Results/Conclusions Our model successfully estimated the lipid mass of female southern elephant seals while at sea, under certain assumptions pertaining to the females’ lean mass. Given a viable predictor of elephant seal condition, we simulated disturbance by excluding females from preferred feeding grounds, which would result in increased movement and decreased energy intake. Increasing the duration of the disturbance successively decreased female lipid mass. This led to a decrease in pup weaning mass, reducing pup survival. Large changes in maternal lipid mass were needed to significantly reduce pup weaning mass, so pup survival did not fluctuate widely. The duration of the disturbance, combined with the proportion of the population exposed to its effects, determined the magnitude of the impact on the vital rate for the population. Relatively small declines in overall pup survival resulting from realistic disturbance scenarios have the potential to negatively impact the population. This has conservation implications, since widespread, minor disturbances could affect species abundance.