Graphs of plasma catecholamine concentrations measured in healthy, boma-habituated, sub-adult, male white rhinoceros (n = 6), assigned to two treatments administered once each in random order: etorphine-saline (ES, light blue circles) and etorphine-butorphanol (EB, dark blue circles). Blood was collected 30, 40 and 50 min after the rhinoceros became recumbent (t30, t40 and t50, respectively); either 0.9% saline (treatment ES) or butorphanol (treatment EB) were injected IV at t37. The central line within each data set represents the mean, whereas the error bars represent the SD. Refer to Figs 2–6 for graphs of other variables measured or calculated in the rhinoceros. A linear mixed effect model was constructed to assess changes in each of the 29 variables over time within treatments and between treatments. For the purposes of statistical analysis, the ten variables labelled with * on the Y-axis were considered primary outcomes; the 19 others were considered secondary outcomes. For the primary outcomes, alpha was set at 0.05; for the secondary outcomes, alpha was set at 0.05/19 = 0.0026 (a Bonferroni correction for multiple comparisons). In all figures, a solid bar connecting data sets indicates a significant difference, and a dashed bar connecting data sets indicates a significant difference before Bonferroni correction. NB: Differences that lost significance after Bonferroni correction were not considered significant for the purposes of discussion in this paper. The blue arrowhead on the X-axis indicates when saline or butorphanol was administered at t37. The light blue band on the Y-axis of certain graphs indicates the 95% confidence interval for the catecholamine values measured in the non-immobilized rhinoceros or the allometrically calculated values for the etorphine-immobilized rhinoceros.