Kin Recognition and Maternal Care under Restricted Feeding in House Mice (Mus domesticus)

Abstract

AbstractThis study tests the hypothesis that female house mice (F1 generation of wild caught Mus domesticus) should preferentially invest in own offspring if confronted with young of different degrees of relatedness. The maternal behaviour of females with litters of 4 own and 4 unrelated alien young (cross‐fostered at day 1 of lactation) was analysed during a lactation period of 22 days both under ad libitum and under restricted feeding (food was restricted by 20%).Cross‐fostering and restricted feeding had no effect on the amount of time spent nursing until weaning. Under both feeding conditions the females did not differ in their maternal behaviour towards own and alien young: there were no significant differences either in the amount of time spent nursing own versus alien pups or in the time spent licking own versus alien young. Weight gain of own and alien = wild littermates did not differ significantly in mixed litters and was similar both under ad libitum and under restricted feeding. Such indiscriminate behaviour might be adaptive if female house mice prefer to communally nest with a relative and thus improve their inclusive fitness by investing in own and related offspring in a communal nest.Under moderate restricted feeding females could not wean the entire litter but reduced litter size by cannibalizing on average 2.7 pups (75% of the pups were killed when they were 4–8 days old). Females with cross‐fostered litters killed as many own as alien young. This suggests that females cannot discriminate between own and unrelated young if cross‐fostering takes place at day 1 of lactation.Besides testing kin recognition abilities, the experiments also allow analysis of the weaning strategy of females under food shortage. Under restricted feeding, body weight of the females was significantly lower during middle lactation than under ad libitum feeding. Weaning weight of young in reduced litters under food restriction (9–10 g) did not differ significantly from weaning weight of young in litters of 7–10 young, but was lower than that of young in similar sized litters (litter size 6), under ad libitum feeding. The maternal behaviour of cannibalizing some young under food shortage can be interpreted as a weaning strategy which results in the largest number of offspring that can be raised to a minimal weaning weight of 9–10 g. Such a weaning strategy might represent a favourable trade‐off between number and size of young produced.