Aggression and social experience in domesticated rats

Area of Science:

• Ethology
• Animal Behavior
• Neuroscience

Background:

• Social isolation in early development can alter adult behavior.
• Social interactions are critical for normal behavioral development in many species.
• Aggression is a complex behavior influenced by both individual history and social context.

Purpose of the Study:

• To investigate the impact of social rearing history on inter-rat aggression.
• To determine how the social experience of both resident and intruder rats affects aggressive encounters.
• To elucidate the role of social experience in the development of aggressive behaviors.

Main Methods:

• Establishing rat colonies with either continuous social experience or isolation since weaning.
• Introducing unfamiliar "intruder" rats, with or without postweaning social experience, to established colonies.
• Conducting behavioral observations and assessing intruder physical condition (injuries, weight loss) over a 21-hour period.

Main Results:

• Serious fighting, physical injuries, and significant weight loss occurred exclusively when isolation-reared intruders were introduced to colonies of socially experienced rats.
• Rats with postweaning social experience, whether as residents or intruders, exhibited reduced aggression.
• The outcome of aggressive encounters was dependent on the social history of both the colony and the intruder.

Conclusions:

• Aggression is a joint function of the rearing history of the colony and the intruder.
• Social experience is a critical factor in the behavioral development and modulation of aggression in rats.
• Early social environment significantly influences an individual's propensity for aggression in social encounters.