38 Union Bay 



Rocky Mountains, I have seen whole valleys whose surfaces 

 have been leveled by the work of beavers. They have built 

 dams which have been silted up by the spring freshets, and 

 when they are useless the animals have built more, a con- 

 tinuing process which has resulted in the construction of flat 

 and fertile valley floors. 



The threefold virtue of the dams— to provide protection, 

 log transport, and house sites— is quite evident. The deep 

 ponds enable them to build island homes where entrance 

 from below is always possible even when there is surface 

 ice. Easy towing of the floating wood is certain and the soft 

 ooze of the bottom makes possible the sinking and anchoring 

 of the winter feed, which is pushed into the ooze or covered 

 with mud or rocks as required. The beavers stay snug under 

 the frozen roofs of their lodges in winter and as secure from 

 the attacks of predators, except man, as it is possible for such 

 animals to be. 



There is an island about three times as large as a tennis 

 court which was formed by the turn-around of the dredge 

 when making one of the channels of the Arboretum. I had 

 seen a green heron fly from the trees covering it and, as I 

 hoped it might be nesting there, I looked for it on every trip 

 that I made. I had just reached the turn one afternoon when 

 I heard a slight sound which, when checked, proved to be 

 made by a large mammal swimming toward shore. I knew 

 that it was much larger than a muskrat. Its head was shaped 

 wrong for an otter and it did not swim like one. 'The canoe 

 alarmed it and as it dived its broad tail slapped the water 

 with a noise as loud as could be made by the broad side of 

 a canoe paddle. The channel was narrow and the beaver did 

 not reappear but I did not care, for I knew that it had taken 

 up a more or less permanent abode and that I would see it 

 again. The island itself and the north shore offered many real 

 advantages and I hoped that the animal, or animals, would 

 remain in this altogether desirable spot where visitors on 



