Figure 9. — Example of pelage marking, male pelage code No. 18. This male is examining a burrow entrance through which 
a female in estrous has just passed. Rarely do males follow the estrous female into the burrow. Photograph by U.S. 
Army Signal Corps. 
Table 1. — The 43 pelage marking combinations 
possible when no more than two patches of fur are 
removed as shown in figure 8. 
1 
14 
15 
16 
17 
18 
19 
2 
23 
24 
25 
26 
27 
28 
3 
34 
35 
36 
37 
38 
39 
4 
45 
46 
47 
48 
49 
5 
56 
57 
58 
59 
6 
67 
68 
69 
7 
78 
79 
8 
89 
9 
observations for another half-hour or 45 minutes. 
A similar situation existed in relation to sunrise. 
Thus, it was possible to get some good observations 
during at least an hour and a half both in the early 
evening and at daybreak. Since the activity of the 
colony was initiated at least by 6 p.m. regardless 
of the time of sunset, the period available for 
observation was much longer during the warmer 
months of the year (see pp. 112-135). Observa- 
tion during any time of the night was facilitated 
by suspending lamps in certain portions of the pen. 
Four 250-watt lamps were suspended over the 
10 
