ECOLOGY 
Habitat 
The mountain beaver is found at elevations from sea level to 10,000 
feet. Scheffer (1929) stated that it inhabits almost any wooded situa-~ 
tion where soil conditions permit easy burrowing. It occurs on hillsides, 
old burns, logged-off land, along roadside clearings, and on the tops of 
high ridges and mountains (fig. 5). The animal is dependent upon an 
abundant supply of boreal plants of riparian growth. It is most abundant 
near springs, streams, and damp places. Dalquest (1948) wrote that 
clearings are the principal habitat of the mountain beaver. 
Common signs of mountain beaver are trimmed and pruned bushes, shrubs, 
and trees, and earth honeycombed with tunnels. 
Burrows and Nests 
The mountain beaver has extensive irregular tunnels forming a network 
of passages a few inches beneath the ground surface with many entrances 
and roof openings (cave-in). Unlike the pocket gopher (Thomomys) or the 
mole (Scapanus), the mountain beaver does not repair the roof openings. 
However, it keeps its tunnels clear and uses the roof openings to push 
out excavated earth and debris (fig. 6). Ingles (1959) said that at times 
the animal may emerge from any one of the many roof openings and feed 
unobserved, 
Camp (1918) wrote that the unplugged burrows are so well concealed 
beneath tangled vegetation that the presence of the rodent is often un- 
known to persons resident in the immediate vicinity. The main tunnels 
are 4 to 8 inches in diameter. Connected to the tunnels are enlargements 
for nests or for temporary food storage. 
Scheffer (1929) excavated a nest. It was located under the roots of 
a fallen tree. The nest was oval, 20 inches high and 13 inches wide. 
It contained leaves and stems of bracken fern laced together with grass 
and small twigs. The nest was protected from flooding by a basin 6 inches 
beneath the nest. Two drainage tunnels led away from this basin. 
Abundance 
Wherever the mountain beaver lives, it digs extensive tunnels. Each 
tunnel system has many burrow openings (fig. 7). The grouping of tunnel 
systems and openings in an area suggest a flourishing colony and that 
mountain beavers are abundant, 
Camp (1918) wrote that overcrowded conditions may occur in one area, 
while nearby areas of similar environment remain unoccupied. From an 
area of 100 by 500 feet, containing about 100 burrow entrances, he trapped 
11 mountain beavers in 169 trap-nights. In the last 46 trap-nights no 
mountain beavers were captured. Camp concluded that the 11 captures 
approximated the total population of that particular area of the colony. 
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