Alley Burrow. At any rate, her young after wean- 
ing seemed to utilize both of these burrow systems. 
One of these young, female 15, conceived as a 
young adult on the same date as her mother. Their 
litters were both born on the same date, August 16, 
1947. Prior to this, when female 15 was 90 days of 
age, she was seen to be chased by female 10. Al- 
though this was the only observed aggressive en- 
counter between these two females it is highly 
probable that the younger, smaller female 15 held 
a more subordinate status. In line with this sub- 
ordinate status her litter (L-6) was born at the 
North Alley Burrow, whereas female 10 had her 
litter (L-5) at the South Alley Burrow. 
With this introduction we may now return to 
the examination of the genealogical record (fig. 
102). In the first place only one of the five 
colonizing females had descendants which pro- 
duced surviving litters during 1949. Furthermore, 
this single female produced two line of descendents. 
GENEALOGY 
?io $ ii 
Figure 102. — Genealogy of colony. The lines of descent are based entirely on mothers, since fathers could not be determined 
with any degree of assurance. Litter number, place, and date of birth is given above the row of numbers designating the 
eartags of the weaned members of the litter. Lines extend upward from the litter to the mother. Where two or more litters 
were born on about the same date at the same place, it was possible only to designate which females were involved as 
mothers, but not which females were the mother of which members of the composite litter. Rats whose eartag numbers are 
enclosed in rectangles died before 150 days of age. See table 66 for growth rates of rats living less or more than 150 
days All others lived longer than this. Those whose numbers are underlined were still alive May 1 7, 1949, when the 
process of killing or the colony began. I, II, III, and IV refei to birth in one of the four triangular areas. NAB and SAB 
refer to birth at the North or South Alley Burrow. TlB - passage 1 extension of the South Alley Burrow (see fig. 21). 
WA West Alley L & P refer to state of lactation and pregnancy at time rats were killed in May 1949. Males 384 
and 773 referred to in figure 112 are not included on the genealogy chart. 
140 
