Attack and defense in laboratory and wild Norway and black rats.

Intra- and interspecific agonistic encounters in Long-Evans and field-trapped Rattus norvegicus and Rattus rattus showed a consistency in the form and character of attack and defensive behaviors. Colony alpha males exhibited high levels of lateral attack, on-top, and chasing behaviors which resulted in a high percentage of bites on the intruder's back. Bites directed to the back were countered by intruders through the utilization of boxing, on-back, and flight defense. These findings indicate that agonistic interactions in Rattus are underlined by back-attack and back-defense strategies. A sex difference in biting was also consistent across strains: males bit the back and flanks and females the head of an anesthetized stranger which suggest differences in the motivation of male and female attack.