The Canadian fish-otter (_Lutra Canadensis_) loves to do the same thing. He climbs to the top of a snow-ridge in winter, or of a slippery bank in summer, lies on his belly, with the fore feet bent backward, then, pushing with the hind legs, down he goes. So the Russians, with their ice-slides, are only imitating the sport of their own arctic creatures. I suppose that long ago the pleasure derived from an involuntary and accidental slide originated the habit.
Lieutenant Dall says that the beavers in Alaska engage in gymnastics for fun. If they find a smooth, miry bank, they betake themselves to sliding down it. And the Californian gray whale loves to play in the shoals where the surf breaks; keeping a wary outlook, so that it continually escapes being beached. Its pleasure is enhanced by the peril. Seals do the same thing when they find a heavy surf. They turn from side to side with half-extended fins, moved apparently by the heavy ground-swell; at times making a playful spring with bended flukes that throws the body clear out of the water, to come down with a heavy splash: then, giving two or three spouts, they settle again under water, to appear perhaps the next moment rolling over in a listless manner with the heavy swell, plainly full of intense enjoyment.
If the sea-otter of Siberia escapes into the water from its hunters, it expresses joy and derision by marked gestures, one of which is the putting a paw up over the eyes, as if shading them to regard the hunters. It would seem to be a very slight natural variation when the thumb slips to the point of the nose, and the rest of the paw executes that vibratory sarcastic gesture highly approved by boys.
The same sea-otter will mourn itself to a skeleton over the loss of its young. If animals can be capable of grief, as innumerable facts testify, mirth ought to endow them with a finite compensation.
Lady Barker, in her book called "Station Life in New Zealand," describes a favorite cockatoo, whose amusement consisted in imitating a hawk. "He reserves this fine piece of acting until his mistress is feeding the poultry; then, when all the hens and chickens, turkeys and pigeons are in the quiet enjoyment of their breakfast or supper, the peculiar shrill cry of a hawk is heard overhead, and the bird is seen circling in the air, uttering a scream occasionally. The fowls never find out that it is a hoax, but run to shelter, cackling in the greatest alarm; hens clucking loudly for their chicks, turkeys crouching under the bushes, the pigeons taking refuge in their house. As soon as the ground is quite clear, the bird changes his wild note for peals of laughter from a high tree, and finally, alighting on the top of a hen-coop filled with trembling chickens, remarks, in a suffocated voice, 'You'll be the death of me.'"