Parental care, sibling relationships and the development of aggressive behaviour in two lines of wild house mice

Adult males from one line (Short Attack Latency = SAL line) are more aggressive, show less sensitivity to changes in their environment and behave in a more internally controlled, routine-like way, than do males from the other line (outbred=Control line). Paternal care did not differ between the two lines, but SAL pups received higher levels of nursing and general maternal care than did Control pups, and they appeared to be weaned later. Despite these differences, SAL pups grew more slowly, suggesting that their high levels of sucking behaviour were a reflection of high milk demand, perhaps due to a low milk supply, rather than high milk intake. From day 32 onwards, SAL pups began to show higher levels of aggression towards each other than did Control pups. SAL males developed into faster attackers than Control males and, in SAL litters, intra-litter variation in attack speed was strongly influenced by preceding experience of sibling aggression. Inadequate nutrition of young SAL pups, mediated through the mother may promote increased competition for access to the mother's nipples and predispose pups to develop into more active/competitive individuals. (See also 92L/07305). -from Authors