THE ARCHITECTURE OF A BEAVER DAM. 



FRANK R. GROVER. 



For several years the old beaver dams on 

 some of the trout streams in the wildest 

 woods of Northern Michigan, around the 

 straits of Mackinac and Les Cheneaux 

 islands, where 1 have passed many sum- 

 mer vacations, have been an interesting 

 study. Last summer it was my good for- 

 tune to see a new beaver dam just receiving 

 the finishing touches by a colony of these 

 interesting and industrious creatures. I 

 was not looking for beaver dams, but for 

 brook trout. A young native, a chance 

 acquaintance of the year before, described 

 the "great big trout you kin ketch up by 

 the old river dam, jest a mile or 2," and he 

 was engaged to show me the place. A 

 tramp of the Michigan "mile or 2" took us 

 to a new place on Taylor's creek, a stream 

 I had known in part for many years, and 

 which is head waters of the Munuskong 

 river. The usual wading of the stream 

 and crawling through the thick brush and 

 over fallen logs, in following the creek 

 toward its source, then ensued. We soon 

 reached our supposed destination, when my 

 guide exclaimed, 



"Why ! the dam is gone !" 



Sure enough there was the wreck of an 

 old beaver dam that had lately been washed 

 away. The next instant I heard the boy 

 say, 



"See, they have built a new one, and the 

 little rascals have built it in 2 weeks. The 

 last time I was up it wasn't here at all." 



About 30 rods up the stream was the new 

 dam, in plain sight, and it was of such in- 

 terest that I soon let the trout go and 

 spent several hours examining the beaver 

 work. The main part of the dam was in a 

 narrow part of the stream, where the banks 

 were comparatively high and rocky. From 

 the down stream side it looked much as if 

 a pile of brush coming down stream had 

 caught on the banks, with this exception: 

 The brush was mostly green and freshly 

 cut. This part of the dam was about 20 

 to 25 feet long and about 5 feet high. A 

 close examination, however, disclosed that 

 under and among this mass of brush 

 were ingeniously placed, in all sorts of ef- 

 fective positions, short poplar and birch 

 logs, freshly cut, 3 to 6 inches in 

 diameter and 2 to 3 feet long. Not a 

 drop of water seemed to come through the 

 dam. At the top it had a sharp and well 

 defined ridge like that of the roof of a 

 house, the slopes running both up and 

 down stream. On the upper side the brush 

 and logs had been neatly plastered with 



mud dug from the bottom of the creek, 

 for the stream at the beginning of the 

 slope, toward the apex of the dam, 

 was over 10 feet deep. The depth 

 of water below was less than 2 

 feet. The loss of the old dam seemed to 

 have taught the necessity of guarding 

 against the washing away of the new one, 

 for near it, up stream, was a heavy pine 

 log, partly submerged, extending across the 

 stream in such position as to catch float- 

 ing ice and driftwood. 



The architects and builders had been at 

 work the night before. On either side of 

 the stream, and following its banks for 100 

 yards, was a low dam, or sort of dike, one 

 to 2 feet high, leading to the dam proper 

 and converging from the dam up stream 

 like a funnel. This dike was constructed 

 in the same manner, except that the logs 

 were smaller and shorter, and the dike ex- 

 tended above the level of the stream to meet 

 the requirements of the colony in high 

 water. The mud and clay plastering was 

 fresh ; and that the beavers' tails had been 

 used as trowels, which is sometimes ques- 

 tioned, was plainly shown by the filelike 

 troweling, which was so regular and work- 

 manlike that even a full fledged union 

 mason might well have been proud of the 

 job. While some of this work had evi- 

 dently been done with the paws, the fresh 

 troweling by the tail was unmistakable. 

 This dam, thus constructed, made a pond of 

 some 10 acres, in which were standing wil- 

 lows and birch and poplar trees ; both food 

 and building material. 



Along and near the banks the many 

 stumps oi birches and poplars showed 

 where the logs and brush for the dam had 

 come from; also that further operations 

 were contemplated and in progress. Here 

 and there was a log freshly cut into many 

 pieces, and even in length, as if some 

 farmer had been on the ground to re- 

 plenish his wood pile. The chips, too, 

 were interesting ; cut in the same man- 

 ner, as if by a woodman's axe, their length 

 varying from 2 to 4 inches, according to 

 the size of the log. In the green 

 bark of some of the pieces adjacent to 

 the actual cutting, the crescent shaped 

 tooth marks of some old patriarch of the 

 colony were clearly defined, fully ^ of an 

 inch in length. I did not succeed in see- 

 ing the foreman, the architect, or even 

 one of the common laborers, but oily water 

 around some of these fresh cuttings in- 

 dicated that the builders had left a few 



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