502 NATURAL HISTORY. 



One of the porcupine-like forms — like the porcupine in structure, but 

 not in appearance — is the celebrated coypu of South America, which 

 furnishes the nutria fur of commerce. The coypu is about the size of a 

 beaver ; it is like an otter in its habits, living on the banks of rivers, and 

 swimming by means of its webbed feet, with the greatest ease. Its fur is 

 brown and soft, and as these animals are very abundant, and easily 

 obtained, they have tended to reduce the price and demand for the beaver- 

 skins of North America. 



The jerboas of the warmer parts of the Old World are the kangaroos 

 of the rodents. As in those animals, the fore legs are short and weak, 

 while the hind ones are enormously developed, and the animal but rarely 

 attempts any progress except that of jumping. Its leaps are enormous in 

 proportion to the size of the animal ; it merely touches the tips of the toes 

 to the ground, and with its long, tufted tail streaming behind, it seems 

 rather to fly than to move by means of its feet. In our jumping-mouse 

 these leaping powers are not so well developed, but still they are consid- 

 erable. When moving about in the ordinary manner the animal uses the 

 fore feet as well as the hind legs ; but when alarmed, only the latter are 

 called into action, and the animal can then jump six or eight feet at a 

 bound. The late Professor Tenney gave some account of this species, and 

 especially its hibernating habits, an abstract of which may prove interest- 

 ing. The animal was found in January, coiled up in its nest two feet 

 below the surface of the earth, and to all appearance dead, except that 

 possibly it was not as rigid as a dead mouse would be in winter. It was 

 taken home, and after being held in the hand for some time it began to 

 show signs of coming to, and in the same afternoon it became perfectly 

 active. It was given food and materials for making a nest, and as soon as 

 the lights were put out it began its gnawing, and by morning it had a ball 

 of paper and cotton about six inches in diameter, and was snugly ensconsed 

 in the middle of it. The next night was cold, and in the morning the 

 mouse was seen on the outside of the nest apparently dead. So it went 

 on all winter ; cold making it torpid, and warmth reviving it and restoring 

 it to a state of activity. 



The pocket-mice are somewhat similar to the jumping-mouse in appear- 

 ance and habits, and form a transition between them and the gophers. 

 Some of them jump as well as the form just mentioned, and all are char- 

 acterized by having pouches in the cheeks. These pouches, or pockets, do 

 not communicate with the mouth, but open at the sides, and are lined like 

 the external skin with fur. They are somewhat nocturnal in their habits, 

 and while they are frequently seen by day, it is only after dark that they 

 display their greatest activity. They are all confined to the district west 



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