these points. This however, was not the case. 
Instead the route of travel was roughly sigmoid in 
nature and made in such a way that it approached 
six of these tree trunks about as close as it was pos- 
sible for the rat to travel. If these trees are num- 
bered from 1 to 8 from Passage 1, the travel was: 
Directly to the left of trees 1 and 2, 2 feet to the 
right of tree 3, directly to the right of tree 4, 
6 feet to the left of tree 5, directly to the left of 
trees 6, 7 and 8, and thence to Passage 8. One 
might suggest that the orientation toward the 
trees is for the purpose of their protective cover. 
However, I suspect this is not likely the case since 
three of the trees were bare deciduous ones. 
The orientation between trees 6, 7, and 8 is particu- 
larly instructive. Trees 6 and 8 were small pines 
whereas tree 7 was a dogwood. Had the rat been 
traveling between points of protective cover alone 
it would not have bent back to tree 7 which took 
it away from the most direct route of travel. 
Other similar instances could be cited but this one 
is typical. 
On two later occasions (January 30 and February 
1, 1949) the first rat in the evening to travel over 
new fallen snow between Passages 1 and 8 was ob- 
served. By these dates a post had been placed in 
the ground in the West Alley about half way be- 
tween Passage 1 and tree 1. On each of these 
occasions the rat left Passage 1 and ran just to the 
right of the post and just to the right of trees 5 and 
7 and to the left of tree 8 and thence to Passage 8. 
This route of travel formed essentially a straight 
line between the two passages. In each case the 
other rats who traveled between these two points 
followed identical routes so that by the next 
morning the surface of the snow was covered with 
a narrow muddy ribbon. 
Example No. 2: Path between Box 1 in Area I 
and Passage 1. Prior and following the various 
snowfalls there was a single arched trail of travel 
between these two points. From Box 1 the trail 
led for a distance of about 5 feet through a group 
of bare stalks of the goldenrod plant. Each stalk 
was about one-quarter inch in diameter. Two 
feet beyond this clump of stalks the trail passed 
just to the right of one small tree and then 18 
inches farther on it passed just to the left of the 
trunk of another small tree. From the latter the 
trail kept along a very slightly bent arch for a 
little over 6 feet, to Passage 1. This is shown in 
figure 68. The point of interest here is the reaction 
of the rats to the system of physical cues existing 
Figure 68. — Trail over ground during fall of 1947 and during 
the following winter. The same pattern developed after 
a 1-inch snow on January 14, 1948. However, after a 
5-inch snow on January 25, 1948, the rats were unable to 
duplicate that section of the trail which passed through the 
group of vertical goldenrod stalks. See figure 69. 
along this trail on the night of January 24-25 
when the trail itself and the low-lying vegetation 
was obscured by the snow. There was a single 
trail over the approximately 12 inches from the 
exit from Box 1 to the beginning of the clump of 
goldenrod stalks. At the edge of the clump of 
stalks the trail diverged into several trails which 
reconverged 5 feet farther along at the opposite 
edge of the clump. From that point on the trail 
was essentially the same as had existed previously. 
The conclusion drawn from this is that rats are 
unable to utilize a large number of cues for orient- 
ing their path of travel over a short distance. 
When the snow was not on the ground it must have 
been that the rats utilized visual, tactile, and 
olfactory cues to the trail itself in following it 
rather than orienting to the many vertical cues 
provided by the stalks of the goldenrod stems. 
A portion of this diverging trail is shown in the 
photograph in figure 69. During the next two 
nights the rats gradually concentrated their travel 
along one of these trails until it all lay along a single 
route slightly SW of the trail which existed on the 
ground under the snow. Thus through trial and 
error a new trail developed to which the rats were 
able to respond directly by visual, tactile or 
olfactory perception. 
Example No. 3: Trail to Passage 3 from a burrow 
exit beside the outside fence. The trail on the 
ground covered a distance of approximately 12 
feet over the ground devoid of any vegetation or 
any other structures. As shown in figure 70, the 
trail followed a curved course for the first half of 
the distance from the fence. On the morning of 
January 25, 1948, there was a system of trails over 
the most curved portion of the trail. The con- 
clusion is that without any tactile or visual cues, or 
possible olfactory ones, a rat is unable to reproduce 
676-768 O — 63- 
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