A long-bodied, yellow-brown animal walked out of the woods and paused for a moment by the rapids of a mountain stream. Its body architecture was that of a dachshund, with the stout neck and small upraised head of a sea lion. Leaping into the rushing water it shot the rapids in a spectacular manner. At the bottom of the rapids it climbed out of the water on the bank opposite me and stopped to watch its mate. This one stood at the top of the rapids. It also leaped in and joyfully came down with the torn and speeding water. It joined the other on the bank. Together they climbed to the top of the rapids. Again these daredevils gave a thrilling exhibition of running the rushing water. They were American otter, and this was a part of their fun and play. A single false move and the swift water would have hurled and broken them against projecting rocks. In the third run one clung to the top of a boulder that peeped above the mad, swirling water. The other shot over its back a moment later and endeavoured in passing to kick it off. Though I had frequented the woods for years and had seen numerous otter slides, this was the beginning of my acquaintance with this audacious and capable animal whose play habit and individuality so enliven the wilderness. Play probably is the distinguishing trait of this peculiar animal. He plays regularly--in pairs, in families, or with numbers who appear to meet for this special purpose. Evidently he plays when this is not connected with food getting or mating. He plays in Florida, in the Rocky Mountains, and in Alaska; in every month of the year; in the sunlight, the moonlight, or darkness. The slippery, ever freshly used appearance of bank slides indicates constant play. The best otter play that I ever watched was staged one still winter night by a stream in the Medicine Bow Mountains. The snowy slide lay in the moonlight, with the shadow of a solitary fir tree across it. It extended about forty feet down a steep slope to the river. The slide had not been in use for two nights, but coasters began to appear about nine o’clock. A pair opened the coasting. They climbed up the slope together and came down singly. No others were as yet in sight. But in a few minutes fourteen or more were in the play. Most of the coasters emerged from an open place in the ice over the rapids, but others came down the river over the snow. As the otter population of this region was sparse the attendance probably included the otter representatives of an extensive area. Tracks in the snow showed that four--possibly a family--had come from another stream, travelling over a high intervening ridge four or five miles across. Many may have come twenty miles or farther.