522 Unwersity of California Publications in Zoology — (Vou. 17 
tral Mendocino County coast. The colonies now known extend from 
the town of Point Arena to Alder Creek, seven and one-half miles 
north. In the case of the race phaea colonies oceur in a part of the 
Point Reyes Peninsula and country adjacent, in Marin County, Cali- 
fornia, an area of not more than 110 square miles in all. 
Of a colony of Aplodontia rufa humboldtiana discovered at Cud- 
deback, Humboldt County, California, Stephens (MS, 1910) says: 
I put ten traps in the burrows and did not cover more than half the 
entrances. I saw at least two tunnels run close under the surface, with fre- 
quent openings. My previous idea of a burrowing place for aplodontia is wet 
or springy land. This is far from that. It is a very steep south-facing slope 
almost at the top of a point on a high ridge and is as dry a place as well 
could be found. The location is in an open place in a thick forest of redwood, 
spruce, and fir. It has been burned over three years ago and there is very 
little underbrush. 
Lyon (1907, p. 91), speaking of Aplodontia rufa rainieri, says: 
““The burrows or tunnels are about 8 to 9 inches in diameter and were 
always found in groups or colonies.’’ 
The habitat preferences and burrowing habits of Aplodontia rufa 
rufa appear to be similar to those of the California coast species. 
Matteson (1877, pp. 4384-435) states that the mountain beaver of 
Oregon ‘‘is a digger par excellence and burrows into the sides of the 
hills usually in the neighborhood of a spring.’’ Lum (1878, pp. 
10-13) notes that the species of mountain beaver along the western 
base of the Cascade Mountains ‘‘usually selects the open glades of the 
forest, thickly grown up with fern and sallal’’ (Gaultheria shallon) 
for its burrows. ‘‘Here the ground will be seen perforated with 
holes. . . . Beneath the ground the various openings connect and form 
a perfect plexus of passages often nearly parallel with the surface 
and only a foot or so in depth. . . . In many places I found water 
coursing its way through the passages.’’ 
In California, at the southern part of its range, aplodontia usually 
prefers a shady, north slope for its burrows; but Brooks states (1899, 
pp. 258-259) that the race (Aplodontia rufa columbiana) in British 
Columbia, in the extreme northern end of the range of the genus, 
prefers a locality ‘‘where there is a good thick growth of vegetation 
on the mountain slopes, especially on those with a south exposure.’’ 
Aplodontia rufa californica of the Sierra Nevada, in California, 
has been found in a variety of situations, at elevations all the way 
from 5500 to 10,000 feet. Townsend (1887, pp. 174-175) saw burrows 
near Morgans Springs near Mount Lassen, and on the North Fork of 
