was alone at the water fountain drinking. He was 
shortly joined by the dominant male 49. They 
drank amicably together, nearly side by side, for a 
moment. Then male 49 turned toward male 690. 
With this signal of intent to approach by male 49, 
male 690 jumped and ran away. 
There is some evidence that the thirst drive holds 
dominance over the hunger drive. 
1. November 25, 1947. 5:45 to 6:30 p.m. Al- 
though 5 days of accumulation of garbage 
from my home had been placed in the pen 
this afternoon rats paid surprisingly little 
attention to this food and none at all to the 
Purina checkers. However, hardly a rat 
entered the pen without taking a long drink 
at one of the fountains. 
2. October 7, 1948. 12:30 to 3:45 p.m. All 
rats which came into the Food Pen drank, 
whether or not they ate. 
3. In my notes there are 16 records of recognized 
individuals who after entering the Food Pen 
both ate and drank before departing. 
In 14 of these 16 instances the rat drank before 
it ate. There are many records of rats just eating 
or just drinking when they entered the Food Pen. 
However, the few records above presumably per- 
tain to those individuals in which both the hunger 
and thirst drives were sufficiently high to require 
satisfaction before returning toward the harborage. 
At an open water source the obtaining of the 
water is by one of two methods. The rat either 
bends over and laps the water directly with its 
tongue, or it will first dip in its forepaws and lick 
off the water. Probably the former is the more 
frequent behavior. In either case grooming fre- 
quently follows drinking. In this process the rat 
sits on its haunches and extends a forepaw back- 
ward to and around the ear, dorsally over the head, 
across the eye, and toward the mouth. The hands 
are rotated alternately and rapidly with an oc- 
casional licking of them. Upon completion of the 
grooming of the head the rat bends to one side and 
begins grooming the fur of the back, sides and 
abdomen with both paws and mouth. This is 
followed by a cleaning of the genital region. With 
one or both forefeet on the ground a hind leg is 
extended forward and groomed with the mouth. 
The tail is picked up with the forefeet and licked. 
With some variation this in general depicts the 
order of grooming. Although grooming may occur 
at practically any point where the rat has stopped 
momentarily, it is most frequently associated with 
drinking. 
Dew and rain on the foliage served as accessory 
sources of water. The habit of licking off this 
moisture was noticed among the initial rats intro- 
duced into the pen as well as later when the popu- 
lation was quite dense. Presumably, the utiliza- 
tion of this occasional source of water may have 
reduced the social conflicts associated with the 
approach toward the Food Pen. However, this 
was probably of little import. At least on several 
occasions in the early morning hours rats were seen 
to congregate about the water fountain despite the 
presence of extremely wet, to the point of dripping, 
foliage. 
K. Elimination Behavior , The actual act of defe- 
cation or urination was seldom observed. How- 
ever, the distribution of spots, where urine could 
be seen or where there were feces, provided con- 
siderable indirect insight into these behaviors. 
Regarding feces: 
1 . Defecation occurred wherever the locomotion 
of the rat was temporarily inhibited. This is 
the most important generalization regarding 
the place of defecation. Most of the addi- 
tional statements concerning locations of feces 
are merely corollaries of this. 
2. Few feces occurred along the 3-foot wide paths 
from the corners of the Food Pen to the pas- 
sages through the median barrier fence, 
except at the points where the trail down this 
path was intersected by a trail entering from 
the adjoining vegetation. At such points 
aggregations of feces might occur in a perfectly 
clear and unsheltered place. It will be re- 
called that these 3-foot wide paths were kept 
cleared of vegetation to facilitate observation. 
3. Along trails through the vegetation the great- 
est concentration of feces occurred at intersec- 
tion of trails. However, even along trails 
away from intersections more feces occurred 
than along similar stretches on trails over the 
cleared paths. This presumably resulted from 
the effect of the overhead shelter of the vegeta- 
tion in temporarily halting locomotion. 
4. Along the trails immediately adjacent to the 
outer limiting fence feces were no more con- 
centrated at intersections of trails leading out 
into the areas than they were at any points 
intervening between such intersections. Char- 
acteristics of the situation and the behavior of 
the rats themselves suggest possible processes 
110 
