Copulation increases offensive attack in male rats.

Twenty-four adult male rats with previous sexual experience were tested for aggression against intruders after one of four treatments (n = 6 per treatment): exposure to inaccessible estrous females; exposure to anestrous females; no female exposure, or copulation to ejaculation. Although both exposure to inaccessible estrous females and copulation significantly decreased latency to attack only copulation produced significant elevation of intensity and duration of attack. Results are discussed in reference to the role of aggression in maintaining priority of access to females, and as a means of assuring paternity of offspring by dominant males.