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Introduction
Page 1
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Experiment 1:
Intro/Method
Pages 2-3
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Experiment 1:
Results
Page 4
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Experiment 1:
Discussion
Page 5
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Experiment 2:
Intro/Method
Page 6
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Experiment 2:
Results
Page 7
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Experiment 2:
Discussion
Page 8
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Experiment 3:
Intro/Methods
Page 9
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Experiment 3:
Results
Page 10
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Experiment 3:
Discussion
Page 11
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General Discussion
Page 12
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Figures 1-2-3
Pages 13-14-15
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Tables 1-2-3
Pages 16-17-18
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These results are similar to results obtained by other investigators for territorial fighting. Males attacked male intruders with a mean frequency almost 7 times higher than female intruders. In the study by DeBold and Miczek (9) the equivalent ratio was about 15 times higher according to their Fig. 1. In the study by Brain (8), the rate of attack by males against grouped female intruders was so low that no ratio could be computed. Females attacked females in the present study with a mean frequency over 7 times higher than against male intruders. The equivalent ratio in DeBold and Miczek was quite similar to the present data for their category of female intruders treated with estrogen and progesterone, which is the closest they report to a normal female intruder. In the study by Brain, the attack rate by intact females against normal male intruders was too low to be recorded.
The contrast between competitive fighting and territorial fighting is evident in Fig. 2, where one sees that completely different patterns prevail in the two types of fighting depending upon the sex of the opponent. Whereas territorial fighting is strongly biased towards attacks on the same sex opponents, competitive fighting tends to be stronger against female opponents, perhaps because they are smaller.
Although both competitive and territorial fighting involve the same motor patterns, there are differences in the extent to which they are shown by different sexes against different sex opponents. In the competitive fighting, bite-and-kick attack, bite attack, and offensive sideways posture are shown more or less equally across all categories of test animals and opponents. The only difference is a tendency to show more offensive sideways posture than attack against male opponents, perhaps because they are larger. In the territorial fighting, however, the use of motor patterns is quite different. Males tend to use bite-and-kick attack and offensive sideways posture primarily in their attacks on male intruders, while females tend to use a biting attack in their attacks on female intruders.
We expected that the differential use of certain offense motor patterns might be related to the pregnancy of the females and their use of maternal aggression (3). However, we found the same proportions of each motor pattern in females whether or not they had become pregnant during the course of the experiment.
It is possible that the differential use of motor patterns is related to the spatial arrangements of the cages which differed in the two types of tests employed in Experiments 1 and 2. In Experiment 1, the cage was small and empty and the rats interacted at the food hopper where they jockeyed for access to the food. Both males and females had more or less the same behavior. In Experiment 2, there was a tendency for the males to interact with intruders at the doorway at the center where offensive sideways posture effectively blocked the door or to interact in the open areas where they were able to climb on top of the opponent and deliver a bite-and-kick attack. Females, on the other hand, often encountered the intruder in the tunnel leading to the nest box where the spatial layout precluded the bite-and-kick attack or offensive sideways posture, but left open the possibility of a biting attack, often delivered to the face. This may be similar to the situation in the wild where animals often encounter each other in tunnels and tunnel entrances. DeBold and Miczek (9) also noted higher rates of biting attack by females than by males in territorial fighting experiments.
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