The famous large bear concentrations at McNeil River, Brookes Falls or Silver Salmon Creek doesn't happen until July & August when the Sockeye Salmon runs up the rivers. For bear photography in May or June, I would go to Denali National Park. I would spend a week at Denali NP. Spend at least one night at Wonder Lake to get the "Wonder Lake with Denali in the background photo". You would have great chances of photographing Dall Sheep, Moose, Caribou, Bear, Beaver, Pika, etc. When I go to Denali, I take my 200 -400mm or my 600mm lenses for my long lens.