Effects of the type of intergroup conflict on urinary oxytocin levels in wild chimpanzees in East and South groups (n = 345 samples, 16 subjects, 194 events). Shown are medians (thin horizontal lines), quartiles (boxes), percentiles (2.5 and 97.5%; vertical lines), minimum and maximum (laying crosses), as well as the fitted model and its 95% confidence intervals (thick lines). ***P < 0.001.