A DESCRIPTION OF THE ONTOGENY OF MOUSE AGONISTIC BEHAVIOR

The development of agonistic behavior was characterized in outbred Swi ss CD-1 male Mus domesticus. At weaning (postnatal day [PND] 21), mice were housed either individually or as male pairs. Social encounters w ere carried out between dyads of initially unfamiliar same-age and sam e-housing subjects every 3rd day, from PND 23 to 47. The majority of b oth offensive and defensive elements had their onset around PND 29. Ov erall, their expression increased around puberty (i.e., on PND 35), wh ich also represented the peak of an inverted U-shaped profile for the frequency of the ''ambivalent'' tail rattling behavior. A stability of dominance submission relationships over development appeared, and ear ly short latencies to display either the first crouched posture (subor dinate) or the first attack (dominant) turned out to be possible predi ctors of adult social status. Ongoing individual housing was associate d with a greater expression and an earlier onset of fighting behavior.