MATERNAL EFFECTS ON THE DEVELOPMENT OF SOCIAL RANK AND IMMUNITY TRADE-OFFS IN MALE LABORATORY MICE (MUS MUSCULUS)

Social status in randomly constituted groups of male CFLP :mice was pr edictable from early suckling behaviour and rate of weight gain in nat al litters. High-ranking males were those that had suckled on more ant erior teats and gained weight more quickly. Rank was not predicted by an)I measures of sibling interaction or hormone (testosterone, cortico sterone) concentration. Aggressiveness in eventual high-rankers was as sociated negatively with the proportion of Males in the litter at birt h and the amount of maternal attention received. Aggressive social rel ationships within natal litters did not predict polarized rank relatio nships in randomized groups. Nevertheless, while still in their natal litters, and in the absence of aggressive rank relationships, eventual rank categories showed the same difference in modulation of testoster one concentration in relation to current immunocompetence (low-rankers modulating, high-rankers not), as has repeatedly been found in random ized groups by earlier studies. The role of maternal condition in dete rmining rank-related life-history development in male mice is discusse d.