Conspecific aggression in the laboratory rat

Area of Science:

• Ethology
• Animal Behavior
• Mammalian Aggression

Background:

• Dominant male rodents often display aggression towards intruders.
• Understanding aggression in domesticated species is crucial for welfare and research.

Purpose of the Study:

• To investigate the nature and severity of attacks by dominant male domesticated rats on conspecific strangers.
• To determine the distribution of bite lesions and the lethality of these aggressive encounters.

Main Methods:

• Introduction of unfamiliar male rats (strangers) into established colonies of dominant male domesticated rats.
• Observation of threat displays and biting attacks.
• Analysis of lesion distribution on attacked rats (anesthetized vs. unanesthetized).
• Monitoring survival rates of introduced strangers over several days.

Main Results:

• Dominant males engaged in both threat displays and biting attacks on strangers.
• Bites were nonrandomly distributed, primarily affecting the head and upper back.
• 66% of introduced strangers were killed, indicating lethal aggression without external provocation.

Conclusions:

• Domesticated rats exhibit significant intraspecific aggression, including lethal attacks.
• Aggression patterns suggest specific targeting, with head and upper back being vulnerable areas.
• These findings highlight the potential for severe harm in social encounters within this domesticated strain.