520 University of California Publications in Zoology | Vou. 17 
ence of the animals is often unknown to persons resident in even the 
immediate neighborhood. 
The grouping of the burrows in close ‘‘companies’’ may simply 
indicate that the animals are not wont to range widely enough to 
‘ 
invade adjacent districts, though these seemingly might support a 
population of similar extent. Overcrowded conditions may prevail in 
one place, while territory of the same character remains unoccupied 
near by. Near Point Reyes, in the gulches five miles west of Inver- 
ness, Marin County, California, trapping was carried on in 1913 in 
two colonies of Aplodontia rufa phaea. The burrows extended along 
UNOPENED ~<TUNNEL 
4-24 
SCALE 
—————— 
ONE METER 
ooo 
THREE FEET 
Fig. 1. Plan of underground tunnels in colony of Aplodontia rufa phaea 
excavated near Point Reyes, Marin County, California. All tunnels shown were 
within 600 millimeters of surface of ground. 
the side of a low north-facing bluff among bare hills for two miles or 
more. One section of this colony in a rectangular area about 500 by 
100 feet contained at least 100 burrow entrances. Here 169 ‘‘trap- 
nights’’ (one trap out one night equals one trap-night) in thirty-six 
burrow entrances produced eleven specimens. No individuals were 
secured in the last forty-six trap-nights, an indication, perhaps, that 
the catch approximated the total population of that part of the colony. 
Ninety-two trap-nights in another limited part of the above colony 
produced six specimens. 
Some of the burrows in the Point Reyes locality were excavated by 
me (see figs. 1, 2). The floors of many of the runways were seen to be 
tramped hard from long use. It was found that nearly all the burrow 
