"Though they sometimes live together in such numbers that 
their burrows fairly honeycomb the ground, the activities 
of the individual seem to concern only itself and are no 
way related to the common good. It can not properly be 
said of them, therefore, that they live in colonies. In 
the struggle for existence they are merely crowded to- 
gether sometimes by the necessities of environmental con- 
ditions - food, shelter, soil. When kept in captivity 
they do not huddle together in their common fear and de- 
jection, but appear grouchy, each resenting fiercely the 
slightest contact with its fellow." 
Harry D. Hartwell (personal communication) said that mountain beaver 
fight continually when two animals are placed in small holding pens. He 
observed captive mountain beaver fighting in a 1/4=acre enclosure. Even 
provision of separate housing units failed to prevent fighting between 
captive animals. 
ACTIVITY 
Daily 
The nocturnal nature of the mountain beaver is well documented. 
Rafinesque (1817) stated that the animal is chiefly nocturnal. Grinnell 
and Storer (1924) referred to the animal as reclusive and nocturnal, 
Dailey (1936) alluded to the mountain beaver's nocturnal activity. 
Scheffer (1929) believed that the rodent is active in its burrow during 
the day and leaves it only at night. Dalquest (1948) found that, al- 
though principally active at night, the mountain beaver is frequently 
seen during the day in the autumn. 
Ingles (1959) studied the daily activity of the mountain beaver. 
He found that during the summer the rodent had 6 or 7 feeding periods 
within each 24 hours, He stated that the animal was 50 to 60 percent 
active at night, since food was obtained at equal risk. He did not 
think that the nocturnal activity of the mountain beaver was attributed 
to the absence of nocturnal predators -- the coyote (Canis latrans) and the 
great horned owl (Bubo virginianus). Pilleri (1960) said that the mountain 
beaver had poor eyesight and was affected by bright light, which soon 
caused it to become drowsy. 

Seasonal 
Cooper (1860) wrote of an old Indian hunter who frequently saw 
mountain beaver running on top of the snow in the Nisqually Valley, 
Washington. Suckley (1860) learned from the Nisqually Indians that the 
animal moves about a little during the winter but does not become decidedly 
active until late in the spring. Matteson (1877) believed that the moun~ 
tain beaver hibernates. Bretherton (1895) said that it did not hibernate. 
Camp (1918) stated that the rodent is active during the winter, even in the 
high mountains. Howell (1924) wrote that the mountain beaver was active 
20 
