1918] Camp: Burrows of the Rodent Aplodontia 525 
fringes along the streams. At Chinquapin, 6200 feet altitude, in the 
Park, a tunnel (see fig. 3) of Aplodontia rufa californica was exca- 
vated for a distance of twelve yards along the steep bank of a stream 
without the discovery of a single side branch of importance. Only 
two individuals, male and female, were captured in this tunnel. The 
burrows in the colony at Chinquapin were far scattered along-stream 
owing to the narrowness of the area available to the animals. At 
many other localities in the Park similar conditions prevailed (see 
fig. 4). Small colonies with more complicated systems of runways are 
sometimes established where conditions will allow, as, for example, in 
willow thickets bordering meadows and, high up in the mountains, in 
Labrador tea and willows along creeks and about springs. In almost 
every colony tunnels were found containing running water. At one 
place the entire flow of a small stream was taken care of for some 
distance below ground. 
The burrows of Aplodontia rufa rufa of the Trinity and Siskiyou 
mountains, to Judge from the descriptions given by Kelloge (1916, 
pp. 369-372) and Alexander (MS, 1911), appear to be similar to the 
more simple type of tunnel system of A. r. californica. Even in one 
exceptional case where the ground was found to be ‘‘literally honey- 
(a3 
combed’’ by burrows and runways, a ‘‘main tunnel’’ could be dis- 
tinguished. As with californica never more than one pair of animals 
was secured from a single set of runways. 
Foop 
A wide range of plant species is eaten by the mountain beaver. 
The number used for food at a single locality generally includes most 
of the species of shrubs and young trees within reach of the burrows. 
However, a marked preference is often shown for one particular 
plant. Those kinds with succulent stems, when available, take prece- 
dence over the more woody ones. The coast species of aplodontia are 
predominantly fern and root eaters. The following table provides 
record of the plants known to be eaten by various races of the moun- 
tain beaver. 
