Fig. 4

Ecological trends in babesial infection. a Standardized mass (in grams; y-axis) by forearm length (in mm; x-axis) for all adult male P. rufus fruit bats in our dataset (closed circles; infected = orange, uninfected = blue). Best-fit line from the fitted ‘standard major axis linear regression’ shown in black. R² of the fitted model with predictor variables of forearm length and infection status (a factor) = 0.53. b Boxplot showing mean and interquartile range of forearm: standardized mass residual for babesiae-negative (neg., blue) and -positive (pos., orange) bats. Positive bats displayed a significantly higher residual by Wilcoxon rank sum test with continuity correction (W = 165, P = 0.039). c FOI estimated from best-fit SI model to age-prevalence data (mean = 0.0067; 95% CI by SE: 0.033–0.133). d Age-prevalence trends in babesial infection from raw data (open circles with 95% binomial exact CIs shown as dotted vertical lines) and fitted SI model (solid orange line = mean model output; translucent shading = 95% CI by SE)