Different test situations for measuring offensive aggression in male rats do not result in the same wound pattern.

It has been reported by the Blanchards, that the attacks of offensively motivated rats produce a very characteristic wound distribution on the body of opponents, the back region being the most prominent target area. We now report that the distribution of wounds on male intruders produced by male resident Wistar rats in a resident-intruder paradigm, depends on the experimental situation used. Rats solitarily housed in small cages (0.1 m2), produced most wounds (57%) on the upper back, about 14% on the lower back, whereas head and belly were much less bitten. Rats housed in larger cages (0.52 m2) with a female ("territorial situation") produced about 39% of the wounds on the back, equally divided over the anterior and posterior parts. In this situation the head (21%) and the belly (23%) were more frequently bitten than in the other test situations. In a large colony (5.7 m2), practically all wounds were situated dorsally (81%), the majority (58.5%) on the lower part of the back. It was concluded that the distribution of wounds over the body of the intruder was at least partly determined by the possibility of escape.