Competition for Milk in the Domestic Rabbit: Survivors Benefit from Littermate Deaths

We sought evidence for postnatal resource limitation among littermates of the domestic rabbit Oryctolagus cuniculus\ and asked whether deaths of individual pups bene_t survivors by increasing their share of milk[ Milk ingestion\ growth and mortality of 09 chinchilla!breed captive litters were recorded between birth and age 10 d[ That milk limits growth and survival was indicated by larger litters showing lower weight gain and higher mortality\ and by a signi_cant positive correlation between milk ingested by individual pups and weight increase[ Within litters\ pups with higher birth weights grew faster\ and weight hierarchies became increasingly stable over the 2 weeks\ suggesting that advantages accrued during gestation were progressively consolidated during lactation[ After individual pups died\ the total daily milk weight obtained by the litter was generally una}ected but per capita milk consumption and growth of surviving pups increased\ and increases in per capita consumption were greater in smaller litters[ The most successful competitors for milk apparently bene_t from the deaths of their littermates by obtaining an increased share of an undiminished daily food supply[ This relation! ship has not previously been demonstrated in any vertebrate[