Takahashi L K
Department of Psychology, Rutgers University, New Brunswick, New Jersey 08903 U.S.A.
Behav Processes. 1986 Mar;12(3):237-60. doi: 10.1016/0376-6357(86)90039-2.
Two studies were conducted to determine the importance of the postweaning environment and social milieu in regulating the expression of intraspecific aggression in Norway rats. In Experiment 1, male rats were housed either individually or in pairs at 21 days of age. In addition, one-half of the singly housed and paired animals were given experiences with intruders during maturation. At 85 days of age, all animals were given a brief intruder test and then removed from their postweaning environment and provided individually with homecages for a two week period until tested for aggression toward intruders. Results of intruder tests given during maturation indicated agonistic exchanges appeared earlier and more frequently in cages housing a single resident than cages with cohabiting males. However, agonistic exchanges between singly reared residents and intruders had detrimental consequences in adulthood especially under long-term combat situations. That is, although individually reared animals, with early fighting experiences, were capable of initiating intraspecific aggression, such individuals were unable to defend their homecage over a long period of time as evidenced by the high number of wounds and tendency to lose body weight during adult fighting. In Experiment 2, male Norway rats were reared in pairs from 21 days of age and identified as dominant or subordinate on the basis of intracolony social interactions shown during maturation. At 80 days of age, animals were paired with individually reared males in an unfamiliar cage for a 20 day period and examined for agonistic behavior toward intruders at 100 days of age. Group-reared subordinate males exhibited defensive behavior during confrontations with individually reared animals and incurred more wounds and lost more body weight than their cohabiting partner. In addition, subordinate males showed significantly fewer offensive postures toward intruders than individually reared cohabitants. In contrast, group-reared dominant animals did not differ from individually reared males in display of agonistic patterns, in number of wounds, and body weight changes during the period of cohabitation. These findings demonstrate that early rearing factors have pronounced effects on agonistic behavior. Animals experiencing defeat during development are more likely to lose agonistic confrontations in unfamiliar territory than either animals dominant in their early social interactions or animals without the experience of winning or losing agonistic encounters. These results have implications for the understanding of agonistic behavior and predicting outcomes of animal contests, and reveal important differences in agonistic experiences among animals reared in groups.
进行了两项研究，以确定断奶后环境和社会环境在调节褐家鼠种内攻击行为表达中的重要性。在实验1中，雄性大鼠在21日龄时单独饲养或成对饲养。此外，在成熟过程中，将一半单独饲养和成对饲养的动物与入侵者接触。在85日龄时，对所有动物进行一次简短的入侵者测试，然后将它们从断奶后的环境中移出，并单独提供饲养笼，为期两周，直到测试它们对入侵者的攻击性。成熟过程中进行的入侵者测试结果表明，与同居雄性的笼子相比，单独饲养一只大鼠的笼子里出现争斗性交流的时间更早且更频繁。然而，单独饲养的大鼠与入侵者之间的争斗性交流在成年期会产生有害后果，尤其是在长期战斗的情况下。也就是说，虽然单独饲养且有早期战斗经历的动物能够发起种内攻击，但这些个体在成年战斗期间无法长时间保卫自己的饲养笼，这从成年战斗期间大量的伤口以及体重减轻的趋势可以看出。在实验2中，雄性褐家鼠从21日龄开始成对饲养，并根据成熟过程中群体内社会互动表现确定为主导或从属。在80日龄时，将动物与单独饲养的雄性在一个陌生的笼子里配对20天，并在100日龄时检查它们对入侵者的争斗行为。群体饲养的从属雄性在与单独饲养的动物对抗时表现出防御行为，并且比它们的同居伙伴受伤更多、体重减轻更多。此外，从属雄性对入侵者表现出的进攻姿势明显少于单独饲养的同居者。相比之下，群体饲养的主导动物在同居期间的争斗模式表现、伤口数量和体重变化方面与单独饲养的雄性没有差异。这些发现表明，早期饲养因素对争斗行为有显著影响。在发育过程中经历失败的动物，在陌生领地中比在早期社会互动中占主导地位的动物或没有输赢争斗经历的动物更有可能在争斗对抗中失败。这些结果对于理解争斗行为和预测动物竞争结果具有启示意义，并揭示了群体饲养动物之间争斗经历的重要差异。
