Tom Reichner wrote in post #8455372
Yeah, it used to be like that . . . Bison and Elk, with perhaps a slim chance at a Black Bear. I remember back in '95 being there an entire week and only seeing one bear - a Black Bear. Same in '97 - whole week, only one bear. We'd hear so many people complaining that all they wanted to see was a bear, and that they hadn't seen one the whole week they were there.
Not like that anymore! In my experience, bears are now much more commonly seen, with the Grizzlies being seen just as frequently as the blacks. Coyotes are more often seen (at least the habituated ones that let you get close). Bighorn Sheep also seem to be more regularly seen at close range. And now we have the wolves, too.
In 1968, Yellowstone decided to close down the garbage dumps where grizzly and black bears were allowed to feed. Against the advice of grizzly research pioneers the Craigheads, the Park Service closed the dumps immediately rather than tapering off. The dumps were closed in part as a fast reaction to the famous Glacier NP grizzly deaths of 1967(which were also bears that ate garbage). There were liability concerns.
By 1975, there were around 150 grizzly bears in Yellowstone. Closing the dumps essentially cut off a source of food and the population crashed. At this point, the feds intervened and placed the grizzly bear as threatened under the very new endangered species act. This protection essentially allowed the bears to recover over the next 35 years. How did they recover? Well ,the designation banned ranchers from shooting them on sight. It made timber and oil companies have to jump through several hurdles on bordering national forest land. Grazing allotments were phased out around the park to give the bears room to roam. This essentially alowed the bears to not only repopulate Yellowstone park, but the very rich grizzly habitat which surrounds the park in national forest land (the Shoshone, Gallatin, Bridger-Teton). A 6 month jail sentence and 25,000 fine for killing a grizz didn't hurt either. 
That is why you see more now than you did twenty years ago. Currently there are around 500-700 grizzly bears in the Yellowstone ecosystem, which is a far cry from 150 or so in 1975. If it wasn't for the Endangered Species Act we wouldn't be talking about Yellowstone grizzlies today. Fortunately the population crash of the 70's did not harm genetic diversity too badly.