246 
JOURNAL OF MAMMALOGY 
ground passages and there is an absence of filth around them. The 
living quarters are generally filthy. 
The larger a nest becomes the greater is the amount of work required 
to maintain it. Its length of life extends over a number of years of 
slow growth followed by a comparatively rapid decay when the forces 
of nature have become too great to overcome. In wet weather the 
nests absorb a large amount of moisture which is held for a long period 
and adds very materially to the rapidity of the decay. Then there 
comes the long, dry, desiccating summer weather when the soft materials 
crumble to dust. 
The rats are not satisfied with the underground retreats for they 
build small refuge nests high up in the trees in the vicinity of the 
ground neSt. When driven from the safety of the latter they will take 
to the trees and finally seek the shelter of the tree nests. A sudden 
sharp blow upon the ground nest will frequently scare a rat into the 
trees and on rare occasions one will go directly to the tree nest. More 
often the rat will remain in the vicinity of the main nest until compelled 
by force to leave it. If a person begins to dismantle a nest at the top 
the rats will seek the underground passages and none will be seen on 
the surface. I have succeeded in driving out one rat but have not been 
able to get sight of a second in any nest. 
I once dismantled a nest that had reached its maximum development 
in an exceptionally favorable location. One side of a huge redwood 
stump had been burned in a fire and then broken off leaving a stub 
on one side while the fire continued to eat its way down the other into 
the roots. The side exposed to the heavy weather remained standing 
and the inner portion of it formed the bracing side for the nest. Against 
this upstanding slab there was piled an enormous amount of trash. 
Beginning carefully at the top I removed a considerable pile of coarse 
sticks and rubbish, finding only a few small open chambers. When I 
had reduced the pile by fully three-quarters of its original bulk I came 
to a large chamber. This chamber was larger than usual but had not 
been cleaned out at the end of the rainy season and was very filthy. 
In one corner there was a small nest such as some bird might build. 
This nest was carefully woven of fine long grass and wood chewed into 
a resemblance to excelsior. The center was perfectly hollowed out 
and lined with soft fur. It was some five inches in diameter and four 
inches deep. This nest had been recently occupied and the young I 
think had been removed to some underground passage. 
