| Abstract: | Communal litter defence by sister and nonsister female mice can provide a valuable experimental paradigm to test whether females invest preferentially in kin. Since females within sister and nonsister pairs have different coefficients of relatedness with the young, the cumulative litter has more fitness value for related than for unrelated partners. Sister and nonsister paired females that gave birth simultaneously (n = 18), or at least within 7 days from each other (n = 12), were tested for maternal aggression on post partum day 7, or 10 days after the first delivery, respectively. Sister (n = 14) and nonsister pairs (n = 16) did not differ in cumulative values of post partum aggression or in the extent to which aggression was balanced within the pair. The aggressive behavior of each female was not correlated with her relative proportion of pups in the litter. Rather, the combined scores of aggression within the pairs were found to be positively correlated with the cumulative litter size. The analysis of mouse litter defence behavior shows that, under conditions of communal nesting, kinship does not seem to affect parental investment in the young significantly. Rather, the cumulative litter size could be used by paired females as a major indicator for parental investment allocation. |
