Parasites in good state increase conversion rates as RBC densities increase.

RBC density was perturbed independently of parasite state for P. chabaudi parasites exposed to EPO (A, days 4–14 PI) or phenylhydrazine (B, day 1 PI). Change in RBC refers to the difference in RBC density between the decision-making and parental cohorts of asexuals. Parasites were in good state during treatments in both experiments, with >90% exceeding a replication rate of 1.61 (A) or 3.3 (B). Note, conversion in (A) is estimated following [54], while a simpler metric had to be used for (B) (see ‘Experiments’ in Materials and methods). Lines and shaded areas are predictions ± SEM from generalised additive models for conversion as a function of changes in RBC density.