There is an old saying that "if you pick up a guinea pig by the tail, its eyes will drop out." Since the caudal appendage is so short, being a mere vestige, guinea pig eyes seem perfectly safe. How fortunate it is, however, that the guinea pig does not feel called upon to show its feelings in the same way as does the dog, for it would have to wag the whole end of its body energetically to express a happy emotional state.
The muskrat and the beaver have much in common, for both of these rodents live in the vicinity of water, both are very fond of vegetable food, and both build more or less elaborate houses or dens for themselves, but when it comes to tails-the resemblances seemingly end. The muskrat’s tail is flattened vertically along its length, and while it may serve as a rudder in swimming, it is too weak to be used as a beaver uses his. The beaver’s tail, which is flattened cross-wise into a broad, paddle-like appendage, has developed an unusually strong set of muscles, so that it may be maneuvered both easily and effectually. This tool is used particularly in swimming and in personal broadcasting when danger threatens. Loud danger signals are often sent out to fellow beavers by a vigorous slap of the alert one’s tail on the surface of the water.
In remarkable contrast to the types just discussed, the whale and the porpoise have fleshy, bilobed tails, which suggest the fins of fishes but are set cross-wise of the body rather than perpendicular to it. In addition, they lack the bony supporting rays. Like many fishes, both the whale and the porpoise are specialized for life in the open seas.
Again, Nature has been especially generous with the kangaroo, in so far as his tail is concerned, whereas it has decidedly slighted the world’s champion heavy-weights, the elephant, the rhinoceros, and the hippopotamus. So strong is the kangaroo’s large tail that in times of danger it may support the entire weight of the body while the animal kicks viciously with its hind feet. At other times it is regularly used as a prop in sitting or as a spring or propelling force in locomotion. Exactly contrary to this condition, the elephant’s most useful appendage was placed in front of the body instead of behind, while the unlucky hippopotamus was cheated at both ends.