Fostering in the African striped mouse: implications for kin recognition and dominance

Fostering was studied in the African striped mouse Rhabdomys pumilio (Sparrman, 1784) in captivity to establish if females can distinguish their own from Strange pups, and if fostering affected the biology of fostered pups. In experiment 1, I exchanged 3-4 same-age pups between two litters; their acceptance by the foster mother and their growth rate were studied from 0 to 16 days of age. In experiment 2, the acceptance of pups fostered at 2 days of age and returned to their natural mothers between 4 and 16 days of age was ascertained. All pups younger than 10 and 12 days of age were accepted in experiment 1 and 2, respectively. Slow growth rates were recorded only for pups fostered at 10 days old. Females appeared not to distinguish their own pups from strange pups, until the pups started eating solid food. In experiment 3, the dominance-subordinate relationship between sexually mature fostered and normally-reared individuals was established in dyadic encounters. Pups fostered at 4-6 days were equally likely to win or lose an encounter, whereas pups fostered at 8-10 days were significantly more likely to win an encounter. It appears that fostering affects the later dominant behaviour of some fostered young.