178 CHILDHOOD OF ANIMALS 



immense distances. The similar migrations of hares, Norway rats 

 and lemmings are still better known. The animals keep together by 

 an instinct of gregariousness, and will perish in great numbers if an 

 impassable river or branch of the sea lie across their chosen route. 

 Simultaneous migrations on a smaller scale frequently happen. 

 There is a fine colony of prairie-dogs living on a private estate in 

 Sussex. Recently a number of them, for no obvious reason, as 

 there was plenty of room and plenty of food, moved off more than a 

 mile, crossing very irregular ground, and settled down in another 

 field. Rats or mice will leave a particular house or ship almost 

 in a body, and this habit is useful when it is necessary to get 

 rid of these pests. If for some weeks a few are trapped or poisoned 

 every day, the whole body will desert the dangerous place, and even 

 newcomers, in search of convenient quarters, will refuse to settle 

 down for weeks or months. 



Rodents usually follow the mother, and afterwards each other, in 

 single file, running along in well-marked tracks leading from their 

 bolt-holes to the feeding-grounds. The South American coypu; 

 a large aquatic rodent, makes a burrow in the bank of a lake or 

 stream with the aperture under the water-level, or, if there is not 

 a suitable position for this kind of nursery, constructs a platform- 

 nest in the thick reeds alongside a stream. Six to nine young are 

 produced at a time, active and furry, and are very soon able to follow 

 the mother to the water. There some of them cHmb on her back and 

 are carried about as she swims, whilst the others swim alongside. 

 The nipples of the milk glands, instead of being placed in the usual 

 fashion on the under surface of the mother, are arranged in a row at 

 each side, very high up and nearer the middle line of the back, so that 

 the young are able to suckle either as they swim alongside or as 

 they crouch on the back. 



Very little is known as to the breeding habits of sloths, armadillos 

 and anteaters. Sloths spend their whole lives in trees, sluggishly 

 creeping along the lower sides of branches, to which they hang by 

 their curved claws. The young are born fully developed, no special 

 nest being made, and are carried about by the mother, clinging to 

 her hair with their long claws and clasping her firmly round the 

 neck with their arms. Anteaters use their powerful claws, not for 

 burrowing, but for digging out the ants and termites on which they 

 feed. They make a lair in thick brushwood, and so far as is known 

 produce a single young one at a time. This is fully clothed, and is 

 carried about by the mother on her back for many months. The 



