Increase in aggressiveness of male mice after irradiation of paternal spermatozoa with 600 R of gamma-rays as dependent on fertility.

The agonistic behavior of unexperienced pairs of NMRI male mice was determined by counting the bites received from and delivered to the opponent within 24 hr. The first 10 min of agonistic encounters was recorded by video tape to analyze the frequency and duration of ten behavioral traits. Each pair consisted of two F1 males, one of which was derived from paternal spermatozoa irradiated with 600 R of gamma-rays (600-F1), while the other stemmed from a sham-treated father (control-F1). The 600-F1 males exhibited higher aggressiveness than their control F1 counterparts, in which the sterile and semisterile males (presumed to be translocation heterozygotes) showed a higher level of agonistic behavior and overall activity than the normally fertile F1 males of the same group. 600-F1 males released more urine drops than the control males. No significant differences between 600-F1 and control-F1 males or between fertile and sterile plus semisterile males were found for learning ability.