Table 41 . — Characteristics of rats engaged in paired conflict situations 
Sex 
Type of pairing 
N 
Means : 
Age in 
days 
: 2 standarc 
Weight 
in grams 
deviations 
Number of 
wounds 
Maturity 1 
index 
M 
Winner 
67 
371 ± 158 
480± 122 
7. 2± 11. 8 
I. 64 
M 
Loser 
67 
285±270 
427± 122 
6. 2 ± 1 3. 4 
I. 68 
M 
Winner 
4 
248 
489 
3. 8 
I. 71 
F 
Loser 
4 
305 
376 
12. 5 
I. 76 
F 
Winner . 
29 
304± 158 
412± 164 
2. 5± 5.0 
I. 59 
F 
Loser 
29 
289± 228 
373± 176 
9. 6± 12. 1 
II. 09 
F 
Winner 
29 
298± 152 
408 ± 98 
2. 4± 4.8 
I. 49 
M 
Loser 
29 
340 ±398 
406 ±150 
7. 6± 15. 4 
I. 54 
M 
Winner (Loser unknown) 
37 
383 
499 
11. 5 
I. 31 
M 
Loser (Winner unknown) 
9 
398 
443 
8. 1 
I. 96 
F 
Winner (Loser unknown) 
13 
348 
440 
2. 3 
I. 77 
F 
Loser (Winner unknown) 
10 
310 
376 
11. 5 
II. 05 
Total of M winners 
108 
371 ±142 
486± 128 
8. 6± 9.4 
I. 51 
Total of M losers 
105 
310± 230 
421 ±144 
6. 9± 14. 2 
I. 68 
Total of F winners 
71 
310 ± 150 
416± 124 
2. 5± 4. 6 
I. 62 
Total of F losers 
43 
296±232 
373± 154 
10. 4± 16. 0 
II. 05 
1 The number of animals for which data on wounds or maturity index were available was somewhat less than for age 
and weight. 
tically never fought back. Among females there 
were also a few such individuals as these latter 
males, and they formed by far the bulk of the 
females which lost combats. Female winners were 
characterized by few wounds since they rarely 
engaged in combat except under situations in 
which the opponent did not fight back. The 
generally lower number of wounds in females 
than on males is particularly well shown in Figure 
122 . 
b. Age and size. The typically small combat- 
incurred wounds healed within 2-weeks time. 
Thus, by the time a rat was retrapped during a 
later trapping period the wounds recorded repre- 
sented those received in recent combat. There- 
fore, it was possible to construct figure 122 showing 
the change in mean number of wounds with age. 
Six clear-cut periods are discernible for each sex. 
Each period is characterized by a specific rate of 
change in the mean number of wounds. These 
changes may be viewed as an indication of the 
maturation of aggressive behavior. 
Period one, when no wounds were received, 
lasted to about 40 days of age and coincided with 
the time of nursing and close association with the 
mother. Period 2, circa 40 to 60 days of age was 
the time the maternal ties were beginning to 
break, and a very few individuals received their 
first wound. Period 3, lasting from 60 to 115 
days of age for males and to 150 days of age for 
females, is the time during which most individuals 
receive their first wounds. For males, this coincides 
with the period of sexual maturation to the point 
of exhibiting the nearly complete repertoire of 
courtship and copulatory behavior. Period 3 may 
also correspond to sexual maturation in the female 
since it was quite apparent that females under 115 
days of age were not so frequently as attractive to 
males as were older females. Although the rate 
of increase in aggression was slower for females, 
Period 3 terminated at approximately the same 
mean wound level as for males. 
There is no plausible explanation as to why 
there was no apparent change in intensity of 
189 
