582 University of California Publications in Zoology — | Vou. 17 
Arrangements are always made for the proper drainage of the bur- 
rows, and in wet hillsides water often runs continuously from the 
lower tunnels. In some places the courses of streams are diverted, 
though perhaps accidentally. The mountain beaver is not aquatic in 
any true sense, but is often caught in traps set in the water running 
through the burrows. The animal is said to dip its fore feet in water 
and to wash its head. 
SENSE PERCEPTION 
Sight and hearing seem to be relatively defective in the mountain 
beaver (see fig. 6). The individual comes in contact with its under- 
ground environment chiefly through the sense of feeling, and this is 
markedly developed all over the body. The slightest touch upon a 
hair will be responded to instantly by quick jerking movements. The 
sense of smell seems to be good, for the animal has a way of frequently 
raising its nose to sniff; also the scent glands are well developed. 
BREEDING Hasits 
Almost nothing is known concerning the breeding habits of any 
of the forms of this interesting genus. Lord (1866, pp. 346-358), 
speaking of Aplodontia rufa columbiana as observed upon the banks 
of the ‘‘Chilukweyuk River’’ in British Columbia, asserts that the 
female has from four to six young at a birth and about two litters a 
year; and that the nest is like a rabbit’s, made of grass and leaves, 
and is placed at the end of a deep burrow. Lum (1878, pp. 10-13) 
writes that ‘‘ People living in the vicinity of these animals [A. r. rufa ?, 
in Oregon ?] tell me that the young show’tls just weaned make their 
appearance during the month of June in numbers from three to five 
at a birth.”’ 
VOICE 
The only sound that we have known the mountain beaver to make 
is a singular grating noise produced when the animal is alarmed, by 
rasping the lower incisors laterally across the tips of the upper. I 
have seen pocket gophers, marmots, and copper-headed ground squir- 
rels (Callospermophilus) do the same when terrified. 
Aplodontia has been eredited with a real voice, but the chances 
for error in most of the following reported observations in this regard 
are very great. Suckley and Gibbs (1860, p. 124) quote a certain 
Colonel Simmons as saying that he had seen mountain beavers ‘‘sitting 
