The black bear is a playful bluffer. One day, as I was seated on the edge of Yellowstone Lake, several feet above the water, a young black bear came ambling by. In passing, he leaped at me with a wild "woof." His bluff was effective. I shrank back, and tumbled into the lake. The creation of the Yellowstone National Park, for "the benefit and enjoyment of the people," was one of the great achievements for mankind. It also was a great event in the world of wild folk. The Yellowstone is one of the greatest wild-life sanctuaries in the world. In its thirty-three hundred square miles are numerous varieties of wild animals. Each summer as many as sixty thousand elk feed in it, and there are also buffaloes and antelopes, and flocks of sheep and herds of moose. Black bears are on every hand, and grizzly bears are often seen near by. The caribou of the North make a long north-and-south migration with the seasons. The deer and the elk of the mountain parks, like many birds, simply migrate up and down the heights, spending summers in the high altitudes and winters in the foothills. On the thousand hills, meadows, crags, and moorlands of the National Parks are herds, flocks, and bands of elk and moose and deer and the agile mountain sheep. There are more than five hundred kinds of birds. A census of wild-life folk in all National Parks would show a numerous population: possibly a hundred thousand elk, half as many deer, several thousand sheep, a few thousand goats, several hundred antelopes, a few hundred moose, a thousand or so of bears, many thousand beavers; minks, conies, marmots, and muskrats in uncountable thousands; and birds in untold millions. The antelope is a strange, isolated species. Formerly it ranged widely over the plains, but now it is almost exterminated. It has no dewclaw. It can erect and depress its fluff of white tail at will; this is a means of signaling. Of all big game, the antelope perhaps is the fastest runner. This animal sheds the outer part of the horns each year, retaining the spikelike core. The gray wolf, coyote, fox, lynx, otter, skunk, and porcupine are numerous in the Parks. The porcupine, even at his wildest, shows the least signs of fear and is the dullest-witted animal in the woods. Glacier Park probably excels in the number of mountain goats. Here they are to be seen in one of the most picturesque and precipitous ranges, in topography which goats enjoy. The Rocky Mountain Park probably excels in the number of bighorn sheep. Along the streams the picturesque beaver, a permanent home-builder, lately almost exterminated, is reëstablishing himself and restoring the scenes that were known to the pioneers.