have been spotted quite often and the Grizzly Obsidian with her three cubs has also been spotted. I've photographed Beryl and her cubs in that area just this past week and though I have yet to see Obsidian, I believe my sources to be reliable and accurate. I have found, and many can quibble with me, that but both Lamar and Hayden Valleys haven't offered me consistently good shooting opportunities because the animals are frequently just too far away. Having said that, however, I have gotten good shots of Coyotes there and a couple wolves in Lamar, and also a great shooting opportunity of a Bobcat this Spring. If you're looking for wolves, just keep an eye out for fairly large groups of folks with scopes. These are the "wolfies." Pull over, introduce yourself politely, and because 99% of them are extremely nice and helpful, they will let you look at the wolves through their spotting scopes. Places for wolves include Slough Creek where the Junction Butte Pack has denned, Jasper's Bench (possibly) in Lamar Valley and places I don't know in Hayden Valley because I spend little time shooting dots on the horizon. If you're looking for Osprey, there is a nest prominently exposed and visible just west of the western end of the Lamar Canyon with a large pull out. It's near the construction site. There is an area on the way to Mary and Sedge bays called Storm Point and Indian Pond that is just East of Fishing Bridge, where there are trails leading to Yellowstone Lake. This area is known for Great Gray Owls, but while people swear by it for the owls, I've turned up nothing yet - though, I'm not done. Just a word of warning that it is an active bear area, do not walk the paths alone, go in groups, carry bear spray, and be very careful. Hope this helps the folks headed for Yellowstone prior to the middle of July. My experience is by mid-July the animals change their patterns and head for higher ground and different food sources. One last thing, don't over look taking the Old Yellowstone Trail leading out of Gardiner. It's a dirt road and there are elk and bighorn sheep to be seem along with pronghorns. July thru December, but mostly October/November is the bighorn rut, and it is something to see. The rut for elk begins September thru October. Bison rut occurs in August-September. Bear rut is now through June. If your're looking for moose, the Tetons is the place to go September through December primarily along the Gros Ventre Road near the campground. Well, that's all I have. Hope it helps