Figure 52. — Nest made entirely of broom sedge in harborage box 32 on May 10, 1948, by socially low-ranking male 
No. 8. Note that there are fresh feces (dark and shiny) and moldy feces (white) on the bottom of the box but none 
in the nest. 
solitary rats that makes it nearly impossible to say 
with surety that a region suspected of harboring 
no rats, actually does not. 
Rats of both sexes and ranging in age from 25 to 
over 400 days of age have been observed to trans- 
port materials into the harborages. Nest building 
by females is frequently accentuated at about the 
time of parturition. In most cases the newborn 
young were merely observed in a large well built 
nest on the morning following their birth. At such 
times other large new nests were frequently found 
in neighboring harborage boxes, and the inference 
has been made that these were also built by the 
female who gave birth to the observed litter. Such 
bursts of nest building occurred only in association 
with the birth of a litter. In four instances large 
nests were constructed the night prior to that on 
which parturition occurred. When the mother 
with her newborn young were disturbed only to 
the extent of quickly opening and then closing the 
53 
