approaching the food source, if they entered di- 
rectly into the East Alley from the Food Pen. 
In figure 74 the main tendency of flow of rats 
through the the Food Pen is shown by the system 
of arrows. The development and utilization of 
trails through the central portion of the East Alley 
connecting back to the North and South Alley 
Burrows further substantiates this concept (see 
figs. 14 and 59). 
Of course, rats living out in the triangular areas 
also moved through the alleys into and out of the 
Food Pen. However, it is believed that their 
movements were mainly determined with reference 
to rats living in the two main burrow systems in 
the alleys. Those rats living in Areas II and III 
primarily utilized Passage 6 adjoining the East 
Alley. Furthermore, rats living in Area IV pre- 
dominantly utilized Passage 8 adjoining the West 
Alley. In their movement from Area IV to Pas- 
sage 8 into the Food Pen these rats utilized trails 
which swung toward the center of the West Alley 
prior to being directed more directly toward 
Passage 8. The orientation of these trails through 
the West Alley was such as to insure a reduction of 
contacts with rats living at the North and South 
Alley Burrows (see figs. 14 and 59). Rats from 
Area I with their close social affinity to the members 
of the South Alley Burrow most frequently went 
directly down Path 1 and then at its base around to 
Passages 5 or 8 without much avoidance of the 
South Alley Burrow. Further avoidance of con- 
tact by area inhabiting rats with alley inhabiting 
rats was brought about through an altered periodic- 
ity of activity by which the area rats tended to 
utilize the periods of decreased activity by the 
alley rats for their own periods of increased activity 
(see pp. 117-119). 
3 . The Strange Object or Strange Situation 
Reaction 
Wild Norway rats are frequently difficult to 
capture when use is made of many of the types of 
commercially available traps. The ineffective- 
ness of such traps is in large part attributable to 
the fact that they represent a new type of object 
in their environment. When the object has become 
somewhat familiar to the rat it may still elicit 
a similar avoidance response if it is placed in a 
new position, particularly a position which in- 
terferes with accustomed activities. The rat re- 
sponds by avoiding the object or situation. Several 
situations were encountered which exemplify this 
reaction. 
A. Activity Recorders. One class of strange ob- 
jects was that formed by devices designed to record 
the activity of rats. The first device was a wire 
suspended along a trail or at a passage through a 
fence. This wire when moved to one side by the 
rat closed a circuit causing a light to flash in the 
observation tower. These wire rods were suspend- 
ed from the center of a square of wood 4 inches in 
width. This square was supported by four wire 
legs and stood some 6 inches above the ground. 
On May 8, 1947, one of these recorders was placed 
at each of the four entrances to the Food Pen. 
The reaction to these recorders was invariably 
the same. The rat would cautiously approach it, 
jump back, bypass it while keeping a foot or two 
away, and then go look at another recorder until 
all four had been examined. No fighting was 
observed around the Food Pen, although rats met 
or passed each other frequently. Gradually the 
number of rats attempting to enter the Food Pen 
lessened. At this time there was considerably 
activity in the alley about the Food Pen. The 
rats did not keep to worn trails. One rat started 
to climb the fence into the Food Pen but only 
went up a foot. The interesting aspect of this 
situation was the reduction of social strife and the 
disruption of normal adherence to trails. At the 
beginning of the following night rats were closing 
the contact recorders without hesitation. This 
indicates that at some time during the previous 
night the rats had learned that no deleterious 
results accompanied brushing by the suspended 
wire rod. 
A much more marked avoidance reaction was 
elicited by another type of activity recorder. As 
mentioned elsewhere (p. 112) these contained a 
photoelectric cell. When a beam of infrared light 
to this cell was interrupted a solenoid closed with a 
sharp clang. The apparatus was protected by a 
black metal tunnel approximately 9 by 12 by 26 
inches. This tunnel formed a strange object, which 
if entered resulted in the production of a strange 
noise. On July 28, 1947, such recorders were 
placed on the inside surface of the Food Pen at each 
of the four entrances. A large amount of garbage 
was placed in the Food Pen as an additional in- 
ducement for the rats to enter. During an hour of 
observation following 6:30 p.m., 7 rats made 27 
responses to these strange objects. The invariable 
response was to approach an entrance to the Food 
85 
