in the West Alley. Then female 20 took it 
to near Passage 4. At this point she dropped 
it upon being chased by another rat. Thus, 
this food after transportation by three separ- 
ate rats was available for a fourth rat. 
7. June 28, 1948. Female 28 (316 days of age) 
took a cookie that another rat had left at Pas- 
sage 5 of the Food Pen and carried it up Path 
1 and over into Area I. Along the way up 
Path 1 some of the cookie broke off and then 
Male 82 (112 days of age) came by and cleaned 
up the crumbs. One-hundred and two- 
day-old female 75 also came by and ate some 
of these crumbs. 
This food dispersal becomes so extensive during 
the night that on the next day it may be found in 
locations where no rats are harboring even near by. 
Twice a considerable number of Purina checkers 
were found in Area I, where they had been trans- 
ported during the previous night, although during 
the hours of daylight no animals were inhabiting 
this Area. 
During November and December 1948 a record 
was kept of the rate of removal of Purina checkers 
from the hopper. Eight-hundred pounds were 
removed during 37 days. Approximate data: 
Number of rats 144 
Mean weight 400 grams 
Grams of food removed per 
rat per night 60.5 
Purina checkers removed per 
rat per night 20 plus (the checkers av- 
eraged less than 3 g. 
each) 
Since occasionally 1 to 3 days elapsed between 
the time each 100 pound lot of food was removed 
from the hopper and the next was placed, there 
actually was a period of 52 days between the pro- 
vision of the first 100 pounds and the removal of the 
eighth 100 pounds. Considering this span of time, 
an average of 47.6 grams of food was removed per 
rat per night. This is equivalent to 0.119 grams of 
food per night per gram of rat. This includes both 
food consumed and food wasted. 
Dr. Olaf Mickelson (Laboratory of Nutrition and 
Endocrinology of the National Institutes of Health) 
informs me that 0.05 grams of food (of the Purina 
chow type such as I used for the rats in the pen) per 
gram of body weight approximates that used each 
day by 400 gram rats. Considering the fact that 
over twice this amount was removed by the rats 
and dispersed through the pen, the likelihood was 
that all rats secured adequate food. 
D. Factors Affecting the Intensity of Storage. No 
rats under 40 days of age were observed to trans- 
port food from the Food Pen. Between the ages of 
25 and 40 days most of the explorations of the young 
were confined to within 10 feet of the home burrow 
or harborage box. Very shortly after the 40th 
day of life most of the young reach the Food Pan. 
Coincident with this arrival at the food source the 
behavior of transporting food immediately appears 
quite well developed, but its orientation with 
reference to harborage sites is poorly developed. 
For example: 
July 11, 1947. In the evening I entered the 
observation tower at 6:15 p.m. At that time a 
42-day-old Litter 3 rat whose home was in Area 
III was carrying Purina checkers from the Food 
Pen into the East Alley. At 6:28 p.m. I began 
counting the trips: 6:28 to 6:47, 36 trips; 6:55 to 
7 :00, 10 trips. It dashes from the weeds in the East 
Alley to the tile at Passage 6; there it pauses for 
3 to 10 seconds with its head protruding into the 
Food Pen. It then dashes to the food tray, gets a 
Purina checker and dashes back into ihe East 
Alley through the tile at Passage 6 without pausing. 
It began raining lightly at 6:22 p.m., but this did 
not seem to disturb this little rat. There is an 
abundance of fresh garbage in the Food Pen 
toward which this rat paid no attention. This is 
the first Litter 3 rat that has been seen in the 
Food Pen. The next morning 42 checkers were 
found in the East Alley where this rat had been 
going. There were three piles: 30, 11, 1. 
Between the 40th and 60th day of age most of 
the food transported is left as caches in shelters 
either at the passages into the Food Pen or just 
peripheral to it. Beginning with the 60th day 
there is a gradual elaboration of the storage be- 
havior so that by the 100th day this behavior 
is in essentially its adult stage in so far as the 
likelihood of reaching a harborage with the trans- 
ported food is concerned. The 60th day of age 
approximately marks the time when the young 
become independent of their mother to the extent 
that they may shift their center of activity else- 
where. It also marks the time when they begin 
to lose the juvenile pelage. On the other hand 
the 100th day of life falls roughly at the time of 
the completion of the adult pelage and the ex- 
pression of adult sexual behavior. 
Both sexes store food from that time until death. 
However, males store considerable less frequently 
than do females. The increased storage activity 
676-768 O — 63 8 
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