Escalated Aggression

Typically, in response to a threat, an animal will flee or submit to indicate its subordinate status; this bypassing of aggressive behaviors is known as mediated aggression. In contrast, escalated aggression is when the animal challenges the threat with aggressive behaviors. Often the first challenge, by the recipient of the initial threat, will be an aggressive bite. This will then escalate to fighting until one animal either flees or submits, or else is castrated or killed. Escalated aggression is less commonly seen in laboratory settings than mediated aggression due to relatively stable dominance hierarchies and a lack of room for distinct territories. 

Escalated aggression, as the name implies, occurs when neither animal backs down from a threat, so the interaction escalates in intensity and becomes fighting.

Agonistic Interactions

Mediated aggression normally represents the vast majority of mouse agonistic interactions, and is widely misinterpreted in the literature. In contrast, escalated aggression occurs when a subordinate responds to a threat behavior with an aggressive behavior, most typically an aggressive bite. Escalated aggression, as the name implies, escalates until one animal shows flight and submissive behavior, or, in a worst-case scenario, is killed or castrated. (Male mice attempt to castrate each other when they fight, and consequently withdraw their testicles into the body cavity during aggression.)