96 THE BEAVER 
It has not been easy to obtain any definite information 
as to the length of time required to form a beaver meadow, 
and we are fortunate in having some data concerning the 
meadow on Lost Creek, above Yancey’s, Yellowstone Park. 
In 1897 there were at this place long dams and large ponds 
which Seton mapped and described, and which were in- 
habited by a flourishing colony of beavers. In 1912 Seton 
revisited the place and found the colony abandoned and the 
meadow pretty well formed. The beavers, according to M. 
P. Skinner, formerly park naturalist, began to desert the 
place about 1903 or 1904. In 1921 I examined the ground 
and found most of it solid, and the dams, except the two 
upper longest ones, so nearly obliterated that it was difficult 
to locate their sites. ‘Thus in perhaps twelve or fifteen years 
these meadows assumed their present form. 
There is a wide valley here, bounded by hills, and traversed 
by Lost and Elk Creeks, which is one large beaver meadow. 
The old Yancey place is situated at the forks of these 
streams, and Yancey used to cut hay near his place twenty- 
five or thirty years ago. Since 1920 the National Park 
Service has been cutting hay here for its own use. Some of 
the ground is still too soft for the use of a mowing machine. 
I have information that in 1907 there was a beaver colony 
on Lost Creek toward the northeasterly part of this area. 
This is now like the rest of the meadow. Thus it would 
appear that this meadow is not all of the same age, but was 
formed at different times, the portion at the junction of the 
streams being the oldest (Fig. 46). 
Another instance in Yellowstone Park is the case of the 
lowest pond in what I called the “Bench Colony.’’ When I 
first examined this July 23, 1921, it was full of water (Fig. 
48). This gradually receded during the summer, and when 
I saw the pond for the last time that year, September 4, 
it was more mud flat than pond (Fig. 49). Figure 50, 
