as to produce an unusual situation for the study of 
the manner in which rats orient in the absence of 
the perception of previously developed trails. 
Between 8 a.m. and 6 p.m., 5 inches of snow 
fell. This was sufficiently deep to cover over the 
the grass and other vegetation, as well as the de- 
pressions in the vegetation mat, where the trails 
occurred through it. For more than an hour 
before the first rat was observed to be active at 
6:10 p.m. a high wind was sweeping the pen and 
the snow had changed from soft flakes to a hard 
sleet-like condition producing a crust over the 
surface of the snow. This condition of wind and 
snowfall continued through the sequence of first 
activities of the rats which are recorded below. 
By 10 p.m. the snowfall had ceased. 
We shall now examine the movements of the 
first three rats which dug through the snow and 
made excursions across the pen. In order to follow 
this discussion it will be necessary to refer to figure 
14. In addition to trails existing at a later date 
in the history of the colony, this figure shows the 
positions of all the tree trunks, fences, etc. 
First movement: 6:10 p.m. A rat left Hole 15 of 
the North Alley Burrow and proceeded eastward 
through the North Alley and through Passage 3 
across to the outer limiting fence where it entered 
the nearest hole, by digging through the snow, 
of the burrow system which extends along this 
fence opposite Box 14. The interesting thing 
about this route of travel was that the rat passed 
directly by the trunks of seven small trees in an 
identical fashion to the trail existing through the 
vegetation under the snow. By the next morning 
there was a heavily traveled muddy trail over the 
snow along this same route (see fig. 65D) 
Second movement: 6:22 p.m. A rat emerged from 
hole 1 of the South Alley Burrow and proceeded 
by the southwest corner of the Food Pen, a distance 
of approximately 10 feet, and thence along the 
west side of the Food Pen to Passage 8, through 
which it entered the Food Pen. It then went 
directly to the food hopper but without pausing 
turned left at 90° and went to and through Passage 
7 and directly to and by Hole 15 of the North 
Alley Burrow. There were several small pine 
trees about the North Alley Burrow, one of which 
was very close to Hole 15. The rat then proceeded 
eastward along the trail of the first rat but stopped 
in a burrow by Passage 3. This was a route of 
travel exhibited previously by South Alley Bur- 
row rats. 
Third movement: 6:25 p.m. A rat left Box 9, 
crossed over the top of Box 7, circled around Box 
3, dug through the snow to its entry, entered it, 
but soon left and proceeded to Box 2 where it 
behaved likewise. From Box 2 it went by Box 1 
and to Passage 1 and directly across to the position 
of Hole 9 of the South Alley Burrow which was 
covered with snow. Here it paused momentarily 
before going to Hole 1 (the one left by the second 
rat), which it entered momentarily. It then went 
directly to Passage 5 of the Food Pen and thence 
across to the hopper where it ate. 
Conclusion: From these three observations it 
seems apparent that rats can make rapid orien- 
tations which duplicate previously existing routes 
of travel in such a manner as to strongly indicate 
that orientation is a point to point orientation 
between such visible cues as fences, passages 
through fences, and the trunks of trees. Whereas, 
I do not believe that olfaction is utilized in these 
orientations, it may well be that the precise ability 
to dig through the snow into a burrow entry is 
facilitated by olfaction. When several rats live 
in a burrow, there must be some passage of warmer 
scented air through the snow. Thus, when a rat 
arrives at the approximate location of a burrow 
entry a slight pause and sniffing about may reveal 
the exact location. There is no evidence in these 
observations to indicate to what extent, if any, 
kinesthetic perception may play a role in such 
orientations. For further comments on this point 
refer to the discussion (pp. 74 to 78) of the sub- 
nivian trails developed on February 4 to 5, 1948. 
Although these three movements were the only 
ones observed on the evening of January 24, 1948, 
in which rats traveled over the otherwise unmarred 
snow, the trails existing over the snow on the 
morning of January 25 further reveal the nature 
of this orientation. 
Example No. 1 : A path produced by the travel 
of a single rat from Passage 1 through the West 
Alley to Passage 8 of the Food Pen. In figure 14 
it will be noted that the trunks of eight small trees 
protrude through the snow in the West Alley 
between these two passages. The distance be- 
tween these two points is somewhat less than 35 
feet, and I believe that a rat at Passage 1 can 
actually see Passage 8. At least I have seen rats 
turn to avoid another rat which was motionless 
and approximately 25 feet away. If a goal 35 
feet away can be seen by a rat one might suspect 
that it would go directly across the snow between 
72 
