v SOCIAL LIFE OF ANIMALS 79 



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bined activity the migration of birds is at once the most 

 familiar and the most beautiful the gathering together, 

 the excitement before starting, the trial flights, the 

 reliance placed in the leaders. Migration is usually social, 

 and is probably sometimes facilitated by social tradition. 

 4. Beavers.- -That the highly socialised beavers have 

 been exterminated in many countries where they once 

 abounded is no argument against their sociality, for man 

 has ingenuity enough to baffle any organisation. A 

 family of about six members inhabits one house, and in 

 suitable localities secluded and rich in trees many 

 families congregate in a village community. The young 

 leave the parental roof in the summer of their third year, 

 find mates for themselves, and establish IICAV homesteads. 

 The community becomes overcrowded, however, and 

 migrations take place up and down stream, the old lodges 

 being sometimes left to the young couples. It i^ said, 

 moreover, that lazy or otherwise objectionable members 

 may be expelled from the society, and condemned to 

 live alone. Under constraint of fear or human inter- 

 ference, and away from social impulse, beavers may 

 relapse into lazy and careless habits, and in many cases 

 each family lives its life apart ; but in propitious con- 

 ditions their achievements are marvellous. The burrow 

 may rise into a constructed home, and the members of 

 many families may combine in wood-cutting and log- 

 rolling, and yet more markedly in constructing dams 

 and digging canals. Make allowances for the exaggera- 

 tion of enthusiastic observers, but read Mr. Lewis Mor- 

 gan's stories of the evolution of a broken burrow into a 

 comfortable lodge, varying according to the local con- 

 ditions ; of the adaptation of the dams against the lush 

 of floods ; of canals hundreds of feet in length labours 

 without reAvard until they are finished ; of the short- 

 cut waterways across loops of the river ; and of " locks ' 

 where continuous canals are, from the nature of the 

 ground, impossible. The Indians have invested beavers 

 with immortality, but it is enough for us to recognise 

 that they exhibit more sagacity than can be explained 

 by inherited instinct; they often adapt their actions 



