Introduction and Method
This experiment was designed to compare the effects of food deprivation upon competitive and territorial fighting in rats. We wanted to determine if food deprivation increases territorial fighting in the same way as it increases competitive fighting as shown, to some extent, in Experiment 1. As far as we know, this question has never been addressed in previous literature.
Subjects. Competitive fighting tests were conducted on seven male and eight female DA rats paired with Fischer cagemates of the same sex. The mean weights of the DA males and females were 255 and 206 g, respectively, while the mean weights of the Fischer males and females were 277 and 198 g, respectively.
Territorial fighting tests were conducted on 22 male DA rats paired with DA females and tested with SFD intruder males. The mean weight of the DA males was 276 g, while that of the SFD intruders was 319 g.
Housing and lighting were similar to Experiments 1 and 2.
Experimental design. All animals were tested twice a week with different levels of food deprivation (zero, 12 h, 24 h, 36 h). The levels of deprivation were counterbalanced in order of presentation both within animals (i.e., over repeated testing) and between animals (each animal had a different order), although each animal was tested equally at each of the four levels. It should be noted that the animals were fed after every test in this experiment, unlike in experiment one where 24- and 48-h deprivations were run back to back each week without feeding between them. Whereas in Experiment 1 there was always the same amount of deprivation per week ( 48 h), in this experiment the amount of deprivation per week could vary from as little as 12 to as much as 60 h a week, depending upon the sequence employed.
In the competitive fighting tests, all animals were tested twice at each level of deprivation. Thus, there were 30 tests (two per animal) at each of the four levels of deprivation. In the territorial fighting tests, eight of the animals were tested twice at each of the four levels of deprivation, while the other 14 were tested once at each of the four levels. Thus, for territorial fighting there were also 30 tests at each of the deprivation levels.
Procedures of testing were done in the same way as in Experiments 1 and 2 for competitive and territorial fighting, respectively, and behavioral scoring was also the same.
Statistical analysis. Repeated measures analyses of variance were carried out on both the attack frequency data and the offensive sideways posture frequencies. The main effects were type of test (territorial vs. competitive) and level of food deprivation. The frequency data were not transformed for analysis.