74 The Study of Animal Life PART i 



enclosed. Burial beetles unite to bury the dead mouse or 

 bird in which the eggs are laid, and the dung-beetles help 

 one another in rolling balls of food. But of all cases of 

 combined 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 sustained by 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 con- 

 gregate in a village community. The young leave the par- 

 ental roof in the summer of their third year, find mates for 

 themselves, and establish new 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 is said, moreover, that lazy or other- 

 wise objectionable members may be expelled from the society, 

 and condemned to live alone. Under constraint of fear or 

 human interference, 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 

 conditions 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 exaggeration of enthusiastic 

 observers, but read Mr. Lewis Morgan's stories of the evolu- 

 tion of a broken burrow into a comfortable lodge, varying 

 according to the local conditions ; of the adaptation of the 

 dams against the rush of floods ; of canals hundreds of feet 

 in length labours without reward 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 



